manzanman

I have an 80 California model with a 350 instead of the 305 which was the original engine. When the engine is cold it idles very nice but then when the choke and fast idle is off it will run rough. I have used some spray cleaner in the carb jets which sometimes helps with the hesitation on acceleration which is also a problem. I have also added a can of fuel cleaner to the tank which also helps with the hesitation issue but not the rough idle. It has had a recent tune-up with new wires, plugs, cap, etc. Anybody have any ideas? Thanks, Jay

a1sensei

Does it have the original E4ME computer controlled carb?
What is the idle speed when it is running rough?
Was it doing all of this before the tune up, or did it start then?

God bless, Sensei

manzanman

Yes Sensei, it is the original E4ME computer controlled carb that was rebuilt 2 years ago. I believe the idle speed was 1000. It was idling rough before the tune-up. The motor has about 7000 miles on it now.

RIJVETTES

The 1980 Q Jet carb had no computer control. That arrived in 1981. Your idle rpm is also very high- it should be closer to 600-650. Your carb may need some work.

a1sensei

1980 California cars had the computer Quadrajet.

It is possible the 350 needs a bit more fuel at idle than the original 305. Try turning out the idle mixture screws (if they are accessible). If it starts to smooth out, good.

Be warned though, the idle ports on these carbs are very restrictive stock, and sometimes you cannot get full rich idle control. If you cannot get it right, you may need to remove the throttle plate and drill the idle ports out with a 3/32" bit.

Ultimately, you want to find the point at which you have the highest manifold vacuum at your set idle rpms (which should probably be around 750 in neutral, not 1000).

God bless, Sensei

manzanman

Thanks Sensei, I don't think the mixture screws are very accessable but I will give that a try first. I really appreciate your help, Jay

J. Scott

I would think that a vacuum leak would show up when the engine is cold as well but have you checked that angle?

manzanman

Here's what happened. Engine has slight hesitation sometimes. It used to idle a little rough. I recently installed a new gas filter, tightened carb mounting bolts and air horn screws. Then I forgot to plug in the mixture control solenoid as a check engine light came on when I started it up. Plugged it in, started it up and it runs like crap. I have checked all my vacume hoses and other connections. Any ideas?

a1sensei

First, I always recommend putting Caig Deoxit contact cleaner on all the electrical connections on these old cars. You can buy it on Ebay. Just put a tad on each connector in the system (MC, TPS, Distributor connectors, Sensors, at the computer itself).

Then disconnect the battery for 30 seconds to re-set the computer.

If the problem started when you forgot to plug in the MC solenoid, re-setting the computer may fix it, but I'd still clean the contacts. It is time well spent to avoid frustration with these 28+ year old computer systems that are kept outdoors.

God bless, Sensei