So I have this on going problem with my 1988 Firebird Formula. It has a 350 TPI engine in it. The current problem right now is no matter what, each time I start the car, it will rev up to at most 1,500 rpms then within a couple seconds work its way down to 900 rpms. However, after waiting for a minute, about enough time for me to take out my radio's faceplate and put it in, the car will idle down further. 500-600 rpms varying from each time. No matter what I do, it will continue to set itself there. Ive tried adjusting the screw that pushes the throttle forward to give it a higher idle, but it only goes right back down. There is no service engine soon light, maybe every once in a great while, but typically it never comes on.

Some other things that someone might need to know about: The car sometimes takes a while to start. It will turn and turn for a good length of time, then it will fire up. If the car has been sitting over night, it will run rough, idling up and down from 1,000 rpms to 500 rpms, sounding as if it is about to die out. A dealership told me that they looked into the computer module and apparently it says the engine is hotter than what it really is. The former owner did say the chip was customized, and so I guess the trick was to give the engine more gas by making it think its hotter. The engine is not the one it originally came with when I bought it, either. The original had a knocking noise in it, so I replaced the block with a used 350 from Everdrive. Just transferred everything over. The original was supposedly rebuilt, and bored out, had roller rockers, and some kind of camshaft upgrade. Any help to what I could do myself to find the problem here. (I am not all that great with cars yet)

 

Im no sure if the chip has anything to with it but my car goes to about 1200 rpms when started and drops to 500 when idling. as far as i am concerned this is normal. The engine I have is a carbed 305 which is all stock and runs strong. I find in my car that if I pump the gas 3 or 4 times the car starts easily. Try that and see if it starts right up

 

Since you don't know what has been done to the engine or the chip, it will be difficult to diagnose and fix.

You may have a faulty IAC (Idle Air Control) motor, as this is what the ECM uses to maintain the target Idle Speed that is programmed into the chip.
Target Idle is around 600rpm on an Auto in Park.

I am not sure what the Dealer is talking about when they said that the chip makes the computer think it is hotter than it is.

 

Damn Zepher just saw your video and you got some serious driving skill! Cant believe you only knocked down 1 cone! What engine are you running?

 

I don't know if the idle really should be set to 600 rpms for this car. When it idles down like described, I notice the battery charge goes down considerably, maybe about 10-11 volts. Also, the oil pressure is about 15 when the engine is warmed up enough. Once I give it gas, the volts go up to anywhere between 13-14 and the oil pressure 30-45, depending on how much im revving it up. Once it is running low like that, sometimes it runs rough, sounds like it could possibly stall if something pulled on it a little too much. If that really is all normal, let me know.

Ah, thats another thing.. I had my oil changed by Wal-Mart while I was at work. I knew it needed to be changed soon since I have a crack in my valve cover. (People who put in the replacement block tightened a bolt down too much) So over the course of 3,000 miles I lost a quart. But I noticed they put 5w20 in it. Should I be going with some other grade? like 10w-30/40? I personally have always put 10w30 in it.

 

Yeah, I put 10w30 with a quart of the lucas oil ( really does help ). also, the iddle is right. On my dad 88 formula tpi and my 86 firebird we both read around 500-700 rpms.

 

Thanks.
If you watched the video in my sig, I hit 2 cones.
Motor is a 305TPI with headers and stealthram with all the mods in my sig.

 

ok, so the car did something different yet again today. During my lunch today, I drove it to go out to eat, and it was running the same way as Ive explained. But when I came back, I put it in park and sat there to eat my lunch. After sitting there for a while, I noticed the engine began to rev up and down, a cycle of going from 500 to 700 back down, and 500 to 900.. it would do this repeatedly. I let it go for a few minutes and then it finally just stalled out of no where. Started it back up and it resumed the same thing, so I started to give it a little gas, revving it up to 1500 and I noticed it seemed to stick at those rpm's for a little too long, and then it would drop. Before I left work, I went ahead adjusted the screw to push the throttle foward until I got a solid response. The car revved up, and the idle was staying at 700 rpms. Got a check engine light on the way back, but only for a few minutes and then it went away. When I parked it, it was idling at 1,000 rpms. So maybe it is just a bad idle sensor? Or TPS not adjusted right? could it even be what the dealership says and that I need to replace the computer chip? If so, what should I get... Ive been looking at the Hypertech Thermoflo and getting their thermostat to go with it.

Also, one other dillema... my brother has asked me to take back the original engine he was holding on to for me. The original engine was taken out due to a knocking noise.. it had roller rockers, specially bored out, i dont know the specs on that one, i know some kind of camshaft upgrade (the owner was going for an LS1 conversion) and headers. My dillema would be, should I go ahead and try getting someone to tear into the engine and fix that knocking noise and put it back in the car, see if my problems go away? or just keep trying to correct it with this block?

 

Problem "fixed". The TPS evidentally wasnt set right even though the other dealership said they adjusted it right. So its now set at 5.0 volts, and fixed a couple vacuum hoses, main one was the PCV valve hose. The car is running great, a little high idle, about 900 in park, 700 in gear.. no check engine light and responds pretty well.