OK, it's a 95 Pontiac Trans Sport, 141,XXX miles on a 3.1L TBI V6 Auto 3 speed.

Whenever you start the motor cold, the RPM fluctuates by about 300 RPM and it will stumble and die unless you rev the motor a little bit to keep it running. If you let it die, it shoots codes: 32 (EGR Sys), 33 (MAP Sensor), 34 (Vacuum Sensor or MAP Sensor), & 45 (O2 Sensor indicates rich exhaust).

Also, when you put it in gear and keep the accelerator steady, it will run good for a sec, then stumble and bog for a sec (may or may not get a backfire through the throttle body), run good for a sec...etc. and keep doing that for about 10 seconds then it will run fine and stay that way till you turn the engine off and wait about 15 - 20 minutes and it will do it all over again.

Now, everything that I have done to it: New plugs, new cap and rotor, new feul injectors, new feul filter, new air filter, new PCV valve, new thermostat (cause it was overcooling), i took the EGR off and moved the piston then while depressed i covered the vacuum fitting and it holds vacuum so i figure its good and it is not clogged, swapped out the EGR vacuum control valve, swapped out the IAC valve, swapped out the TPS, bypassed the EST to check the base timing and it was supposed to be at 10 BTDC and found out it was set at 0 so i reset the timing to 10, getting ready to do the O2 sensor (there is only 1 at the exhaust manifold and not 1 behind the cat conv. like the book said).

Also, I noticed that the damper door inside the air cleaner assembly snorkel does move, shuts when cold and opens up while warming up. But while warming up, it will alternate opening and closing....is this normal, or could this be the problem?

I am at a real loss for what to do, any help would be appreciated greatly!!!


Blackhawk357m

 

is your IAC installed correctly>? ive seen them be just slightly out on the 2.8 and 3.1 and run like garbage