skipping

[donm]

My car runs geat under power but when it's not under load, ie, at idle or if I hold the linkage open at a steady 2k rpm, the engine has a slight skip or miss to it. I had always thought this would indicate an electral issue but I replaced the plug wires, plugs, magnetic pick up, cap and rotor and it's still there. The pick up is gapped at .3-.4 mm, per spec. The plugs are gapped to spec, too. So, what else might cause this problem? Or is this just the way it is?

Could it be a fuel system issue after all? As I said, I can floor it and the car pulls nicely through the gears with lots of power and no skippping so wouldn't that rule out a fuel issue?

Any thoughts would be appreciated.

[124ADDHE]

Pls desribe your motor..carbs, ignition type, compression, everything you can.

I would lean towards a idle circuit issue/maybe a coil prob.

[donm]

Right, I forgot to mention it's the original 2000cc with stock carb and stock ignition set-up. The car runs so good I wouldn't expect there would be a compression problem. And I thought the idle circuit only came into play at idle, no? I also replaced the ignition control module to no effect. The only thing I didn't change is the coil. Do you think that might be the problem?

[majicwrench]

Don't change the coil, you have changed enough parts! If engine runs good under power ignition system probably fine.
The Idle circuit on these carb has a huge effect on the way they run cruising, a well as idle.
Does this happen on the road, or just when "I hold the linkage open at a steady 2k.."
You say the car "runs so good?? Describe a slight skip?

[donm]

Glad to hear you say that; I'm running out of cash. When I'm cruising as a steady speed, say 30-40mph, I can feel a slight hesitation every 2-3 seconds. It's very slight but it's there. When I step on the gas it accelerates fine with no hesitation whatsoever, all the way up to red line.

[majicwrench]

How does it idle??

[donm]

Their's an occasional hiccup or skip every few seconds. Maybe this is normal? The nature of the beast? I have no basis for comparison.

[azruss]

anytime i've had issues like that it is due to a small air leak on the intake side. If you are burning a lot of oil, you could be getting a temporary plug foul from leaks thru the valve guides. My vote is on a small air leak.

[SouthSwedeSpider]

I have exactly the same symptoms as you have, although I have a FI car. Haven't been able to find the problem, but I have also to 99 % ruled out ignition problems. Still no clues. The odd thing is that when I pulled the ignition leads to the plugs, one by one to see if I could identify a particular cylinder causing the problem, the spark to cyl # 1 was so strong I could not hold on to the lead even if I used gloves. Spark to cyl # 2-4 was much weaker, no problem to hold on to the leads. There was however no obvoius difference in idling regardless of which plug was pulled. Electrical hickup after all ??

[majicwrench]

South Swede,
' Pulling wires like that is not a great idea. That 30k volts has got to go somewhere. If it's not jumping the plug gap, it's climbing up your arm OR shorting to something else in the ignition system, like back thru the wiring to the ECM, or to some other plug wire terminal in the cap.
Easy way to do it, take 4 short hunks of fine wire, and either work one end tween the plug wire itself and the plug boot, or stick it up along side the plug tween the porcelin and the boot, and bend it in a "U" so it ends up sticking up. Obviously do this engine off! Now you have four wires sticking up from your four plugs. Take a test light, ground the glound clip, now with engine running touch probe to bare wires sticking up one at a time, and you will short that cylinder without shooting sparks thoughout the system.

[donm]

Thanks for the advice,all. I guess check for an airleak somewhere (spray carb cleaner around the carb, right?) and then maybe try to clean the jets. I can take the top of the carb off without removing it from the car, right? And then I should see the float and clean out that area along with the jets?

[majicwrench]

Spraying carb cleaner around is a good way to start fire. And the fumes will end up being sucked into carb, raising idle and making you think you have a leak.
Have you set the idle mixture?? And the only jet that really matters at idle/part throttle is the idle/low speed jet, no need to take the whole carb apart.
Keith

[donm]

I took out the idle stop thing and I couldn't get it apart but I cleaned the tiny orifices with carb cleaner and a strand of thin copper wire, and then I removed the mixture screw and sprayed carb cleaner and then compressed air through that circuit. But where is the "idle/low speed jet" that I should clean?

[donm]

I forgot to mention it's the original carb, a 28/32 ADHA, I think.

[dmwhiteoak]

I am having the same problem with mine. It a 32 adfa. I am in the process of rebuilding the carb now . Waiting on my rebuild kit that did not show today. I have also looked for vacuum leaks and found none that mattered. maybe together we can figure this out. when I tore down the carb everyting looked good and clean. Im about to pull what little hair I have left OUT! Keep me posted and I will do the same. Dennis