I have a 1989 f150, 300 c.i., 4x2, 4 speed man. trans. w/ O.D. I have been having what seems like a slight irratic missfire, idle speed, and a slight rough idle problems. I have new plugs, wires, cap, rotor, air & fuel filter (changed withing the last 7k miles). I have cleaned the idle air control, throttle body, and egr valve. I have also run injector cleaner several times. I have had a few suggestions of what might be causing my problems but dont know which rout I should take. I have been told it could be the ignition coil, ignition module, or map sensor. The missfire at the moment is my main concern once that is fixed I will address the idle unless it fixes both problems with one solution. I also suspect it may be due to buying cheap tune up parts but dont believe that 100%. This problem has been ongoing for quite some time but now seems to be getting worse in the last couple of days, I would only notice these problems when the truck was parked but now seems to occasionally missfire while driving, before this occurred the truck seemed to drive just fine. I did have problems with the idle air control with the idle fluctuating quite a bit when truck was cold, but cleaned it, and now seems to work fine and the egr valve was causing my check engine light to come on which showed up as the only problem on the computer analysis but I cleaned that and tested it and seems to be fine also. I would greatly appreciate any input on this issue if I have left out any details that could help determine my problem please let me know.

 

When you put the new plug wires on, was the connection on the coil all chalky ? If so that's likely the culprit, Generally, every time I've gone that far in a tuneup I went ahead and replaced the coil since it's right there anyway just to be sure,, the control module could be the bugger too, but alot of times for me personally it caused startup issues more than an erratic misfire.

 

yes it was chalky but I went ahead and cleaned it the best I could dont know if that helps or not in this case, but at the moment I have been leaning more towards the problem is the coil myself, thank you very much for responding I feel it helps a lot to get others input on issues I dont have much experience with.

 

Anytime, glad I could be of help. I'd definitely replace the coil though, I'm going to bet that's the real issue you're having. All that buildup on the coil causes major restriction on the electrical flow which in turn means more heat buildup inside the coil itself causing breakdown. Electrical parts really don't like massive heat over long periods of time,, and always remember..

Everything electrical is made of smoke,,, when you let the smoke out,, it's toast. lol

 

Just wanted to let you know that made a huge difference truck is running good now seems to have a lot more pep than its ever had. Thank you again for your help.