201-A4

Lets say I am cruising around in 4th or 5th gear and I mash the throttle at 2k, the motor will rev smoothly until 3k. When the motor reaches 3k, it lets out a popping noise once or twice, then stumbles up to 3400 rpm. After about 3500 everything is fine and the car pulls hard up to redline.

Last week I drove around with a trusted tech who was using a vag to check the specs, as the stumble occurred. He stated that the readings from the MAF, 02 and injectors all looked fine. I'm guessing he was monitoring blocks 002, 003, 031. There were no misfires and the knock sensors did not pick up on anything irregular. He diagnosed the popping as a backfire into the intake. He thought it could be caused by the throttle body malfunctioning in the 3000-3400 rev range. We did not get to try out a new throttle body because I had to go back to school.

I can not say for sure whether or not I had this problem pre-T28, but never the less it is very odd and I would like to correct it as soon as possible.

Has anyone had a problem similar to this?

Is his diagnosis accurate? If so, is the throttle body the culprit?

TIA

I made the same post in the Performance Forum but I didn't get much of a response.<ul><li><a href="https://forums.audiworld.com/performance/msgs/61256.phtml">X-post in the performace forum</a></li></ul>

RKA

it's getting dumped out of the cylinder, and into the cat?

201-A4

The pulgs looked fine.

RKA

Can you pull them and check the O rings?

Any chance the pop is mechanical in nature?

What plugs and gaps are you running?

Big Nodge

when I got my K04 installed i didn't know what pinging sounded like, on my car it was more like a clicking. the only reason I mention it is that it used to occur under similar circumstances to those you are describing with your issue, i.e. when boost comes on hard from low RPMs around 3k. If you have heard pinging before and can rule it out, then I am not sure. Hope that helps. My problem has gone away with the FMIC.

You could watch that video of digi racing the B6 S4 and listen to his car, it was pinging in the vid, and see if your issue sounds anything like that.

Yippers®

I'm with Raj . .IF you are running Denso Iridiums I'd start by switching them out.

RKA

It would have to be REALLY bad to sound like a *pop*.

201-A4

I hope that if it was pinging the tech would have picked it up. The car jerks when the pop occurs.

201-A4

While my car was there we tried a couple of differents sets of injectors, and there was no difference with any of them.

I had been running some copper pulgs @ 0.030" or 0.032". We switched to the denso's (Im not sure on the specs) and the engine is running smoother than ever, but its still got the same pop.

RKA

It's a relative cheap test. If it smooths out with the high octane, it's probably pinging.