Help Troubleshooting Fuel Delivery...

Hi,

I've been chasing a strange shuddering for a while. I think many of us experienced a mild shudder at ~70mph after switching to larger injectors. We often solved that by adjusting the IQ to about 5mg/s. THIS shudder is much worse and occurs at various RPM and appears to be associated only with a medium load such as cruising over rolling hills or towing a light trailer. My new shuddering appeared immediately after swapping out an experimental turbo in favor of a stock turbo. For the record, I'm not pointing fingers at any tuners. I'm just providing a bit of history.

1) The shuddering was evident the day I returned to the stock turbo and began using my RC3 software. I'll admit I suspected the new software since the problem did not appear to be an issue when using my older UP2 program.

2) The shuddering is very persistent on rolling hills and using cruise control is out of the question since I have to "modulate" the go pedal to avoid the shudder on any sort of hills or while towing. It gets REALLY old after a hundred mile. It would be unbearable on a 1000-mile trip. As a result, I drove on my UP2 program for a while since I was doing a lot of long distance driving.

3) The problem did not seem to be an issue during the winter; but returned this spring when the temps rose. In fact, the problem appears to be even worse this year since the shuddering now occurs with both my RC3 AND UP2 programs.

4) Since all was well before my turbo experiment, I decided to chase down anything that had changed in the process. I could think of three things that were different: The catalytic converter (not suspected since it's newer than the one I removed and the turbo spools FAST), IQ was set at 3-mg/s, and I added PP520s (was running B205s prior to that). Adjusting IQ was my first move since I wasn't a fan of setting it at 3-mg/s. I tried various settings between 3-11 with no change in anything but smoke and power. Shuddering was present at all settings. Then I borrowed a set of stock A4 fuel injectors from Paramedick (thanks, Bruce!). WOW! Power is down but the shuddering disappeared. Highway driving is peaceful for the first time in over a year. Although I checked the injector pop pressures twice and saw they were all the same, I suspected there might have been either a nozzle mismatch or something internal to the injector.

5) But now that I've driven in HILLS at high speeds, I now know the shuddering is only greatly reduced, NOT eliminated. It now seems the shudder happens at a higher load than it did with the PP520s. For example, shuddering used to happen when the load was around 7-psi. Now it takes a steady load around 12-psi to induce shuddering. Naturally, I didn't discover this until I drove on some hills at higher speeds. Although my shuddering is gone unless I find that "critical zone" in which it happens, I still wonder if there's something going on with my injection pump. I can't keep Bruce's injectors forever; so I need to get to the bottom of things.

Here are some other observations:

1) The problem seemed to be worse when summer came. However, the problem exists whether the engine is hot or cold, morning or afternoon.

2) Slow-down shudder is pretty bad.

3) Block #2 in basic settings fluctuates quite a bit... perhaps as much as 5-8 points.

4) Block #9 frequently reads over 170. I haven't checked it in the morning yet. But I set block #2 to read 52 the last time I set IP timing and that put my reading right in the center of the graph (I don't have the graph before me; so I don't know what #9 read that day). I checked the IP timing last week and #2 was 40 and #9 was 179. Although #2 seems REALLY low, this setting still put things right in the middle of the graph.

5) Since the problem is worse now than it was last year, I figure whatever is happening is the result of a degrading part.

6) All symptoms are greatly reduced with the stock B184 injectors. The slow-down shudder is present; but not as obnoxious. The dreaded highway shudder only appears when climbing a hill around 75-mph (I'm going to put about 300-lbs of stuff in the trunk and see what happens at 60-mph).

7) The car drives fine under 45-mph in 4th gear (light load) or balls out while autocrossing or passing/merging (heavy load). The problem only exists during medium loads (mild acceleration, hills, or towing).

8) OH, in addition to the shuddering, the engine "lobes" or rocks in the engine bay when allowed to idle for more than about 30-seconds.

I have a few theories, #1 from a TDIClubber, #2 and #3 hypothesized from research here:

1) IP is "leaking" internally. This is speculated by the fluctuation in block #2. The quantity adjuster cannot properly regulate fuel.

2) Fuel temperature sensor needs replacing. The abnormally high temp reading is causing the car to run "retarded." But that doesn't explain why things are fine at light loads (at least not for me... not yet).

3) My Epsilonian Device could be suspect. The TDIFAQ says this(edited for brevity): "Some vehicles may have had a device fitted in the electrical circuit from the MAF sensor to the ECU, which tricks the computer into thinking that the EGR system is operating when in fact, it is disconnected in order to avoid intake clogging, thus avoiding a MIL or "check engine" light. Malfunction of this device can cause shuddering under certain speed and load conditions. Check security of electrical connections associated with this device, if the vehicle is so equipped. Calibration of the vacuum switch may have some effect... If the vehicle is modified beyond stock, the modifications may be such that the ECU in the vehicle is not compatible with the modifications. In some cases, modifications to greatly increase the amount of fuel delivery have resulted in shuddering... But in extreme cases, the only solution to the shuddering may involve un-doing some of the modifications so that the ECU is capable of dealing with the situation."

I guess my next move should be to unplug the vacuum hose from the EPS device. This will result in a MIL, but the ECU will read actual MAF readings instead of those altered by the EPS device. I'll report the outcome of this after my drive to MD. Could the EPS device cause my funky idling issue?

Any advice and/or recommendations would be greatly appreciated.

Thanks,

Scott

PS: Would this topic get more exposure in the Power Enhancements section since some of my enhancements could be the cause and this issue could be common to A3 AND A4 owners? Or is it fine here? We A3/B4 guys seems to be a dying breed.

Scott, I would cross-post in the power section (I can't believe I'm saying this!). Definitely would be seen by more eyes.

I am intrigued by the Eps idea. It's possible.

Don't worry about hurrying with the injectors. I don't need them right now. Keep them for another month or so until you sort this out.

Bruce

Thanks, Bruce!

BTW, I drove my 160-miles through rolling hills to MD with about 350-lbs in the trunk. I was only able to induce a shudder once or twice and it was VERY light... something we old-timers would consider normal in a modified A3 TDI. Perhaps the PP520s are just too much for this car. But I still want to investigate further. I'll try inducing again during my commute tomorrow. THEN I'll try unplugging the EPS device so I can test again on the same stretch of road.

Scott

Which turbo did you change from/too , it all does sound as if your running to much fuel and i would agree on changing out the fuel temp sensor with a new one.

It could also be a bad No 3 injector connection , and have you recently done a TB change........it may have slipped , i remember changing out the gt15 with the t25 and once where i had a shudder with the gt15 and a certain chip i didn't have the same with the larger t25 turbo.

With out knowing which i think i do you have changed back to a smaller turbo have you not , and even with the larger unit you still had this shudder although to a lesser extent.........there seems to be to many mods in the mix to like the maf one especially......why!!!.

Hi,

I guess it would help to post more details on the car itself:

1) 206,000-miles on engine and IP.

2) ~80,000-miles on the B205 injector bodies and ~20,000-miles on the PP520s that were swapped onto the bodies (borrowed B184 injectors have ~3000-miles according to markings on the boxes). Shuddering with the PP520s is horrible. Shuddering with the B184s is light, but tolerable. UP2 shudders less than RC3. Shuddering seems to be worse with more fuel-related upgrades.

3) Currently running RC3 software.

4) My turbo is STOCK. My other turbo was a T3. But that doesn't matter. I never got it to work properly. The issue at hand is with the stock K03.

5) Timing belt has about 50,000-miles on it. I usually change them out every 50-55k. I'm holding off for now in case I need to do an IP at the same time.

The rest of the engine is stock with the exception of NO EGR (and EPS mode to compensate). Please let me know if you need any more info.

Thanks!

Scott

Scott, I don't know if this really applies to your A3... but I have noticed that the slow down shudder, which was very present even with stock nozzles and stock software, is totally gone with the rocketchip II / III switchable program I got.

Does you car shudder with the stock software? I see that it shudders with the UPS as well so that would tend to rule out the RC...

I would get the EPS device out of there and see what that does. And doesn't your RC have an EGR delete in it anyway?

-Jason

An update:

The shudder is VERY difficult to produce at speeds under 65-mph with the stock injectors. But it does return when cruising faster or when towing on the highway. I unplugged the vacuum hose from the EPS device with no change. I'll admit I didn't REMOVE it. But since the wiring is electrically stock-like without the hose connected, it seems reasonable to speculate the EPS device is not at fault. I could still try some resistance measurements on the device itself. But I think I'd get a MAF fault code if it was a wiring issue.

I also went ahead and did some VAG-COM readings. Outside temperature was 90*F. Here are my findings:

Cold Engine Running
Block 2 - 39 to 42
Block 9 - 115
Fuel Temp - 98*F (37*C)

Warm Engine Running
Block 2 - 36 to 40
Block 9 - 185
Fuel Temp - 145*F (63*C)

Please don't jump on me for the Block 2 reading. I already know it's low. I had set it to 52 a few weeks ago. So this reading was a bit of a surprise. I suspect swapping in the stock injectors might have affected this. FWIW, 39 is still right in the middle of the graph given my Block 9 reading.

I'm thinking about jumping straight to the fuel temp sensor. But I've noticed two other things. First, that pesky N109 fault was listed again. I had hoped I was rid of that issue when I was chasing my alternator woes. There was no limp mode. LugNut felt the N109 fault was a result of something OTHER than N109. I have the part; so I may still replace it. But then there's the more curious issue... the "Bouncing Block 2." My Block 2 readings bounce quite a bit. Someone told me this is a sign of fuel "leaking" past the quantity adjuster. I couldn't find any reading to back this up. Can any experts comment on this?

Thanks,

Scott

Oh, outside temp was 90-degrees. I'll add that to the post above...

Jason,

compu_85 said:

Does you car shudder with the stock software? I see that it shudders with the UPS as well so that would tend to rule out the RC...

Click to expand...

While the RC3 software had me wondering last year, it was clear to me by April that the software is not at fault. I do not know if I have a slow-down shudder on stock software. I suppose I can try it out. But it'll have to wait since I'll be away from my toolbox for a while.

Scott

Although I checked the injector pop pressures twice and saw they were all the same, I suspected there might have been either a nozzle mismatch or something internal to the injector.

Click to expand...

Have you confirmed that the flows are equal? Think about what could happen with one .184 and three .205 nozzles.
"Pop" pressure, or cracking pressure is the amount of pressure required to open the nozzles, but what if one of the five ports were plugged or restricted? The initial pressure requirement is dependent on the shim preload. The flow rate is dependent on the tip orifice size. Light load would permit the requisite volume of idle speed fuel to pass within correct time duration if less than five orifices were open.
High load operation and the greater fuel volume delivery (in a shorter time span at higher rpm) might make the pressure rise significantly above the "pop" pressure and push fuel around a restriction.
Moderate load and lower rpm may allow one restricted injector take longer to squirt its charge of fuel (or a "lazy" one to inject more quickly) than the other three.
I had a moderate shudder, almost a mis-fire, with the 220 bar, .205 tip combination I had used for a long time. I learned to avoid the conditions that made the shudder. The operating range in which it occurred was narrow enough that it was more easily avoided than yours.
I had the .205 tips transferred to a set of 190 bar bodies and used a set of borrowed 220 bar, .184 tip injectors while the work was performed. Absolutely zero issues with the 220, .184 combination..
except the power.
I now have the 190 bar bodies reshimmed and with the .205 tips. Shudder is eliminated and that wonderful thrust has returned.

Jon,

Thanks for your input. However, I'm already using a set of stock injectors while troubleshooting this issue. So I can no longer blame the injectors for my problem. My plan of attack is to replace:

1) Thermostatic "T" above the fuel filter. I read another thread where that could contribute to high fuel temps if gone bad. I mentioned earlier in the thread that the shuddering wasn't so much of a problem during the winter (if any... I cannot remember). Anyway, I suppose my high fuel temps could be retarding the car to the point of causing an issue.

2) Fuel Temp Sensor. If the "T" doesn't bring my measured fuel temps down, then I'll see if the temp sensor does the trick. I'm still hung up on the fact that my measured fuel temp was only 8-degrees over ambient temp on a cold engine that had been running for just 1-minute. However, fuel temps shot to 145*F after just 20-minutes of driving.

4) Regardless of the outcome of #1 and #2, I'm going to readjust the injection timing back to about 52 in block #2.

5) My last resort is to replace the fuel pump. I wish I could get a solid answer regarding my bouncing block #2 above. Nevertheless, my fuel pump has 207,000-miles on it and my timing belt job is coming up. It can't hurt to replace it (although it would suck if my symptoms remained the same).

BTW, is there any chance a compression issue could be to blame? Or would a compression leak have a broader effect on driving?

Thanks,

Scott

PS: Steve, thanks for your PM. I'll keep it as a guide as I continue to troubleshoot.

Here's my post on eliminating my "shudder" with a similar setup as yours.

http://http://forums.tdiclub.com/showthread.php?t=127959

I thought I'd update this page as the mystery continues.

I replaced the injection pump when I replaced the timing belt last fall. The new IP took care of the slow-down shudder, but not the highway shudder. I already knew the case pressure valve was going south. Jeff suspected it was the cause of the shuddering. I hated the idea of returning an IP that works (although old). I was fortunate to find a junked AHU sitting outside in a junkyard. It's a big hunk of rust. I managed to get the IP for $200. I swapped the case pressure valves and returned the junked IP for my $600 core charge. Unfortunately, the highway shudder continued. In short, I paid $200 to have a decent spare IP on hand.

I'm not sure why I didn't think of this earlier, but I was messing around with the RC2/3 switchable files on my ECU. I discovered that RC3 had no shudder at all. Apparently, the ECU has two codings, one for automatic transmissions and another for manual transmissions. RC3 was loaded into the "automatic maps." Seeing the car drove fine on RC3 with the exception of an annoying "RPM hang" inherent to the "automatic" coding, I asked Jeff to flash me another chip with RC3 loaded into both codings. I drove RC3 on the manual code and still got the shudder! However, driving the exact same program in the automatic code resulted in a nearly flawless drive.

It became apparent to me that something was wrong with the ECU since the car's performance and manners are excellent with the correct ECU setting. I managed to find a new-in-the-box ECU for an excellent price. It's been COLD. So I wasn't willing to play with ECU swaps until recently. I anxiously swapped the ECUs. The problem still persists! Well, at least I have a spare ECU for a rainy day.

At this point, I'm completely baffled as to why the car would drive perfectly with RC3 loaded into the automatic code but drive horribly on the manual coding. The only thing I haven't done is tried the stock program. But I'm certain the stock files will work fine since the issue worsens as fuel delivery increases (does not matter if this is via software or nozzles). From here until the wheels fall off, I'm driving the car in the automatic coding unless someone can deliver an explanation and/or solution. The "annoying RPM hang" I mention above is fine now that I'm used to it. In fact, it comes in handy in competitive environments. The only other "glitch" is I cannot deactivate cruise control by depressing the clutch pedal since the automatic maps do not monitor the clutch pedal. Learning to use the switch instead was not a hard habit to develop.

I look forward to any explanations that might be out there. Thanks for reading the details and offering support.

Take Care,

Scott

I find it odd that it goes away on the automatic coding, and is present on the manual coding....interesting.

How are your nozzles/injectors? When have they last been pop tested?

How about IQ setting? I had the "automatic coding hang" between shifts but adjusting the IQ got rid of that.

What rpm does the shudder occur? Or is it all the time?

Alligator and co. claim to eliminate shudder on the A3. However, this would be an expensive test of a claim. Maybe they would be willing to offer a money-back guarantee by trying their program on the sole auspices of eliminating the shudder.

FWIW, my former Passat also shuddered. Having tried chips from 3 different vendors, some better than others, the two constants I found in my case were that:
1) shudder was worse with larger injectors (first stock, than OEM 110 HP units then OEM 150HP T4, and note that all my injectors were purchased complete and brand new, not new nozzles over old bodies, so injector balance was not an issue);
2) shudder was worse with colder ambient temperatures.

When Quicksilver was sold, I put back the smaller 110 HP injectors and felt the shudder was reduced to a threshold of noticeability with the latest RC software that was in there, so I left it at that but never pursued anything further.

However, from DIESEL DAZZLER's experience with his wildly-modded pickup, it had 1Z/AHU engine with the corresponding Mk3 Jetta ECU (JB suffix). It shuddered like crazy with an 11mm pump and Race520 injectors. Replacing the engine harness and ECU to that from a 98 Beetle (MkIV generation with "BD" suffix), as well as replacing the solenoid section of the injection pump from a MkIV eliminated the shudder.

The extensive experience with various chiptuning programs and Gerry's example above leads me to believe it's a software issue, with no disrespect intended to any chip vendor.

I would give Alligator's software a try if they are convinced it eliminates the problem.

With my slightly smaller turbo and 95% of the mods i have on still/now , my last map/programing was very good and i had no shudders what so ever.....it was pretty clean to say i had miner air leaks plus falling boost pressure....a good puff after gear changes.

So i would agree that its definitely a software problem and can be near as dam it eradicated.....

Scott,
Look for a package to arrive in the mail today or tomorrow...

Let me know if it helps...

Hi,

Thanks for your input. The injectors were checked last Fall. However, I feel I've ruled out the injectors by borrowing a set from Paramedick. They had about 3000-miles on them. Driving characteristics of the shudder are described in the OP.

I am open to trying out another program. But I'll not hold my breath for miracles. The car is operating far outside its intended purpose. So I accept that I may be doomed to drive on the automatic maps. Should I sell the car some day, I am extremely certain that returning the car to RC2 or less with smaller injectors will nearly eliminate the problem. Even with RC3 and B184s, the shudder is how TDIMeister describes: "a threshold of noticeability." Those who've owned A3s understand that behavior is almost normal... especially at 1600-rpm.

Charlie - Thanks for the package, an unsolicited act of support. I look forward to seeing it (I'm assuming it's a program and not another set of nozzles... either is okay with me ). Just to let you know, I only go to Newport News on the weekends. If I don't see the package tomorrow, then I will not be able to report results for about 10-days.

Thanks Again, Everyone!

Scott

Was the fuel temp sensor ever replaced? You didn't mention it was replaced.

Could be a cheap fix at $20-30.

Hi,

It was "replaced" by default when I installed the new IP. Oh, I forgot to mention that I removed the Epsilonian Device. It is no longer a suspect.

Scott

Charlie - Thanks for the package, an unsolicited act of support. I look forward to seeing it (I'm assuming it's a program and not another set of nozzles... either is okay with me ).

Click to expand...

If it's the Aligator "economy tune" then your problem will be solved...at least it solved my shudder after going round and round...now I can drive from idle on up in any gear at any throttle position and all I get is a smooth motor!

Charlie knows I drive my car in competitive events:


If "economy tune" equals "less fuel," I can get that from anyone, including RC or even UPs. Perhaps it's a different tuning that delivers plenty of fuel with different timing? Who knows? I look forward to seeing what's in store.

I think it is less aggressive with fueling at light throttle than others. Smooth...smooth...smooth!

Hi,

I used the Aligator tune for about two weeks. My unbiased report follows...

First, some definitions -

1) Rocketchip flashed the same RC3 file into both the automatic transmission ECU memory location (S001) and the manual transmission ECU memory location (S002). Switching between the two requires recoding the ECU between S001 and S002. I will refer to these files as RC3-001 and RC3-002.

2) Aligator programmed only the S002 location. I will refer to it as "Aligator." Duh!

3) I have an extra ECU. Therefore, the respective programs have been run continuously in their given ECU with no swapouts. I think it's safe to say both ECUs have "adapted" to their resident programs.

BACKGROUND

Ever since upgrading my fuel injectors, I've experienced a horrible shudder. I went back and forth between a "program problem" vs. "injector balance" vs. "bad IP" vs. "bad ECU." All of the hypotheses were sound and I blame no one for the expense and hassle of my troubleshooting endeavors, including what can be labeled as unnecessary purchases (ECU, IP). My decisions to replace certain items were based on the collective advise of many experts in this forum. No single person swayed me to make any regretable purchase decisions. In the end, I found the best drive quality with the RC3-001 program. No one knows why RC3-001 works and RC3-002 does not... they're the same program loaded into different ECU positions.

NOW, onto the evaluation.

I finally got my hands on the chipset Charlie sent me. As mentioned above, I certainly wasn't expecting any miracles. In fact, I installed the chip because it’s here and I felt like humoring the group. But I'm shocked to report that my extremely annoying highway shudder (shuddering to the point of being surprised I haven't damaged a motor mount...) is almost completely gone! I felt a bit of shudder just once at 72-mph on a small climb. I put it to the test on my weekly drive through the hills in MD. Shuddering does surface on occasion, but it’s VERY mild. The same trip would've driven me NUTS on the RC3-002... even UP2! I tried more testing at high speed with similar results. I was going to do some towing. But the weather did not cooperate. The only annoying shudder that remains is the "slow speed" or "low RPM" shudder. To my surprise, Aligator's tune is a step in the right direction. I'd have near-perfection if I had the Aligator highway manners along with stock-like neighborhood/traffic manners.

In short...

The good –

1) Shuddering appears to be nearly-solved... Not just good... GREAT! It still needs a little fine-tuning. But, overall, the shuddering is tolerable.

2) This is a 21.5-psi program. Therefore, power is comparable to RC3... perhaps a smidget less power...

3) Less smoke. But that MIGHT be at the expense of power. I'm still researching this. Third-gear 40-65-mph acceleration tests reveal negligible differences between the two. The differences are less than 1/10-second and can be attributed to my eye-hand coordination. As one would expect with "less smoke," EGTs at the top of each run are about 150-degrees lower than RC3-001... 1050* vs. 1200*. I'm not sure what difference a dyno will measure.

4) Good turbo control. There are no overshoots. But this is at the expense of spooling speed.

Needs improvement –

1) Slow-down shudder is still a problem... but it’s better than with UP2 and RC3-002. Cold engine shuddering is still present, too. But the car isn’t as grouchy as with RC3-002 on cold mornings.

2) Turbo spools slower... not later... just slower. This could be a good thing in some books since it eliminates overshoot and the chance of turbo surge. I do not tend to think the surging is as dangerous with the K03 as it is with the VNT-15. The slower spool also makes the program feel "less responsive." I just realized my IQ setting is a little more rich on the RC ECU than the Aligator ECU. Adjusting the Aligator ECU might "wake up" the spooling just a tad.

CONCLUSION

My problem is undoubtedly a software issue. I believe it can be resolved with patience and trial-error. Alligator may have found a magic program if he can get great "foot-down-pull" but with the light-go-pedal manners of the stock program. For now, RC3-001 still remains my smoothest program. I'm certain the Aligator file would be smooth if loaded into S001, too. I am anxious to see if either tuner can deliver a file that will run so smoothly in the S002 position.

In case you're wondering what the difference is between driving S001 and S002: S001 assumes an automatic transmission. Therefore, the revs do not drop immediately between shifts. The result is rough shifts until I became accustomed to a new driving style. The same sloppy shifts occurred when I returned to S002 for two weeks of testing since I had become accustomed to the different clutching method. Of potential safety concern is the fact that an S001 ECU ignores the clutch switch. This is not a big deal unless one expects the cruise control to disengage when the clutch is depressed. I've formed the habit of disengaging CC by either tapping the brake or turning CC off by the switch.

Well, I hope the info presented was worth the read.

Thanks for your input and continued support!

Scott

Hi Scott,

Shudder is cylinder pressure imbalance. This can be caused by nozzles, timing, and/or physical differences (ie, injector bodies, nozzles, compression, valve guides leaking, etc). I have driven many tuned A3's w/o the shudder you mention, including my own and never had this problem. Of course I rebuilt my motor w/ fresh head work and hard parts.

Maybe you are laboring the motor too much, I have ridden with many folks that roll into the throttle at 1500 and wonder why the motor lags so much. I didn't experience the shudder when I drove your car, but I do believe it would naturally get magnified as the tuning/fueling is increased (ie stage 3).

Slow down shudder can be attributed to rolling to a stop with the clutch out. VW engineers/documentation, suggest always depressing clutch when rolling to a stop. When the ecu sees the clutch switch (depressed) it switches over from active closed loop fueling control to fixed parameter open loop idle (timing/fuel/boost is fixed).

Since you replaced all the essentials (pump/ecu/injectors), I would say check the head and pistons next. It's simple to measure the piston to deck clearance, and conditions of the valves/guides. I always like to look at the cylinder head w/ gp's and injectors installed to see their protursion is symmetrical. That's how we noticed the incorrect nozzle washers way back when.

If you choose to race your car, it's a no brainer to pull the head every now and then to check things out. Heck we used to tear down our motors after every run or 2 in funnybike, no big deal.

Your car has a unique anomoly that few others also have. I'll look forward to future reports to find the real problem that apparently can't be fixed by software, unless fuel is removed.

Jeff

The Upsolute prog I had in the Grand Vitara caused a similar shudder/ pulse at highway speeds/ feathered throttle. Bl**dy annoying it was, too. Aligator's more subtle mapping cured it on the first attempt...

I'm not sure I agree with your assertion re. cylinder imbalance, Jeff. Smooth-running control is only active at idle, and this kind of "shudder" is very slow compared to the kind of "hunt" you get with an injector imbalance. In my experience, off- idle injector imbalances seem in the 4-5 Hz range, whereas the highway shudder is perhaps half that...

Aligator cleared up my shudder when switching chips from RC3...how is this not a programming issue then?

Either way I am happy with Aligator.

Scott, I'm glad to hear that you have made a great deal of progress to solve the shudder problem.

Jeff, I don't (fully) agree that hardware in the case of the A3/B4 is solely responsible for the shudder. It may contribute, but logically if the shudder can be drastically affected for better or for worse with nothing more than different programs, doesn't it stand to reason that the program has some kind of effect?

If the belief is that the injection pump is the culprit, I would like to draw attention again on DIESEL DAZZLER's truck, which I would consider as an
extreme case of the shuddering because of his mods. Replacing only the solenoid portion of the injection pump, while leaving the same pump lower end, and replacing the ECU to a `98 New Beetle one (originally an A3 Jetta unit), solved the shudder issue.

As for injectors and more specifically injector balance, I state again in my own case that I went through 2 sets of brand new, complete OEM injectors, not just new nozzles on old bodies. While one might argue that the injector balance on new parts themselves are subject to variance, the only consistent result was that shuddering got worse with bigger hole sizes.

As for labouring the engine causing the shudder, not at all. Those who drive A3/B4s with this shudder know that it occurs most noticeably at a level cruise almost exactly between 72-75 MPH in fifth-gear (corresponding too between 2400-2500 RPM on the tachometer) on a level cruise. The engine is (should be) by no means labouring in this condition.

IMHO the shuddering behavior is a peculiarity of the factory A3/B4 programming that is not normally touched by chiptuners' remapping, and seems to be simply exaggerated by remapping so by no means I fault the chiptuner, but give extra credit for anyone who finds the solution to it.

Hi Dave,

Changing archetecture from 68 pin to 80 pin is a huge improvement, imho. I see a new ecu, maf, map, throttle/pedel, QA, and n75 and vnt turbo in Gary's ride. That is not trivial change resulting in fixing shudder.

The A3/B4 maf calibration may be the hidden fix for the part throttle fueling/shudder. Don't ever forget that these engines are mass air flow control systems and can easily adjust to fueling mods (ie injectors/pump) without needing remapping.

When modifying the tuning file you typically adjust top end parameters (ie. drivers request, fuel, boost, and timing - above 50% throttle) with exception of what I call delta pedal or torque map. At steady state, on cruise all parameters are oem, until a small delta pedel is induced. The A3's are very slow in low/part throttle response compared to the A4's and I think this is mainly due to the maf response. If you give drivers request and have a slow responding sensor suite after fuel is given, the latter parameters like injection timing and boost may be slow to follow causing the fuel imbalance across all cylinders (opposed to cylinder to cylinder shudder).

I have since switched my A3 to vnt17 pp520 and A4 maf and it is much more responsive and no shudder - none. I drove it around on several trips to gtgs when I first rebuilt the motor with the oem turbo, sprint520's and RC3 and never had a hint of shudder. I also have oem exhaust. Next mods are thru exhaust, fmic, 11mm pump, and intank fuel pump. Maybe it's the way I drive (maybe not), but I'm not light on the throttle when I'm not on the cruise button, and I drive over 3-4k miles a month.

Jeff

Hi, Jeff,

Yes, I agree that something is definitely responsible in the A4 architecture to deal with this shudder that A3s exhibit, as yours and Gerry's examples show. Now then, the question is, what does Aligator do differently to his A3 program that gives the results that Scott experienced?