[StanR]

When accelerating even slightly when the engine is under load I get a shudder with the frequency of being on a rumble strip at about 30 MPH. I can accelerate on through it. Usually it's just for a few seconds and it doesn't shake the car. More like a rapid misfire. I have battled this for several years and it has gone away for months at a time. I have tried engine treatments and have sometimes thought they helped but not sure.
I had to replace the ECU about 3 months ago and the shudder stopped for a couple months then came back. this may have just been a coincidence.
I am new to VCDS and, of course, this forum. If anyone can offer help for this problem it will be much appreciated.
Thanks

 

[udraft]

What engine? That's an odd one for a diesel. Changed ECU clears up temporarily makes me think something electric, but there ain't much electrics going on under acceleration. Failing DMF or motor mount?
Almost forgot to ask- What transmission? The 01M is famous for this type of stuff.
Check for stored codes.

 

[StanR]

Thanks for the reply. I'm new to the forum and I realize there is a lot of info I left out.
The engine is a MK4 ALH TDI with an automatic transmission. 217K on the odometer, and I have owned the car since 35K .
A motor mount has crossed my mind as a possibility. However, even though the shudder can be felt it seems to be isolated with the engine. I read somewhere the mounts are fluid filled and to look for leaks . I have but there is no evidence of leaks. also, since it has been going on for several years, it would seem that a mount would continue to deteriorate and the problem get worse.
I also had a limp mode problem at times for a few years. Nearly 2 years ago I replaced the MAF sensor and the air filter with OEM and cleared up the limp mode and for months I didn't have the shudder.
The turbo seems good. Using a vacuum pump the actuator works very precisely with no jerking or hanging. Vacuum lines are all good and I have switched the boost and EGR solenoids temporily and checked them thoroughly. With VCDS the actual boost and requested boost look good. I just timed the injection pump and still no change in the shudder. A few weeks ago I drove it on a 400 mile trip over a mountain and lots of hills with very little shudder. No check engine code is ever set. The MAF change, the ECU change and even fuel additives at times seemed to eliminate it for a while, but since it comes back it leaves some doubt.
I have done nothing to the injectors and I don't have any feel as to whether they could cause the problem. I have read several posts that sound like exactly the same problem, but nobody seems to have found a definite solution.
Again, I appreciate to thinking about this with me.