CNCREG

I have a 92 RS that when you first crank it runs up to like 1200-1400 rpm for about 30 seconds. Then after it warms up in Park it is around 750 rpms' the when you put it in gear it's at around 500 rpm's. When your sitting at a light it runs rough (like a miss or skipping) and when you give it gas it has a hestiation before it takes of. Once you get going it runs fine but as soon as you come to a stop it drops back down and does it again. Once it's warms it runs like that whether it's in park at 750 rpm or in gear at 500 rpm. It had a heating issue before but never ran hot (boiled the radiator) just hotter than I thought it should. Anyone had similar experience and knows what's up?

CNCREG

Power and gas mileage are fine. That's what's so whacky about the whole thing. Once you get rolling it runs like a top.

The check engine light has only come on like twice in the last months and only for a few minutes then back out.

One thing though IAC?? what is that?

Pro

Idle air control if I remember correctly.
Your TBI is similar to the one in my truck. I had the same issues and had to replace the EGR silenoid. That helped out so much.

But recently, the radiator fluid outlet on the back of my intake started to leak, and soaked the front part of the distrib cap and plug wires. So I am having similar issues. So you might just want to do a completely tuneup like I am going to have to do soon.

aklim

Find out what code it displays. Also un the engine at night and spray a fine water mist at the wires. If they light up at all, replace them. Make sure you have no vacuum leaks bu spraying brake cleaner at the hoses and joints. If RPM goes up, check that area for a leak. Make sure the brake booster hose and system is not leaking. You have rounded up the usual suspects? Plugs, cap & Rotor, air filter and fuel filter?

ULTM8Z

Oh man... did I ever fight a problem like that!!! For a year!!!!!!

What I found out was that my fuel tank vent lines must have been blocked and as a result my charcoal cannister was not doing its job. I took all of the vent lines off, sprayed carburetor cleaner through them and then blew them out with compressed air.

But before I found that out, I ran through the ignition, fuel system, heads, valvetrain, manifold gaskets, wiring harness, ECM, sensors... practically anything that was even remotely connected with the engine, but I could never get rid of the idle misfire. Just like yours, it would idle like garbage, but as soon as I got up and rolling, it was fine.

CNCREG

Thanks for all the input guys. GUESS WHATTTTT? It was a 1/4"ish vaccum line that runs from the egg shaped 'T' that comes from the brake booster behind the distributor and goes off to who knows where one way and to a manifold vaccum tube the other. Well the line was split on the bottom side. I had sprayed with it running adn no pick up of te idle but I was moving another line adn it lifted this one a little and i heard the tell tale hssssssss. lol Anyway fixed and running smooth again.

thanks, guys