Or, one that displays many symptoms.

Here are the things I noticed about my car:
1.)Sometimes "diesels" after I try to shut it off (worse when hotter, but it's not overheating)

2.)Idle (in drive) "seeks" about 1-200rpm when fully warmed

3.)Manifold vacuum also "seeks" about 2-3 in Hg when warm at idle (between 16 and 19 in Hg)

4.)If I nail it under load @ low rpms it usually backfires through the carb, and doesn't seem to be downshifting right. If I bring up the rpms semi-gradually its OK.

5.)Overall the car feels a bit sluggish.

6.)May have a low rpm miss.

7.)Car is a bit hard to start when cold.

Plugs & wires are new, cap & rotor are fine. Carb is a remanufactured one from national auto (which seemed to be very clean and high quality BTW, the guy said they just switched their supplier)

Now some of you may have read my posts about my rockers coming loose, well I got them to stay finally (I think - still have to check the passenger side valve cover. Drivers side rockers stayed tight)

Could all these problems be caused by the mixture? Would it be rich or lean? Since it feels like a miss but the ignition is fine, does that mean rockers again?

P.S. Initial Timing is set @12*, DR secondary rods, K hanger, loose secondary spring tension. (reposting this cause it got buried on the tech/general engine board, and I think i)t may be carb related.

 

I'm guessing that the dieseling problem could be due to excess carbon coating the combustion chamber. The carbon could be from a rich fuel mixture? Anyone else have some ideas?

 

The problems all sound consistent with a vacuum leak and lean condition to me. Dieseling and idle seeking are two very common symptoms of a vacuum leak.

 

I'd say that with the vacuum dancing you may have a rocker too tight, you also might want to check on that timing, I think 12* is a bit excessive(you may want to try 6*)

 

Your timing is too advanced and your carb mixture is not adjusted properly. Get these issues fixed and it will go away.

Timing advanced too far = backfire & sometimes run-on

Vacuum seeking a few inches = mixture not balanced between both banks

high idle can also make your car run-on as well.

If the car starts ok(not sluggish) when it's warm your initial timing is ok where it is. Check your total timing and the shape/type of advance springs in that distributor.

BTW a tight rocker usually causes a rapidly pulsating vacuum reading.

 

thanks guys,
All these problems happened when the initial timing was set at 6* also. I just recently set it at 12* adv. and it seemed to run better so I kept it there. still occasionally backfires. The vacuum isn't pulsating rapidly. As far as hard cold starting and run-on, I think I saw someone else say that this could be caused by something on the bottom of the carb leaking, therefore supplying fuel after the car is shut off and draining the fuel bowl so it has to refill before it starts. does this sound right? How Do I fix it?
Maybe I have this problem on my remanufactured carb, plus a vacuum leak somewhere?
I don't think the timing is too far advanced, cause it starts up fine once warm and I don't get any knocks with 89 octane. also the choke plate snaps shut fine when its supposed to.

 

Well guys, I took off the carb a couple minutes after I warmed it up, and there was still gas mist in the intake manifold (or gasoline liquid dripping onto the hot manifold vaporizing it) Either way I don't think this is normal is it? I looked at the bottom of the carb (still fuel in the bowl) and it was leaking from somewhere. When I tilted the carb more than say, 15* or some tiny amount, fuel poured out of what looked like the primaries. Does this mean the float is too high? Primaries leaking? what?

Also, I took o2 readings while it was warming and when it was warm and it seemed right in the middle while warming up and once warm, at idle it was in the .050V range.

the things I think that I was referring to in the last post (the cylinder-looking things on the bottom of the carb right in the center of all four barrels) were already epoxied over by the remanufacturer, so thats not the problem. The fuel is definitely coming from the primary area.

Thanks!
John

 

The place that Q-jets commonly leak fuel is the plugs at the bottom of the fuel bowl. Been a while since i looked at the baseplate of one, but IIRC you can see e'm sticking down from the carbn manin body in the center in front of the primariues. There will be little protrusions w/ lead covering them (again, IIRC) If you want to check these while the carb is off, wait till it's dry. Then fill it up w/ fuel (carefullly pour fuel intop the slot between the primaries and secondaries. And see if those plugs get wet. If so you'll need to plug it up w/ some epoxy or something similar.

I doubt thats your problem though. The surging and diesling are probably both caused by a serious vacuum leak. Normally you'd check the carb bolts to make sure they were tight first (btw, don't forget a new, proper gasket when you go back in, your car should use the spacer style. After that, while it's running spray some carb cleaner around the intake to head mating surface, around / on all the vacuum hoses, etc. If the idle speed surges up noticeably, it's leaking there.
Once you're sure you've gotten rid of all the vac leaks, make sur ethe TPS is set right and good. If your O2 sensor is good as well, at this point you should be in good shape.
I mention the TPS cuz ithey always fail on CCCS cars. That combined w/ a nasty vacuum leak would really contrribute to your dieseling problem. Once the TPS fails, it basically runs too rich all the time, which will seriously carbon up the chambers, which lends the 'spark' for dieseling.