Replaced plugs and wires, but still has a skip.

Hi All.

I have been working on my dad's 1986 Buick Electra wagon with the 307 engine and when I bought the car and drove it to him, it did not skip or miss at all. Now, when it is started up there is a noticeable skip from cold idle into idling warmed up.

I decided to do a quick tune up on the car and replace the usual suspects: plugs, wires, cap and rotor. I forgot the coil is on top of the cap, so I don't know if my dad bought the coil as well. Yesterday even though it was 20 degrees in IL, I replaced the plugs and wires, but not the distributor cap and rotor. Started the car up and the skip is still there even though the car ran smoother. Assuming the obvious, can a worn cap and coil cause a skip/miss? I would think if the cap/rotor and/or coil were bad, it would run like crap on all 8 cylinders.

I would have replaced everything, but I ran out of time and steam. Going to have his mechanic diagnose the problem. I also thought it could be a stuck lifter or valve. Broken valve spring is not likely since there are no odd smells or smoke out the exhaust.

Any suggestions from members who are familiar with the infamous GM 307 would be great.

Thanks,

Ted

 

You said it skips from cold idle into idle warming up? Does that mean at some point it stops skipping? a bad cap and button could be your culprit and you outta be able to take that coil off the top of the rotor cap and put it on the new one. A bad coil is doubtful IMO. How’s power? You should be able to tell if that cap and button are the culprit just by looking under there. If anything looks even slightly corroded swap that joker out.

 

Hi Grizz:

I mean it starts with a skip and it doesn't go away. I know I should change the cap, coil and rotor before posting, but since it is only skipping/missing on one cylinder ( I assume) wouldn't that rule out those parts I didn't replace that would seem to cause those issues on each cylinder?

I should have just replaced everything and then continued my diagnosis. Has anyone heard of a valve sticking or hydraulic lifter collapsing on this engine? From my experience it is pretty bullet proof. I guess anything is possible after the car sat for several years in a garage undriven.

Ted

 

If it's sat several years don't rule out bad modern fuel. Could be crude in the carb, fuel filter, or pick up screen plugged in tank.
Even my lawn mower ran fine in Florida. Last winter in Illinois and the carb needed rebuilt.

 

Already drained the tank and replaced the fuel filter. If the car sputtered and didn't idle worth a darn I'd tend to agree. The skipping/missing issue is either electrical or could be a stuck valve or worse, broken valve spring. I hate throwing parts at a problem, but in this case they need to be replaced anyways. Will post when it gets fixed.

 

Do a compression test. Don't go throwing money into electrical/ignition components until you've determined the actual condition of the engine. All cylinders should be within 10% of one another.

Also, if modern motor oils or synthetics have been used instead of an oil with a zinc additive, you could have a worn cam lobe.

 

Don’t buy that coil! Not yet anyway. And besides you outta be able to ohm test it? I was gonna say fuel filter but that’s ruled out. You’d be surprised how the metal bits on those caps and buttons corrode, especially after sitting any where with a lot of moisture. Other things to check are the idle air control valve and p.c.v. valve. These are easy fixes and probably get both for around $20. A car like that, that’s been sitting a while I would sell a pcv valve (or throw it in for the price of the part at least) when doing a minor plug/wire tune up. Take pictures of that cap and button! Just for “s’s & g’s”

 

My dad's 83 Olds was doing the same thing. It was driving me bananas. I switched plugs, wires, cap, rotor, etc. Some of them a couple times. It eventually got worse. I went through the trouble of tearing down the top of the engine to try to find something wrong. In the end it was the mechanical advance sticking. I fixed it by installing a new distributor, because his was in bad shape.

 

If it was a valve, lifter or spring problem you would know it.

 

That would be constant, and noisy, except that a lifter that bleeds down then pumps up once hot could be a cause. Does the misfire sound like a mechanical 'tick?' And an '86 is the C3 setup, so there shouldn't be mechanical or vacuum advance, although I've seen a couple 307's with the electronics removed. I also think the coil is good enough, as it would cause a loss of power or shut the engine down if it had problems. So, a compression test is in order; the cap and rotor should only be replaced if they have 60K or visible damage on them.

 

A thought just occured to me: if the engine's 'misfire' is making noise, is it separate from the 'tictictictictic' of the mixture control solenoid? If the solenoid is cutting out once the engine's warm, it could be mistaken for a misfire when cold.

 

Make sure you put the plug wires back on correctly and separated them correctly , also proper installation of all the parts. I'd also try putting the old wires/plugs/parts back on one at a time and see if it stops in phases, new doesn't always mean good.
Check the engine ground/s as usual.

 

^^^indeed,before I start I always sketch a quick diagram of the cylinder #s and their corresponding place on the cap. If that makes sense?

 

Yes, you can do that, or mark each wire with the corresponding cylinder number, and keep each bank grouped together, as you remove the cap and wires, then use it to figure out which wire goes where.

 

Do the cap and rotor first. Those 307's have about 10,000 vacuum lines as well, and you might make a weekend project of replacing them all. Just get a roll of hose and replace one at a time, cutting to size. I've had four Olds 307's and know that process well...