Bad shaking getting worse - please help!

[riofrio]

A few weeks ago I started noticing what I thought was "shuddering": just some mild vibration at the gas pedal at certain rpms, barely noticeable otherwise.
Well, it's been getting progressively worse and just after 2 or 3 weeks it is getting to the point that it is very uncomfortable to be in the car (especially for passengers). I wouldn't call it "shuddering" anymore but rather "shaking". Here are some symptoms and pertaining info:

- It seems to happen only with light-to-medium throttle. It will go away if I either let go of the accelerator, or if I give it some boost.
- It does not seem to correlate to any specific wheel or engine speed. I'm fairly certain it is not drivetrain or wheel related, but rather engine or fuel delivery.
- It does not seem to be the "slow-down shudder" that people have mentioned in these forums: it simply goes away when I let go of the pedal.
- When I do give it boost, it pulls very nicely.... maybe not 100% but good enough.
- The IP is freshly rebuilt from DFIS, timing belt replaced less than 10K ago, and injection timing is slightly advanced (just under the top line).
- No smoke, even when I floor it. Car's got 320K miles on it and I believe the injectors and nozzles are still original stock.
- Oh yeah, my idle has been getting rougher in the exact same time frame.
- No CEL, no engine codes (well, other than the 01117).

I suspect (even though without fully understanding why) that this shaking might be related to badly toasted nozzles or worn injector(s). I'm getting a rebuilt set of injectors with Sprint 520 nozzles from Frank's VW TDI's, but he is on back order and it will be a couple of weeks.

But if it was related to nozzles or injectors, wouldn't I be seeing a lot of smoke? If anybody has seen something similar, or have some suggestions or questions, please chime in...

 

[thebigarniedog]

Do you have the same condition when reving the vehicle in neutral? How are your motor mounts looking?

 

[riofrio]

Good question. In neutral it is actually very difficult to reproduce it. the front motor mount was replaced recently, but I haven't inspected the other ones. What is the best way to check them?

 

[thebigarniedog]

Good question. In neutral it is actually very difficult to reproduce it. the front motor mount was replaced recently, but I haven't inspected the other ones. What is the best way to check them?

Here are the best links I can find. Sorry, I don't own a Passat:

http://www.myturbodiesel.com/1000q/a3b4/mk3-jetta-passat-motor-mount-replacement.htm

http://65.110.12.166/showthread.php?t=204605

 

[riofrio]

Thanks! I guess it would make sense to look at the mounts, considering the mileage. I guess that might explain why it only happens with light throttle and then go away with full throttle if that causes the whole engine to kick back.

 

[riofrio]

Yeah, other than a slightly rough idle it really doesn't shake when in neutral. So if this were a bad mount would I be looking at the transmission mount primarily? Any good way to inspect these mounts before spending the time and money barking up a wrong tree??

 

[thebigarniedog]

Yeah, other than a slightly rough idle it really doesn't shake when in neutral. So if this were a bad mount would I be looking at the transmission mount primarily? Any good way to inspect these mounts before spending the time and money barking up a wrong tree??

To be candid (while not a fan of blindly replacing stuff to see if it fixes a problem), your car is going on 15 model years old, so I would just replace all of the mounts.

 

[riofrio]

Question: What would be the difference in symptoms between bad shuddering (i.e., from an injector imbalance) and vibration caused by something mechanical (i.e., bad mounts)?
I'm ruling out wheel / axle issues based on the fact that I don't feel any of this on the steering wheel.

 

[TonyJetta]

Do you have VCDS? If so, you can look at the injector balance to rule out that issue.

I had a shudder when I first got the Passat going, but it was on take-off from a stop. Replacing all 3 mounts fixed it. This was with 139k on the car.

How many miles since the mounts were replaced on yours?

Tony

 

[riofrio]

Thanks Tony. Yes, I have VCDS... how do I check the injectors balance?

I have no idea when the mounts were replaced last. I bought the car at 233k and have put in almost 100k since. The front mount was recently replaced but no clue about the other 2. Could be the original ones for all I know! I will replace them soon, but I think it will take me some time to find someone that can do it for a reasonable price. From what I've heard, I'd rather not tinker with the transmission mount and have someone else do it. Some local shop quoted me $900 for all 3, I bet I could get it done for at least half that.

 

[TonyJetta]

There's all sorts of tdi gurus all along the east coast. IIRC, there is a guru locater website.

You should be able to find it easy enough. The measuring block you are looking for, has all 4 blocks indicating IQ.

I can run VCDS on my Passat, if you need specifics.

Tony

 

[riofrio]

Great, thanks. For some reason I thought only the 3rd injector IQ could be measured, and the computer would "assume" perfect balance. I'll check tomorrow and post my findings.

The closest Guru in my area is Meganuke, who is top notch. I haven't been able to get a hold of him recently so I'm just trying to cover my bases.

 

[riofrio]

Ok, I got some values on the injector balance, but I'm not sure how to interpret them.

Here's what I got:

At cold idle: cyl 1 (-1.08), cyl 2 (-1.84), cyl 3 (-1.65)

At highway speeds (avg): cyl 1 (-0.99), cyl 2 (-1.22), cyl 3 (-0.94)

At warm idle: cyl 1 (-3.01), cyl 2 (-2.96), cyl 3 (-0.16)

I've only checked these once, so I'm not sure how repeatable they are. What do the numbers mean? I assume some sort of IQ differential between adjacent injectors? Or are they all compared to injector 4?

 

[dieseldorf]

At warm idle: cyl 1 (-3.01), cyl 2 (-2.96), cyl 3 (-0.16)

It's the amount of correction the ECU assumes is needed to attain a smooth idle. You don't really want to see values in excess of +/- 2.0

You've got two values out of range, but I would not automatically assume that's the heart of your problem, but you may want to consider freshening up these nozzles at some point in the near future. We see cars with recent (and pop tested) nozzles coming in close to 0 across the range. Here's my car, for example:

 

[TonyJetta]

What dieseldorf said!

Looks like you are a candidate for new injector nozzles. I would talk to either member Franko6 or drivbiwire. Both offer excellent service.

Tony

 

[riofrio]

Thanks! Yes, I have a set of balanced injectors with Bosio Sprint 205 nozzles coming my way from Frank06 soon via his IG program. I guess I just need to wait and see what that does.
How come Dieseldorf's VCDS readings show a value for injector #4 and mine does not? I don't get a number in that cell at all, it's just blank.

 

[dieseldorf]

How come Dieseldorf's VCDS readings show a value for injector #4 and mine does not? I don't get a number in that cell at all, it's just blank.

The earliest cars only show three values as they reference the 4th cylinder.

 

[riofrio]

New injectors, shaking WORSE

Well, I finally was able to install a set of rebuilt injectors with new Bosio sprints. A fellow forum member helped out and provided his injector pop tester, so I was able to test all the old as well as the new (rebuilt) injectors. Here are the measured values:

Old Injectors:
#1 2300 psi
#2 2250 psi
#3 2400 psi
#4 2400 psi

They all tested low, but somewhat consistent.

Rebuilt injectors (right out of the box, and they came with the new nozzles installed):
#1 2800 psi
#2 3250 psi
#3 3450 psi
#4 3250 psi

Numbers seem inconsistent, but I went ahead and installed them anyway, and the shaking is much worse. It shakes at almost all speeds in all gears. I can get the shaking to stop if I stomp on the throttle and slowly ease off of it, but even doing this does not always work anymore. The idle is rough (it pulsates, and makes the whole engine shake). If I increase the rpms at idle, shaking goes away. I checked the injector balance with vag com and I get (-1.5),(-3),(-3). Clearly all out of spec. Adjusting the IQ is almost impossible due to the rough idle (numbers fluctuate all over the place), but if I rev it up to about 950 rpm, the IQ is listed high, between 5 and 6, and my adaptation number is maxed out at 132.

Anyone with injector pop testing experience can tell me whether these numbers are conclusive evidence of bad injectors, or are they still within spec? Is there anything other than injector pop pressures that influence Vag-Com's injector balance numbers?

Very frustated....

 

[KLXD]

These injectors have a two stage opening. You can't really see that with a conventional tester although I would think the results you get would be consistent. Hopefully on the injector guys will respond.

 

[riofrio]

Yup. I just spoke with Frank and he'll let me mail them back to him for an inspection. I'll post with updates.

I'm also wondering if there is any chance that my freshly-rebuilt IP from DFIS may have a slightly off-spec IQ housing, being that VCDS is reading a fairly high IQ with the adaptation number maxed out. Wondering if I should hammer mod it just to see if that regulates the idle.

 

[riofrio]

Problem persists

Okay, I just got the injectors re-balanced and re-installed (with brand new Sprint 520 nozzles). 1st stage pop pressures were consistent. Idle is still very rough and car still shakes with low-to-mid throttle. Timing is slightly advanced but well within spec. Injector Pump was rebuilt by DFIS less than 10k miles ago.

Here is the more interesting fact, which I think may be key in solving this issue: The injector balance on VCDS (measuring block 13) still shows numbers out of spec (inj 2 and 3 both show -3 mg/strk), and I know the injectors and the nozzles have been carefully calibrated. So what I'd like to know is, how does the ECU measure these values? what other factors / components other than the injection pump, injectors and nozzles contribute to good readings in this measuring block?? If someone has a good answer to this it would be much appreciated.

 

[TonyJetta]

What is the IQ, now?

Tony

 

[riofrio]

Tony, the IQ is hard to measure because at idle it fluctuates all over the place. If I gently step on the gas pedal and raise it to about 1000 rpms, the engine stabilizes and I get an IQ of about 6.0. My adaptation value is maxed out at 132, so I can't lower the IQ any further. The fact that this is a recent DFIS-rebuilt pump makes me hesitant about doing the hammer mod... what do you think?

 

[TonyJetta]

Reset the adaptation back to what it was before, and use the hammer mod to adjust the IQ.

The fact that it's bouncing around concerns me. Any idea if the crank timing pulley is solid, or loose?

Tony

 

[riofrio]

I'm very tempted to do the hammer mod, but I'm afraid it would void the warranty on a freshly-rebuilt pump from DFIS. But most of all, I'm skeptical that a newly rebuilt pump would be out of adjustment. Is it conceivable that QA adjustments are car-specific to the point that it could easily be out of adjustment right out of DFIS??

Meganuke did my timing belt last and I believe he used a torque wrench for everything. More recently, when cleaning my intake, I had to turn the engine by hand via the crank pulley and it felt very solid (and I only turned clock-wise). I should mention, however, that I have the infamous "chirp" on cold starts coming presumably from the timing belt tensioner, and I also know that my serpentine tensioner is not the correct one for my car, and it in fact is over-tensioning it. I wouldn't consider any of these to have anything to do with my problem, but maybe I'm wrong....

 

[TonyJetta]

Call DFIS, if you are unsure.

Have you confirmed the crank pulley is solid?

Tony

 

[riofrio]

Good call. I just talked to Mark at DFIS and he gave me green light to hammer mod. He thinks this is most likely my problem, too. I'll do this later this week when I get a chance and post results. I'll double-check that crank pulley, too. Thanks for your help!

 

[KLXD]

The injector balance is the ECU's attempt to hold idle steady. It is injecting less fuel for 2 and 3 than 4 and the same as 4 for 1.

Other than poor injector balance, this can be caused by different compression, bad cam or valves, etc. Anything that can cause one cylinder to run better or worse than the reference cylinder. The ECU uses the displacement sensor in the QA to determine IQ.

 

[riofrio]

Update...

I did the hammer mod yesterday. I still can't get the IQ to stabilize, even though it's in the right range (if I gently apply some throttle and raise the idle to 950 rpm, it stabilizes with an IQ of 4.0). I'm ruling out IQ adjustment at this point.

My two main suspects right now are the ECU and the IP. Is it unheard-of that a rebuilt IP from DFIS may be bad?

 

[rdkern]

Did you check the crank pulley as was previously suggested?