Bad spark plug?
Misfire Problem
OK,
So,
After all my efforts/problems (changing engines, oil pump valve falling out=no oil pressure, etc etc etc) I've still got a miss.
I put my stethoscope on all four injectors and they were making a nice clicking noise like they should.
My distributor cap and rotor were looking pretty crummy and old so I replaced those today and it still missed.
I measured the resistance of all four spark plug wires and those were good too.
I hooked up the timing light to all four spark plug wires and all 4 showed spark.
So I pulled the plugs.... Number three looks BRAND NEW. Like it has never fired on that cylinder.
Tomorrow I'm gonna hook up a test lamp to the injector plug to see that it's getting a signal and measure the resistance of the injector itself.
Anybody got any more Ideas?
-Eric
So,
After all my efforts/problems (changing engines, oil pump valve falling out=no oil pressure, etc etc etc) I've still got a miss.
I put my stethoscope on all four injectors and they were making a nice clicking noise like they should.
My distributor cap and rotor were looking pretty crummy and old so I replaced those today and it still missed.
I measured the resistance of all four spark plug wires and those were good too.
I hooked up the timing light to all four spark plug wires and all 4 showed spark.
So I pulled the plugs.... Number three looks BRAND NEW. Like it has never fired on that cylinder.
Tomorrow I'm gonna hook up a test lamp to the injector plug to see that it's getting a signal and measure the resistance of the injector itself.
Anybody got any more Ideas?
-Eric
1 - 7 of 7 Posts
The resistance came out ok, and when I hooked up a timing light it flashed. And timing lights fire by current, and in order for there to be current it has to spark.86AW11 said:Bad spark plug?
So I really don't think the spark plug is bad. I am planning on pulling it and letting it spark externally tonight so I can see the spark.
Anybody ever heard of a plugged injector?
Yes.ewaustin said:Anybody ever heard of a plugged injector?
Witchhunter performance (a board sponsor) does a fantastic job of testing/cleaning fuel injectors.
Did you find soluton? I have a pretty bad misfire at cold / warmup, gets a little better when warm when RPMs go above 3000 but car lurches off a dead stop due to the missed pulses. Runs fine at high RPM / WOT so I don't suspect injectors but I might be wrong
The spark is not necessarily at the points of the plug, however. A defective insulator can flash over. That is a common ignition failure.The resistance came out ok, and when I hooked up a timing light it flashed. And timing lights fire by current, and in order for there to be current it has to spark...
You didn't say which car you had. If it is a '85-'86, then the fuel injector connectors have latches that are extremely fragile, and most likely they are broken. This means that the connectors can back off the injectors, and that is a common cause of intermittent misfiring.
Check compression of all cylinders. Replace all of the high voltage ignition components: Cap, rotor, wires, and plugs. There is no practical way to evaluate these components except for replacement with new. Also, see above.... I have a pretty bad misfire at cold / warmup...
1 - 7 of 7 Posts
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