my car doesn't know how to IDLE!!!!! HELP!

[mitsubluetalon]

hey guys, what reason would there be for my car to run totally normal when you first start it up, but then a minute later, starting to sputter until it develops to to the point where the engine barely runs. with the idle between 500-700rpm.

but it runs normal on initial startup. up to 1500, and then a minute later brrrrrrrrrrUPrrrrrrrrrrrrrrrrrUPrrrrrUPrrrrrrrrrrrrrUPrrrUPrrrUPrrrUPrUP......until it develops into a total sputtering, barely running engine. if i hit the throttle, it will almost stall for a second. then rpms go up and no sputtering, but then back down, sounds normal for a second, then back to sputttering......anybody have a clue?

i have done a boost leak test, and i have some small leaks out of my injector seals and probably some other places, so i have to fix those. but i'm skeptical that this is what is making my car idle and run so bad.

i was thinking that it could be my O2 sensor, as i've heard rumours that if your O2 sensor was faulty, it actually could throw a different code. i've had a code come up before come up and it was for the throttle position sensor but with the voltmeter i've determined that the TPS works just fine.

DOES anybody have any thoughts???

 

[ddavisaf]

Could quite possibly be your tps, isc, o2 sensor, spark plugs, wires.... MAF, bunch of things. First thing first, you found a boost leak so fix that. Check your plugs, make sure they're gapped and they're not platinum's. After you do that then we'll start getting more technical.

 

[mitsubluetalon]

well i checked my wires but they are new, checked my plugs, buy they are good, umm they are also irridium, i'm not sure if that matters. but whats wrong with platinum plugs? i've never had any trouble with them before. i've now determined that its my injectors that shut off. i put a screw driver tip on each injector, and each one ticks, but when i slowly rev the engine up to 1500, i can hear that its the injectors that shut off, until the rpms drop to 1000. then they kick in again,

so i'm tracing up the line, the injectors are good, and so is the harness, the ecu is from a galant VR-4, and has been socketed, re-mapped, and chipped with a stage 2 chip. so right there i'm thinking that this ECU is not compatible with my engine. the guy i bought it from said it was.

as of now i do have a boost leak, but its not the cause of this engine malfunction. The ECU is questionable, My O2 sensor has not been replaced and i am not sure how to test it, but i will do some research on how. i'm thinking its either a sensor malfunction, that hasn't thrown a code, or the ECU is the culprit. any takers?

Jason.

 

[VBGSX]

How do you know the vacuum leak isn't your problem?
A vacuum leak can cause the bad idle, to the point of stalling.
Like someone else said, eliminate that as your problem.
Plus is will allow your car to run better anyway.

Once that's eliminated, we can go from there

 

[mitsubluetalon]

i understand that, but would a boost leak, (that i've probably had before these problems) cause my injectors to shut off at an exact rpm, and turn back on at an exact rpm? seems more to do with a fuel mapping problem with my new ECU that might have compatibility problems. but nevertheless, i will be ripping my head appart here pretty soon, i've ordered one from the states that has been rebuilt so i will be going with all new gaskets everywhere. thank you for the reply.

the head that is on my car right now is borrowed from a friends engine that he did an engine swap on. but i put on a brand new head gasket naturally. now this head gasket has only been on the car for about a week and its never been driven. only idled. my question is when i put on my new head in a couple weeks do i absolutely need to put on another new head gasket or can i use this one.

thank you all for your support and knowledge.

Jason

 

[Kevd629]

I had a problem almost like that only my car would stall if i took my foot of the gas. It turned out to be a bad MAP sensor and a slight leak in my upper intercooler pipe.

 

[mitsubluetalon]

PROBLEM SOLVED as it turns out, my suspisions were correct. it was the performance ECU that made my car run like crap. for some reason every time i let off the throttle to stop acclerating, my injectors would shut off until you either open the throttle or until rpms drop to 1000.

my BISS was also to blame for the high idle osscillations reving between 1300-1500 rpm's. i cleaned the screw, put a new ring on it and reset the idle to 750. and it runs like a dream.

I would just like to thank everyone for sharring their past experiences and knowledge. my car would not be running if it weren't for you guys!!

thank you.

Jason.