all my mods are ported maf ends, ported tb, smoothe bellow, slp lid, slp lm2 catback.

first off i'll tell you about my problem:
for a while now my car has been wanting to speed up on its own(like when i'm pulling out of my driveway the car it will be fine for a few seconds but then it will go from the normal idleing speed to about 900 rpm all on its own making me have to brake) then when pulling up to a stop sign or stop light the car will hold an idle at about 750 or 800 for a few seconds then go back to the normal speed.

i can put the car in neutral going down the road at say 35mph and the rpm will speed up to about 1700 rpm and slowly slow down as the car slows down(i'm know sure if this is normal but i would imagine this isn't the case for most A4 cars out there.)

also the car does not want to slow down when letting off the gas, lets say i'm going down the street at 30mph: the car will just stay at that speed holding a constant 1000rpms until i go up a hill then it will slow down slowly, but when going downhill it speeds up way too much. but when i am at higher speeds like 55-60mph the car will slow down at the normal rate and no problem.

well i thought my problem might have been porting the maf so i swapped mine for a stock one but still the same problem, then i thought it might have been my p&p throttle body but i swapped it out for a stock one as well but no change, then i bought a new iac motor but it didn't help as well. i even took it to a shop and pay $300 for them to reflash my computer and put a new pcv hose and check for a vacuum leak but they found nothing.. i haven't done any tuning to the car because i haven't done any performance upgrades that would need it.. i'm all out of things i can think of that would be causing it to do this.. . i'm not that knowledgeable about my car so i figured someone on here might know what's causing this problem or someone else that's had this problem could chime in on what it was..

 

having the same problem and noone knows how to help. i also did an TB upgrade and thought that was it and the maf replaced both and still have the same problem. and tps's someone told me to drill the ends and turn it but that has not helped either i'm lost as well. i'm going to get it dynoed this week. if i figure it out i will let u know asap.

it's very frustrating

 

This was happening on my Formula, and no one could figure it out. It had SLP LID, Bellow, MAF, LM, Kooks w/ catted y. I had 3 different shops tune it, looked all over for vacumn leaks, NEVER found out why, and never will thanks to Hurricane Dike.

 

yea it is getting very frustrating, let me know if you guys get if figured out and thanks.

 

damn i have similar issues on my 98 m6 ls1 in my 240

I have a 98 ls1 in my s13. It was running great for about 2.5 years. Then randomly on the freeway the engine would just cut out and turn back on. I ignorned that for the most part. Then i started to notice when i would start the car somtimes it would sound like it would start only on a few cyln or start with wrong firing then smooth out after like 1 second and drive perfectly fine. Lately i have been driving and it will randomly hesitate out of no where for a milisec. long enough to feel a jerk in the engine. Then when i come to stop light it will be idling around 800 and out of no where rev up to 1500 to 2000 rpm and drop down a couple times.

I have done many searches and have found people with the idle issues but no fixes but i think this is somthing that has to possibly do with my cam angle sensor and crank angle sensor. I would wrather change the sensor next to the starter before pulling the intake. I have thought about a clogged vette fuel filter or bad fuel pump but It seems as if it a firing issue. I have new plugs and msd wire. I have some extra coilpacks but i doubt thats it.

I have run the scanner on it and only codes i got was that i dont have a ces light hooked up. I have yet to hook it up on my friend snap on scanner to do some test. If anyone has any ideas please let me know. Also i have gone through the wiring and its perfect no issues.

thanks in advance.

 

This same sort of thing happened to my buddies 00 ss when he pulled the vacuum hose off of his stock tb and it only stopped once he got the hole in the top of the tb fully sealed up correctly. I think it's a vacuum leak guys, even though they have already been looked at for that, may want to get it checked again. It could be something else, but that was what was wrong with his.

 

well i finally figured out the problem just a second ago, i pulled the a/c and cruise fuse in the fuse box and the car seems to be back to normal, i never use the a/c anyways except when its 100 degrees out here in the summer

 

I just fixed the problem. I change my water temp sensor and it gave me a code, change to a new temp sensor still the code. Still shitty weird random idle. Then i took connector on harness and use a pick and tightend up the female ends inside and used dialectic grease and pluged it in. Cleared codes and drove it 60 miles and no issues with it cutting out or the weird reving at stop lights anymore. No codes but code 650 that means i have no MIL hooked up. I hope this may solve somone elses issues.