Okay guys, I have what I can best describe as an intermittent low idle. It seems to only happen when I have 1/4 tank of gas or less. Sometimes when I stop at a light my rpms will drop to 500 and lower, and it feels as if the car is going to stall, then, without pressing on the throttle at all, the idle will return to normal. Other than this, the car runs really strong. Any suggestions. By the way, I have already adjusted the IAC and TPS. Thanks for any info.

 

What mods do u have, pulleys or anything??


[This message has been edited by IROC-ZTWENTYGR8 (edited September 20, 2000).]

 

Mods are as follows...underdrive pulleys, headers (no AIR), catback exhaust, and all of the "free" mods.

 

check to see if you have an AMP drop when the idle goes low again. if so it is most likly due to the underdrive pulleys. had the same syptom when i installed mine. a higher then normal idle setting cured thid for me 650-700 rpm at idle, 900-1000 in park. if not the case i would recommend a AFPR and raise the fuel pressure slightly (46-48 PSI). or you might possibly have a fuel pump ready to **** the bed creating low line pressue and the ECM is increasing pulse with to the injectors to bring the idle back to baseline.

 

The pulleys have been on for over 2 years so that is not the problem. I've also connected a fuel pressure gauge, and it is fine (42 psi). I'll try bumping up the idle a bit and see if that helps. Any other suggestions?

 

Make sure your throttle plates in the throttle body (and the throttle body itself) are free from carbon build up. =

 

I had a very similar problem on mine. I would start it up or be sitting at a light and the rpm's would drop to lower than 500 and almost die then it would shoot up to idle if it had been running for a while but if I had just started it then it would shoot up to 1500 rpm. It ended up being my fuel filter.

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TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

Scotty D mentioned he adjusted his idle speed. How do you adjust idle rpm on a TPI? I would like to raise the idle on my car, but thought it was controlled by the computer.

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1988 GTA, 350; rebuilt, mostly stock; 700R4; rebuilt with Red Alto clutches and a Trans Go shift kit. Next mod ... Nitrous!

 

There's a torx headed screwon the drivers side of the throttle body, it may have a cap on it but I'm sure you can find it, once you do you shouldn't need to ask what to do next

 

You cannot change the idle speed on the TPI engines. You may only adjust the minimum air setting then the ECM will control the idle from there. Do not try to bump the idle up by simply adjusting the throttle screw you will confuse the ECM. I had a similar problem withan idle fluctuation and it turned out to be a faulty MAP sensor. I realize that you do not have a MAP on your vehicle but this shows that you do not want to start messing with the idle, let the ECM do it and just try to figure out what else could be giving the ECM bad info.
Two things you can easily check are the 02 sensor and the MAF sensor. The 02 can be visably checked for a white residue build-up on it that can cause the sensor to give the ECm info that it is rich and the ECM will cut back on the fuel unnecesarily, causing severe driability probs.
The MAF can be checked two ways. The first one is to disconnect the plug and see if the prob goes away, the other quick and dirty method is to rap on the outside of the MAF with a screwdriver and see if the idle quality changes, if so, it is possibly bad.

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"84Z28/'91 305TPI comp cam flowmaster TB coolant bypass/shutoff valve to heater core MAT relocated Ram-Air(home-made) gutted air-box IROC ground effects/wheels GY245/50's 700R4 superior shift kit/ corvette servo(excellent shift kit BTW) Rebuilt engine and transplanted it myself. Love this engine!
LOW performance people should drive low performance vehicles!