Engine RPM surging 100-200 rpms between 1000-2000 RPMS

[tewnick]

I have a 2001 A6 2.7t. under light acceleration I get a pulsation or surging in the RPMs between 1000-2000 RPMs.
Above 2000 RPMs and it smooths out.
Replaced the Gas cap, purge valve. Per mechanics recomendation, Just had the engine out and replaced the items that looked bad.
It was doing this with the last engine.

I have a vag com and will log what ever I need to.

Please let me know what i need to log that would help provide some guidance.

I do get a small evap leak off and on. I was told it was the fuel cap , replaced fuel cap and still comes back every so often.

[a4kamila6]

It would be good to check for obvious vacuum leaks. If you can, do a smoke test and a boost leak test. I'd say once your leaks are taken care of, you can go from there.


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[tewnick]

I tried to replace the obvious items already while engine was out of car. It also has new DVs, I will try to find someone close by with a smoke machine.

[A Stupid Turtle]

MAF sensor my guess.

[tewnick]

Smoke came pouring out the leak detection pump behind driver rear tire.

[a4kamila6]

Get'r done and hopefully thats a step towards the solution.


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[tewnick]

Got the Evap leak sorted. No change Still have bad surging. What should I log to narrow this down?

[S6XTC]

Torque converter can cause a rpm surge too... dont ask how I know...

[A Stupid Turtle]

The stall within a few s6's I hear make a dying MAF more pronounced and will induce surging is what I heard, and I experience..

[tewnick]

Thank you for the info.
Is there anyway to log to determine if my MAF is going bad? Or just unplug it an d go for a ride?


It is not throwing a MAF code(yet).

[tewnick]

I was told to press the brake while it is surging and if it stops then that is the Torque Converter. Still does it. I tried unplugging the MAF. Still no change?

Any ideas what to do next?

[JBX]

Try googling your car along with "coolant temperature sender" and see if any symptoms matches yours. I just installed this:

http://www.ebay.com/itm/351317372426...%3AMEBIDX%3AIT

I believe it will fit your car as well.

My symptoms differ from yours--mine were all cold/warm start related but cleaning the MAF, throttle body plate (don't touch or force the plate*), and replacing the coolant temp sender seems to have helped a lot. I just installed it on Monday and the S6 is one of 5 cars so I haven't had enough time to say it is completely fixed.

(*Clean the TB plate with it closed and open. To open it have an assistant or use a brick on the accel pedal. I was generous with cleaner when I cleaned mine.)

Hope it works for you.

--jb

[tewnick]

JBX thank you for the input.
A couple months ago I replace that same sensor for different reasons. No change.

Last month when I replaced my engine I swapped over my intake and cleaned the throttle body thoroughly.

It is looking like it might be the Torque Converter.
Really sucks since I was going to order a rebuilt one. Erickson industries talked me out of it and said they did not think I would need to replace it. Would of only cost me $300 to replace it when I replaced the engine. Now it will cost me $1,000.

I just wish there was a way to log it an confirm.

[JTown77]

Any update on this?