Mixture control solenoid? 86 Cierra 2.8L

[jholub]

I've got a 86 Old Cutlass Cierra 2.8L with a carb on it.

When cold, it struggles to start. You can get it started, sometimes you might need to hold the gas to the floor (without any pumps). Once it is running, it runs poor: too low idle speed, some shaking, thick dark smoke, threatens to die. Once it's warm it runs ok...

It really starts and behaves (until you get it warm) like a car that is flooded. But it's not. At least not from pumping on the gas.

The problem started when my girlfriend was warming it up on a cold morning. She went inside after starting, came back out it was dead and wouldn't start. I found and fixed a small vacuum/fuel leak, that I thought might be causing the problem... but it might have been unrelated.

So maybe it was a sudden part failure. What part i dunno.

Background info:

• irregular idle speed: idle speeds up, then slows down, then speeds up...
• checked top dead center and found timing to be off by about half a cylinder (hope that makes sense)
• it would hesitate and about 30 mph shop replaced some kind of solenoid on carb which fixed the hesitation (MC solenoid?)
• new plugs, new wires, new coil, new fuel filter, new dist. cap/rotor... all seem to be ok
• damnit!

I'm starting to think that the mixture control solenoid is to blame. Anyone have any experience with this? The Chilton gives the procedure to check the MC solenoid. Too bad I have a Heynes. Anyone got any clues?

Thanks in advance!
John