jasons88gta

I have a 2002 trans am ws6 with 49k. The car has long tube headers with cats slp loudmouth catback slp lid slp maf and 90mm throttle body. It has a very rough idle and shakes sometimes so bad the car cut off. The car is running very rich and im getting horrible fuel milage. i have no check engine light, i have replace plugs and wires the fuel pump/ filter new intake gasket new tps new iac new thermostat and new coolant temp sensor have tested the fuel pressure 58psi not sure what else to do the car runs good when going down the road but when u come to a stop and push in the clucth the car drops to about 500rpm then comes back to about 900. Ive been putting seafoam in it for the last 5 or 6 fill ups and nothing. I was thinking it might be a vaccum leak anybody have any ideas?

TheSilverOne

iTrader: (22)

replace the slp maf with a stock one

poltergeist 02

iTrader: (65)

test your throttle position sensor voltage. if i remember right, it should be around .57v at idle/throttle closed. also make sure that you are at 0% throttle position. you will need access to a scan tool to look at these numbers. once you get it to .57v with the throttle closed you will want to do a tps relearn. this is how: unplug the tps with the key in the off position, now with the sensor still unplugged turn the key to the on position for a few seconds but do not start the car, turn the key back to the off position and plug the sensor back in, now start the car. tps should now read 0% throttle position at idle. this may be an issue with your car but it may also be a vacuum leak as you stated.

jasons88gta

My Tps is showing 3.1% to 3.5% on my scan tool I tried the relearn but it wouldn't reset it back to zero.

TImmy_Jones

iTrader: (4)

Stock MAF is good for 500 HP, get that and a ported stock throttle body!!

poltergeist 02

iTrader: (65)

thats a problem. should be 0% what is the voltage at?

jasons88gta

the voltage is .9 lol

jimmyblue

iTrader: (11)

Are your O2 sensors 10 years old?

jasons88gta

I know three of the o2s have been replaced not sure bout the fourth the scan tool shows all them working

jasons88gta

I think today I'm gonna put on the stock tb and maf and see if that will fix the Tps

tripblackls1

iTrader: (11)

A faulty map sensor will cause these problems as well

c0ncEpT

iTrader: (4)

Does your HVAC work? Check to see of the plastic vacuum line going into the back of the intake is broken.

poltergeist 02

iTrader: (65)

you need to adjust the set screw and get the voltage up to .57 then do a relearn. get that corrected first then move on if the car still doesn't run right.

01CaMMMaro

iTrader: (25)

Gonna ttt this, I'm having the same problem. Did the relearn and nothing. I have longtubes and the longer vette O2 sensors and my rears and tuned out. Car drove fine one day and bad idle the next. My car idles around 500 for about 5-10 seconds then picks back up to where it should be. Car drives fine other than the idle though. I have no cats and TSP true duals also. The O2 sensors are maybe 3 months old as well as the plugs and wires.

01CaMMMaro

iTrader: (25)

Noticed today that it also drops down then back up when I turn the A/C on.

NY02ws6

have you tried cleaning your IAC and TB?

01CaMMMaro

iTrader: (25)

No I haven't, today I also noticed that it only goes the rough idle sometimes... Sometimes it starts up fine and sometimes it doesn't.

Should I try some of the spray type sea foam to clean my IAC and TB?

disc0monkey

iTrader: (10)

vacuum leak?

thunderstruck507

iTrader: (18)

I have a friend whose car has done this for years.

We have looked at and tried just about everything. He replaced every rubber bit on the car looking for a vacuum leak. Maf, tps, and map are all fine. Pretty much given up on it.

disc0monkey

iTrader: (10)

can the pcm be fried? i know microprocessors can loose clock speed over time and or exposure to elements