Stealth TDI
Pre-Forum Veteran Member
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.
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.
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