86 caprice misfires

[ruberpoliceman]

It's a 1986 caprice sadan 4bbl. Runs fine when idling or reving in park or neutral but wants 2 misfire while driving, this usually doesnt happen until about 3rd gear or overdrive especialy at low rpms. I just put in Bosch double plat. plugs and the wires dont even have a year of wear on them as well as the fuel filter. I beleive it has something 2 do with the distributor guts. While its running you can hear a slight ticking coming from the distributor area like there is an arc, im not sure what this is because i havent taken the time 2 remove the dist. cap yet. Was wondering if any of you guys have had the same problem or know of what might b causing this, also i replaced the pickup coil and distributor cap as well as the rotor and neither have over a year on them. any help is appreciated. thanks.

[silicon212]

Originally Posted by ruberpoliceman

It's a 1986 caprice sadan 4bbl. Runs fine when idling or reving in park or neutral but wants 2 misfire while driving, this usually doesnt happen until about 3rd gear or overdrive especialy at low rpms. I just put in Bosch double plat. plugs and the wires dont even have a year of wear on them as well as the fuel filter. I beleive it has something 2 do with the distributor guts. While its running you can hear a slight ticking coming from the distributor area like there is an arc, im not sure what this is because i havent taken the time 2 remove the dist. cap yet. Was wondering if any of you guys have had the same problem or know of what might b causing this, also i replaced the pickup coil and distributor cap as well as the rotor and neither have over a year on them. any help is appreciated. thanks.

Check for vacuum leaks, also do a compression check. If it was ignition related, it wouldn't be happening at one point and at no other.

[capriceowns]

I had a similar problem on mine, were at idle it missed fire and sometimes felt like a cylinder was dead, same when in drive at a complete stop, but once you gave it gas it went away completely

I had a cracked Tee fitting off my carb.

Look on the front of your car (the side facing the grill) at the BASE of the carb should be a hose about 2 in going into a Vaccum tee, the larger hose goes to the right to the PCV valve, and the smaller hose goes from the tee left up to the bottom of the bell housing(were the air filter sits)

My tee got old and hard and cracked, then when I took it off it shattered.

I'd check yours out and see if its ok.

idk if its whats wrong with your engine, but in the future this may help

[ruberpoliceman]

T is good, All vaccum lines are either plugged or connected 2 the computer controlled shit, still thinkin its somethin in the dist. maybe i'll find the problem when i take the cap off. Also it does it on and off, like somtimes it will run fine, then for no apparent reason itll start jumping (misfiring) usually only while your driving. Sometimes if i drop it in nuetral and pump the gas itll clear it up. Keep the ideas coming though, any suggestions are appreciated. Thanks.

[ruberpoliceman]

Oh yea, as far as Vaccum goes, The fact that one of my carb bolts broke off in the intake could contribute to that being the problem, not realy sure if that would cause it though because the other three are in pretty tight but i dont know, I guess i'll put the extractor 2 it when i get some time and throw another bolt in. Oh yea also the compression is good on all cylinders.

[silicon212]

Carburetor. Mark my words.

Don't ask me how I personally know this.

[ruberpoliceman]

(im assuming your saying the missing bolt is the problem) Very plausible, i'll give it a go when i get tired of it missfiring and let you know how things go.

[silicon212]

Originally Posted by ruberpoliceman

(im assuming your saying the missing bolt is the problem) Very plausible, i'll give it a go when i get tired of it missfiring and let you know how things go.

The missing bolt is a big problem, but it took a bit to jog my memory on this issue - the idle air bleed circuit on my E4ME carb (yours will be the same model if it's not modified) caused endless grief with me until I diagnosed the problem. It was gunked up with carbon and causing problems not unlike you're reporting in this thread. A complete carburetor overhaul with a full cleaning solved my problem. This was a couple of years back.

[ruberpoliceman]

well i just rebuilt my carb not 2 long ago which i forgot 2 add. But im not 2 sure exactly where the "idle air bleed circuit" is located, Im pretty sure i cleaned the whole carb up pretty nicely though. But yea i'll fix the bolt and see how things work out.

[silicon212]

Originally Posted by ruberpoliceman

well i just rebuilt my carb not 2 long ago which i forgot 2 add. But im not 2 sure exactly where the "idle air bleed circuit" is located, Im pretty sure i cleaned the whole carb up pretty nicely though. But yea i'll fix the bolt and see how things work out.

The idle air bleed circuit adjustment is under a plate that's in the location where the bowl vent used to be.
Clean out all passages in this area.

[ruberpoliceman]

Alright, i dont think i did anything with those when i dissasembled it. How does that come apart? the tab thing just pops off or do you have 2 take the carb apart?

[silicon212]

Originally Posted by ruberpoliceman

Alright, i dont think i did anything with those when i dissasembled it. How does that come apart? the tab thing just pops off or do you have 2 take the carb apart?

There are rivets on either side of the tab that you will need to drill out. You can simply leave the tab off when you are done.

To properly clean the idle air bleed circuit, you will need to disassemble the carb.

[ruberpoliceman]

Thanks. I'll try that.

[ruberpoliceman]

Ok i did that and the valve itself had a little carbon buildup on it but nothing major. Whats the setting for it? i just stuck it back in there 2 about where it was. And it still misfires but that could be an endless operation as to find out whats causing it.

[400wagon]

Have you checked your plugs recently? I went through almost the exact same thing this past week.

A year ago I put brand new platinum plugs in my 85 wagon. About 2 weeks ago I started having a misfire. I replaced all the plug wires, which by the way, were less than a year old - a little better for a day or so.

Put a hotter coil in it - better for about 2 minutes of driving, then a dead cylinder.

Pulled the plugs - one was fouled and completely covered in carbon/sludge stuff. I know my car runs a little rich, but have never had this problem before.

I have also heard that our cars don't really like the platinum plugs for some reason, and the double tip or whatever plugs are just a gimmick - may actually be worse for the car - they cause hot spots and detonation. I switched from my platinum plugs back to the plain ac delco plugs.

Just something to check, may not be the problem on your car.