(Edit: I'm referring to my 84, which is running the factory computer controlled carb and emissions systems. I have the ZZ4 kit, which eliminates the EGR and EFE--other emissions systems are in place)

Originally my car idled like crap. I fixed that about two weeks ago by doing some carburetor work and making an interesting discovery. By the way, in case you're curious, if you have a second vacuum pull off, don't tap the line for the VAC/MAP sensor from the same line. Those pull-offs are of the "controlled vacuum leak" type, and that doesn't play nice with the sensor.

Anyhow, I got it idling nice and smooth, then the car tossed the alternator belt three times in three days. After the first toss it squealed like a pig too. I finally was sufficiently fed up with v-belts to swap to serpentine. I got everything back together on Monday.

However, the car has now decided it wants to have a cyclical, unstable idle. It'll sit at 900 (which was about where it was idling before), then slowly drop down until it almost stalls, then jump back up, rinse and repeat. If I crack the throttle manually to 1100 or so the motor is smooth as can be.

Here's what I changed in the process of swapping over to serpentine, aside from the serpentine brackets and accessories:

* Cut down my hard fuel line leading from the carb to three port regulator, used a longer piece of rubber hose to compensate.

* Swapped over to the newer AIR Divert valve which is required due to the serpentine configuration. Removed the vacuum lines that operated the old valve. Removed the vacuum "T" at the base of the carb that those lines ran too and instead ran the one line directly to the base. The old line had a hose clamp where it attached to the carb. The new one makes a sharp turn and has no clamp. (If I have a vacuum leak, it's probably here)

* Rewired the alternator wiring.

* Rerouted the engine ground. It used to ground on the v-belt alternator bracket. Now it grounds on the intake at the same location one of the two AC compressor braces bolts to.

* The four port purge valve for the EVAP system is sitting directly behind the tensioner. A few lines were rerouted to hold the valve in place, but no hoses were actually altered.

* The wiring for the AC is currently not hooked up.

* The AIR divert valve is not in the car because I'm looking for connectors (GM changed the plug style between the old and the new valve). The metal pipe is on the air pump and it is pumping air directly to the atmosphere

* None of the accessories seem to be making any unusual noises. All of the pulleys seem straight and have no wobble, even at 3000 rpm.

* The water pump and alternator are new. The PS pump is rebuilt, and the AIR pump and AC compressor are used.

* Both secondary braces are installed on the AC comp, but the one for the alternator was missing (looking for one this weekend).

The ONLY thing I can think of is a vacuum leak at this point. If anyone sees anything that points to something alse to look at, please let me know. I posted EVERYTHING I can think of that changed just in case there's something I missed.

 

I can't hear anything, actually...

Seriously, I'd check that charcoal canister tubing for a routing error. Otherwise, have you checked the IAB dwell? Is it wondering around while this is happening?

This is the full HO 350 conversion kit? I didn't realize it eliminated the EGR and EFE. I thought it used an external tube to bring exhaust gases up to the intake manifold via the old hot air choke boss.