I have developed a misfire at idle on one cylinder and it has me stumped. I changed the plugs, wires, cap and rotor and it's still doing it. It seems ok at high rev but at idle, it sounds like I have a dead cylinder.
Any ideas would be appreciated before I take it to a shop
Mark
Mark compression check next. Fred :)
Possable vacum leak at that cyl or burned ex valve.
Quote from: earthquake on April 17, 2009, 08:37:19 PM
Possable vacum leak at that cyl or burned ex valve.
Wouldnt a burnt valve cause it to smoke a little bit because there is no smoke. I did notice the number 2 plug having a different color than the other three. I am hoping that it's something simple but I will try and get it in to a shop next week. It's in the red wagon and I tend to baby it more than the rest.
Also, is it save to drive it a couple of miles round trip with it doing that?
THANKS FOR YOUR HELP?
I take it's a 78! (3?)
The electronic ignition on the late 70's Pintos are really dependable and put out a strong spark.
However, any marginal ignition parts will not be up to the task.
So if your cap, rotor, and wires have more than 25,000 miles or two years old, I would just change them for maintenance and see what happens. Motorcraft costs more, but worth it. The money is not wasted because you would have needed them soon anyway.
The cap, rotor, plugs and plug wires have less than 2000 miles (if that) on them. And yes, it's a 78 ;D
A burned valve will not cause it to smoke.A compression test will find this.As for the possable vacum leak take a spray bottle of water and spray along where the intake meets the head and listen for a change in idle.If the idle drops you got a leak.A vacum gauge can tell you all this also.
Recheck your firing order of your plug wires.
Buy a compression gauge. Check you compression. Check with the engine warm.
Change your PCV valve.
Check all the vacuum lines.
Tap on the EGR valve first . You may want to remove it and block it off with a plate for a test.
If the EGR has carbon and is stuck slightly open the car will act like that.
I really think this is the problem.
For your carb... With the air cleaner off and the engine running, rev the engine and then close the choke for a second. Sometimes this can un plug a jet. Now re-adjust the idle mixture screw.
Report back!
Thanks guys, I will try all of this stuff. I dont think the EGR vavle is there anymore because I know the air pump has been removed. But I will go over everything and see what happens. All I have to do is look at the engine in my coupe and compair :D
It must have been another bad wire or vacume leak because now she is purring like a kitten. It could be that she was just flat out jelous from all of the attention I have been showing the other two cars ;D
Thanks for your help
M
Mark, I am glad to have run across your post because my 77 is doing the exact same thing! Dropped in a distributor & got her running but now she has a missfire at idle. Going to buy some replacement plug wires & just leave them a bit long, even though I desperately hate that.