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OK , my car missed a couple times two weeks ago and slowly started getting worse and occuring moew often. My vavles are fine , lifters are fine. we changed spark plugs and wires because wires were old and the 3 month old spark plugs were shot because a lil too much gas, but the car ran fine before. this past winter i put a new cap and rotor on my motor so what the heck is wrong? the timing is fine. the motor is missing and backfiring at random. PLease help
Did you verify that the cap is clean, dry, and has no cracks on the inside when you installed it? Any moisture in the cap can cause a misfire.
Did you use the dielectric grease on the boots at both ends?
Have you had the car running at night with the lights off and the hood up so you can see if there is any kind of random spark coming off the plug wires by the exhaust manifolds or plug wire looms on the valve covers? Have a buddy tap the throttle occasionally while you are doing this.
*This is very important. Make sure you are no where near any moving part when you do this (like the pulleys and belts)*
Just because the plug wires are new doesn't mean one didn't get nicked or cut... or was bad right out of the box.
Does the mis change as the car heats up? as in gets worse?
Ignition modules and coils as they age and start to go bad first show their problems as the engine (and the part that is bad) gets warmer.
Did the miss start after you changed the plugs? It could be that you have a cracked insulator on one of the plugs.
The car misses when it first starts up then again when it gets warm. The car has been missing before and after we changed the plugs. When the car very first started missing it was when it was warmed up.
The cap is fine no cracks or moisture, no build up on the rotor button nothing , and i have had the car running at night with the lights off and there were no sparks or arcing. I thank you all very much for your time
Well, we are here then...
COuld still be electrical in nature. When it is missing, you can remove one plug wire at a time - if you remove a wire from a running cylinder, teh engine will miss worse. if you remove a wire from a non-running cylinder, nothing will change. NOW you have isolated teh problem cylinder (be it mechanical or electrcial, you've found the bad one).
check that plug. replace that plug. same with wire. (IF you swap them to another cylinder, do ONE AT A TIEM (plug only, if problem moves it is the plug. not move, then try teh wire, etc).
If by chance you seem to be going in circles, it may be the coil (that is my guess at this at this time). If the problem seems to move from cylinder to cylinder (you cannot pinpoint 1 or 2 bad cylinders) then chage the coil.
You changed the plugs you said...fouled by too much gas or too little spark? Did the all look about teh same? How did they look?
You have checked all the vac lines - no leaks, cracks, splits, hooked up to the proper places, etc? Double check!
More questions if this don't fix it....let us know
Well everyone i fixed my problem. a coil in working order should have 500 - 1500 ohms, well i tested my old one it was putting out .8 ohms so there was an issue. also my carburator is running rich after down jetting it so if anyone needs a edelbrock proformer 650 cfm 4 barrel with elc choke ill sell it for 225.00