Ok My car just started this 3 days ago and it runs like complete crap and i have done everything to fix it and nothing has worked...and i need her cuz she is my everyday driver.....This is my Problem.....As soon as she warms up for a min or 2 the idle goes to all hell.....It will sit right about 650 then it starts to sound like its missin real bad and it will drop below 500 and sound like its about to stall out and the computer corrects it and sends the revs back up to about 1k and it idles back to 650 and repeats its self...it does this while driving too...u can be goin 35 steady and it start to miss bad, rpms drop way down and then shoot way back up to where they were...and it will do it non stop constantly.....Now if it starts doing this and u floor it....it takes off like a bat outta hell...it will not have this problem if u put it under a heavy load.....

Im not getting an SES light....i have changed the following.....New cap,rotor,plugs,wires,coil, Module, distributor, Yes the timing is right and i unplugged the ESt when i did it...the gap on the plugs are correct also....Replaced IAC,MAP,TPS, Fuel filter, EGR,CTS...basically most the sensors and a fulll tune up....and it has not fixed this....i did find a very tiny vaccum leak and replaced the hose but it did not fix my problem......I have been thinkin fuel pump but it does make sense that it runs sweet when its under full throttle....someone please chime in

 

vacuum leak?

 

ive looked everywhere cant find one....cant hear one and ive sprayed the engine bay down with brake clean and nothin.....im just at a loss here...im desperate

 

what about the fuel pressure regulator

 

Fuel pressure is where I'd start. Maybe the initial prime gets her going but the pressure drops later on. Maybe the pump isn't steady or worn. If that isn't it...

1-2 minutes isn't enough to get the O2 sensor warmed up and working, so your still in open loop, so CTS/O2 sensor isn't in the equation yet. But you say fully warmed up it happens too so...

MAF or MAP? If MAP suspect a vacuum leak first. If MAF, pull the MAF cable off to force it into open loop so CTS/O2 sensor are definitely out of the picture, then look for a vacuum leak.

Stuck or leaking EGR can do this, stuck or dirty PCV valve too.

I'd say dirty IAC pintle, clogged IAC passages/plenum but if it happens at fully warmed up low speed IAC isn't the problem.

Partially clogged injectors might not meter correctly at slower fuel delivery (as opposed to faster delivery when you stomp on it).