Pronto
Believe nothing you hear and half of what you see.
- Joined
- Dec 9, 2002
Do you have a spare coilpack? This is from Vortex Buicks:
Misses, or Backfires under Boost
If the car runs okay in light throttle conditions but starts to miss when the boost comes on, this is often a bad coil pack, and, sometimes, a bad module. The best way to test the coil and module is by using a Caspers coil and module tester as this stresses both and the spark will break down as the rpm on the tester is increased. The Casper's tester does not work on aftermarket modules, however. The car will run when started, but, if the tester is used, there will be no spark at all...then you know you have an aftermarket module. If you don't have the tester, then you can use a meter and check the resistance across each coil pack (between the two plug wire terminals on a given coil pack) when it is hot from running. The resistance should fall between 11-13,000 ohms on a good Type I coil pack. Type I is the original coil used on our cars...one piece unit with three individual coils molded into it. This is only a test of the coil packs and not the module and is probably about 85% reliable. Sometimes a coil will pass this resistance test but still fail under boost. The best test outside the Casper's tester is to swap a known good coil and module onto the car. I have never seen one that failed the resistance test to be anything but bad.
If the scan tool is reporting timing retard, detonation may be causing the problem, but, typically, this will not be as severe as a bad coil or module and the symptoms will not be as obvious.
At times, a loose balancer, or misadjusted crank sensor can cause an obvious miss at higher rpm. It is always a good idea to check the crank sensor for proper clearance on all three blades of the damper and to check the damper for wobble or movement when the engine is revved up.
A bad cam sensor can also cause a problem. Sometimes this becomes obvious after the car has been driven awhile. If the cam sensor has been out of the car and reinstalled, be sure it was properly installed and not on the edge of the window, or 180 degrees out. Sometimes, unplugging the cam sensor after the car is running will cause the car to run better. This is normally a sign of some problem with the sensor.
See the note in the next section about the cam sensor-
Misses, or Backfires under Boost
If the car runs okay in light throttle conditions but starts to miss when the boost comes on, this is often a bad coil pack, and, sometimes, a bad module. The best way to test the coil and module is by using a Caspers coil and module tester as this stresses both and the spark will break down as the rpm on the tester is increased. The Casper's tester does not work on aftermarket modules, however. The car will run when started, but, if the tester is used, there will be no spark at all...then you know you have an aftermarket module. If you don't have the tester, then you can use a meter and check the resistance across each coil pack (between the two plug wire terminals on a given coil pack) when it is hot from running. The resistance should fall between 11-13,000 ohms on a good Type I coil pack. Type I is the original coil used on our cars...one piece unit with three individual coils molded into it. This is only a test of the coil packs and not the module and is probably about 85% reliable. Sometimes a coil will pass this resistance test but still fail under boost. The best test outside the Casper's tester is to swap a known good coil and module onto the car. I have never seen one that failed the resistance test to be anything but bad.
If the scan tool is reporting timing retard, detonation may be causing the problem, but, typically, this will not be as severe as a bad coil or module and the symptoms will not be as obvious.
At times, a loose balancer, or misadjusted crank sensor can cause an obvious miss at higher rpm. It is always a good idea to check the crank sensor for proper clearance on all three blades of the damper and to check the damper for wobble or movement when the engine is revved up.
A bad cam sensor can also cause a problem. Sometimes this becomes obvious after the car has been driven awhile. If the cam sensor has been out of the car and reinstalled, be sure it was properly installed and not on the edge of the window, or 180 degrees out. Sometimes, unplugging the cam sensor after the car is running will cause the car to run better. This is normally a sign of some problem with the sensor.
See the note in the next section about the cam sensor-
