Hi all, I have 1986 5.0L 305 TPI engine in my Camaro (the engine is an LB9, 700 R4 auto) and I'm having a LOT of trouble with the idle. When got the car, it idled at around 1500 RPMs in PARK, so my father lowered the idle speed to around 1000 or so RPMs. Well, because of that, the car runs like sh*t now. I don't understand what is up. In DRIVE, the things is almost ready to die on me! Now, my father is a mechanic, and based on his 30-plus years of experience, he said 1500 RPMs in PARK is way too high. Yet my friend had a 1989 RS with a 5.0 TBI and his idled at 1500 RPMs, with an automatic transmission. My other friend has a 1987 IROC with a 5.0 TPI engine, and his idles at 1500 RPMs, but since he has a standard tranny, I dunno what position it would idle at for 1500 RPMs. The RPMs drop to just uner 1000 when I put my car in DRIVE or REVERSE before my dad screwed around with the idle.

Now, my question is, what is the correct idle of my car, according to General Motors? Any site I can go to where I can get this data so I can show it to my dad and prove to him that fixing my idle was wrong? I mean, he has NEVER had to work on a fuel-injected car before; it's all carburetors and stuff for him.

Is my father right; should the car idle at like 1000 RPMs in PARK? Or should it be the 1500 RPMs I think it should be?

Also, one other thing; when I put my car in DRIVE or REVERSE, the whole car like bucks forward violently. It only did this with the RPMs at 1500. Is that bucking because the RPMs are too high, or is it something else? Is it normal?

Thanks all

Kev

 

1,500 is to high

If i remember right the ECM set "target idle" is about 800rpms warm.

Your car will race when you start it but the idle should come down and settle somewhere around there, and in drive should be 600rpms. You'r dad is "righter" but i question how he "set your idle' I'd check for vacuum leaks, I'd check also to see if the IAC is sticking, and if the throttle blades are sticking as well. The car should be much lower, but ways of fixing it aren't usually by "mechanical" adjustment, there's very little you can do with the iac screw, if you want to jump your idle up or down the CORRECT way is by prom tuning.

Try to find the PROBLEM to be fixed, look for vac leaks/sticky valves/sensors

good luck

 

To be technical: the only way to "set your idle" is with a PROM change. The screw on the throttle body actually sets "minumum air" which is like it sounds: it sets the blades to limit the lowest (minumum) amount of air into the engine, which at that point, the IAC motor controls the amount if air coming into the engine during idle (hence "Idle Air Control motor").

The car is going to idle like crap whenever you move that screw because the IAC motor is trying to compensate past it's limit. Also, it sounds like your dad didn't adjust the TPS voltage afterwards, which is effected whenever you adjust the minumum air screw.

Go through the procedure of setting the minumum air, then TPS voltage, and see if that fixes it. If not, try setting your timing first, then the rest of it, in addition to cleaning out the IAC passages. This is all assuming the rest of the motor is in top working condition and nothing is wrong with a part somewhere in the scheme of things.