Probably buying an 87 Caprice, Centerbolt LG4.
Anyway, It's got a CCQ-Jet, and it diesels, bad.

The trusty haynes manual says dieseling is one of 5 things.

1 High idle speed
2 Electronic solenoid at side of carb not functioning properly.
3 Bad timing
4 Bad THERMAC (WTF, Like that would reall make a difference..)
5 Engine too hot.

I'm gonna rule out the THERMAC, timing and operating temp for the purposes of this post.

Since I'm too lazy to research this one, kinda busy lately, I need some info.

The mixture control solenoid is goverend by the ECM via O2 sensor, I'll assume Coolant temp sensor, and what else?

The "Electronic Solenoid" at the side of the carb, what is that?

Next topic, The idle is REAL rough, we're talking 72 F100 with bad shocks on a field full of ground hog holes rough.

Third topic, the AIR line running to the cat, has blown out, it looks like someone taped a firecracker to it and burst a hole in the stainless line.

I'm trying to find the correlation, but I'm not seeing it. I'm pretty much sure the O2 has never been changed after 130K miles. But how detrimental to the CCQ-Jet system is the O2?

 

AS far as the diseling goes "BAD GAS" would be my first guess. "Low octane or water"
Second would be the timing is off. With the 4 wire harness on the distributer disconected it should be at 6.
I would get the 02 sensor replaced. The steel line that is broken can be repared with a rubber hose and a couple of clamps.

 

I could care less about the AIR line to the cat, that's all getting gutted ASAP.

I'm more concerned as to the correlation, maybe a plugged cat?

 

The electronic solenoid at the side of the carb in some applications is an idle speed solenoid.

This can be of 3 varieties:

1. (Most common) An A/C idle speed compensator solenoid. When you flip on the A/C the solenoid is energized, the plunger pushes out, and idle speed is brought up a few hundred RPMs to compensate for the extra load of the A/C compressor. it does so by pushing the throttle arm a fraction of an inch open from normal curb idle speed.

2. An anti-dieceling solenoid. When the engine is RUNNING (any conditions) the somenoid is energized and advances the idle to a normal idle speed. When the engine is turned OFF, it retracts, shutting the throttle completely and eliminating any chance of the engine dieseling.

3. A true idle pseed solenoid. It's not just an on-off solenoid- it's actually a stepper-motor will a wide range of movement. It takes it's cues from the ECM to set idle speed where the ECM wants it. Very rare applications. i don't think the Caprice ever used a setup like this.

If what you just posted (the list) is stright from the service manual for your particular car then you probably have solenoid type #2. However, it's easy to determine for yourself. Just check to see when and under what conditions power is sent to the solenoid with a voltmeter.