Tech help: High speed miss that turned into a no start.
#1
03-05-2013, 06:12 PM
Tech help: High speed miss that turned into a no start.
97 Blazer 4 door 4X4......
Over the last couple years have been fighting a high speed (55 mph +) miss that started out as a surge at 60+ mph. It progressed and got to where it wouldn't go over 55 without bucking and jerking.
Fuel pressure was fine and a tune up resulted in no improvement. Fuel filter, plugs, wires, cap, rotor etc. The transmission failed and was rebuilt with no change in the high speed miss.
Last week my daughter was driving it and it quit running and wouldn't start. It was towed back to me and I found that the coil had failed after doing power, resistance and signal tests. Absolutely no spark at the coil.
After changing the coil I was convinced the problem solved, and although it wanted to start it still wouldn't. Fuel pressure was at 61 psi and new plugs installed, still didn't resolve the no start. I used a induction pick up to detect a signal at the coil wire to verify that the new coil was in fact working.
After checking for a hot spark, which I did have at the coil, I found a weak spark at the spark plugs. So the distributor was suspect now. After taking the cap off I saw a dusty coating on the rotor at the center. I removed the rotor and found signs of arcing under the rotor so I changed the cap and rotor and soon the engine was running with no high speed miss anymore.......
I have come to the conclusion that the coil was causing the high speed miss but then the low quality cap and rotor, that I had installed, was a compounding problem that created the no start after the coil failed.
Over the last couple years have been fighting a high speed (55 mph +) miss that started out as a surge at 60+ mph. It progressed and got to where it wouldn't go over 55 without bucking and jerking.
Fuel pressure was fine and a tune up resulted in no improvement. Fuel filter, plugs, wires, cap, rotor etc. The transmission failed and was rebuilt with no change in the high speed miss.
Last week my daughter was driving it and it quit running and wouldn't start. It was towed back to me and I found that the coil had failed after doing power, resistance and signal tests. Absolutely no spark at the coil.
After changing the coil I was convinced the problem solved, and although it wanted to start it still wouldn't. Fuel pressure was at 61 psi and new plugs installed, still didn't resolve the no start. I used a induction pick up to detect a signal at the coil wire to verify that the new coil was in fact working.
After checking for a hot spark, which I did have at the coil, I found a weak spark at the spark plugs. So the distributor was suspect now. After taking the cap off I saw a dusty coating on the rotor at the center. I removed the rotor and found signs of arcing under the rotor so I changed the cap and rotor and soon the engine was running with no high speed miss anymore.......
I have come to the conclusion that the coil was causing the high speed miss but then the low quality cap and rotor, that I had installed, was a compounding problem that created the no start after the coil failed.
#2
03-05-2013, 08:29 PM
Likely it was the other way around: the cap was causing the miss which caused the coil to go. These things are real fussy when it comes to cap & rotor. Aftermarket stuff doesn't last, stick with AC Delco tune up parts. Make sure you put a dab of silicone delectric grease on the terminals of the cap, both inside and out. Most of the time when a cap fails, it's due to camshaft retard not being within specs. The farther off it is, the larger the gap between the rotor segment and the cap terminal when the coil fires, which puts a greater load on the coil causing it to fail prematurely.
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