I have never heard of anything like this happening before...

[jlien08]

To start off with, I have a '98.5 A4 1.8TQ Tip with 178,000 miles on her.

I warm my car up every morning for 10-15 minutes or more while I get my daughter ready in the morning. I've never had any engine issues in the cold, ever. Until now...

I went to leave this morning, and my car seems like it is bucking/RPM's are jumping without me even touching the pedal. I'm talking like 1000rpm up to ~2000rpm and then holding. It's like the ECU is giving the engine gas without me even touching the pedal. My brakes also seem like they are locked up. They are REALLY hard to push, and when coming to a stop, I'd have to use both feet just so the car didn't keep rolling (again, the car is still trying to move without me touching the gas pedal). While going down the street I live on, I hit 35mph without ever touching the gas pedal!!! I managed to get it back in the driveway and when I put it into park, it revved all the way up to 4000rpm and was holding it there. My tranny fluid was changed about 10,000 miles ago. The only thing I can come up with is the tranny, or tranny tcu... I have VAG-cam, but won't be able to use it until this evening.

WTF is my problem?!


edit: i also have an APR ecu in currently, I am going to switch it out with my stock ecu and see if that happens to change anything.

[mainer0311]

maybe a vacuum leak??

[Gibbs]

maybe a vacuum leak??

sounds like it. check all pipes mate i had one lose down by the inter cooler but the weirdness would only kick in between 2 and 3K revs

[Jibberific]

i used to have a 96 stratus that did the same thing, only intermittently. at red lights i would have to stand on the brakes to stop it from rolling into the car in front of me. never did figure it out....

[jlien08]

i used to have a 96 stratus that did the same thing, only intermittently. at red lights i would have to stand on the brakes to stop it from rolling into the car in front of me. never did figure it out....

Yeah that sounds like my problem... It's re-freakin-diculous. I'll check it out... I have replaced a majority of the lines in the last year.

also, what about the throttle body needing to be recalibrated? someone had mentioned that. Is that a possibility?

[Jibberific]

yes i think the throttle body was brought up in a previous thread someone else posted concerning this. having it stuck open might be what is making it hold a certain amount of revs and take off without the gas pedal being pressed.

[Spykce]

Sounds just like my girlfriends cabriolet. We haven't found the issue yet. Fairly certain it's vacuum related...

[jlien08]

On another forum someone mentioned that if it was a vacuum leak that large, there is no way it would continue to run while hitting 4000rpm with the MAF plugged in. I would have to agree with that. I'm going to try recalibrating the TB tonight and see if that helps. Thanks for all the input!!

[solowb5]

Never dabbled in autos that long but, I did build a fairly fast one once. Never had it happen but, maybe it might be the tq convertor?

[jlien08]

I sure hope not!

[onemoremile]

Just check anything that leads to the power brakes. Start there and work back.

[djwimbo]

Just check anything that leads to the power brakes. Start there and work back.

Exactly.

There should be a large boost/vacuum hose from the intake manifold to the brake booster (big black pancake looking thing next to the ECU box) on the bulkhead/firewall. It has a connection at the secondary bulkhead near the coolant reservoir. Check to make sure it's plugged into that grommet, and the line from that grommet to the booster is in tact.

I'm looking for a pic for reference...

[B5A4Kevin]

just as wimbo and onemore said, this is what i was thinking as i read your post. most likely a large vacuum leak (unplugged hose) to the vacuum assisted brake booster, causing unmetered air (erratic idle and drive characteristics), as well as excessive braking effort needed to stop. most likely an easy fix, but definetly get it handled soon.

[jlien08]

Again, thanks for the info guys.

It's parked in the garage for now... thank god I have a spare vehicle!

[jlien08]

ALRIGHT! Here is is:

Well, I'll start off by saying those of you thinking it was a vac leak were right.

BUT, it was one of those total flukes that will probably never ever happen again to anybody, ever. I came home and popped the hood. I did a once-over on the intake manifold, and low and behold, there was my problem. My IAT sensor somehow popped out of the intake manifold, and being that it was still connected, it was pulling readings that were, of course, majorly lean. The only thing I can come up with is that the bolt that holds it to the IM some how backed it's way out. It's nowhere to be seen. I don't really care how it happened, I'm just happy that all it will take to fix is a darn BOLT!!!

Again, thanks for all the help guys!

[djwimbo]

That'll do it.

Good job on the find.

[somebody5788]

definitely a big vacuum leak