Hey everyone im new to the site i had got a nice 98 gtp for $800 with 130000 miles on it... Drove fine un till i stomped on it on the highway one day then is started to missfire i changed the plugs and wires drives good but it only missfired when you pushed it so i had it scaned it said crank postion sensor so i changed that also still the same thing i also changed the fuel filter still missfires only when you push it any ideas??
Missing when pushing the car?
- Thread starter john954
- Start date
Scottydoggs
Killa Bee
icm or a coil pack. maybe, or maybe even a injector.
is the cel flashing when this happens? (check engine light) usually because of multiple misfires or a clogged cat.
is the cel flashing when this happens? (check engine light) usually because of multiple misfires or a clogged cat.
Scottydoggs
Killa Bee
your having either very bad random misfires or a clogged cat.
does the car feel rather gut less? then the cat could be clogged. or at night after driving it for a while look under the car and see if the cat is glowing red, if so its clogged, you can also when the cars cold, hit the cat with your hand hard, listen for crap rattling around inside the cat. if so its shot.
and stop getting on it hard enough to make it flash, that flashing is telling you that a catastrophic event is happening.
and re scan the car, see if you have stored codes.
does the car feel rather gut less? then the cat could be clogged. or at night after driving it for a while look under the car and see if the cat is glowing red, if so its clogged, you can also when the cars cold, hit the cat with your hand hard, listen for crap rattling around inside the cat. if so its shot.
and stop getting on it hard enough to make it flash, that flashing is telling you that a catastrophic event is happening.
and re scan the car, see if you have stored codes.
nukkinfuttz
New member
when your car goes into boost, the coils must product MORE voltage than when N/A to be able to jump the spark gap in a higher pressure. This puts the coils under a higher load which they may or may not be able to handle. If they cannot, then you just get no spark, and you will experience a misfire under load only. When your just crusing, the throttle body is nearly closed, so you dont have alot of air actually entering the cylinder, so the peak pressures at not nearly as high. without as much air pressure in there, the coils dont have to create as much voltage to jump the gap, its like a walk in the park.
This same symptom can also happen if your plugs are gapped too big. It will be okay at normal driving but experience "blow out" under boost. Make sure your plugs are gapped to the proper spec first, if that isnt it, I'd try a new coil pack.
This same symptom can also happen if your plugs are gapped too big. It will be okay at normal driving but experience "blow out" under boost. Make sure your plugs are gapped to the proper spec first, if that isnt it, I'd try a new coil pack.
Last edited:
nukkinfuttz
New member
Sorry, I cant leave well enough alone...
To jump a gap, the there is a certain required voltage you must achieve PER INCH OF GAP AT ONE STANDARD ATMOSPHERE! Look at that really close and see all the moving parts. Bacially, anything you do that puts more air molecules in the "gap" will require more voltage to create an arc. So, for instance, if you had your spark plug in a slight vacumm, you would need less voltage to jump the gap than if it were in 10PSI of pressure. the more PSI of pressure would in effect put more air molecules in the gap, which would require more voltage to overcome and produce an arc. Likewise, if you were to hold the pressure constant but increase the gap distance by adjusting the electrode, you would also be putting more air molecules in the gap, which would require more voltage be produced by the coil to create an arc.
So, to achieve a proper spark, you must have a coil that can produce more voltage than the boost pressure and plug gap could ever require. If you get blow out, then you must reduce boost pressure or spark gap, or switch to a more powerful coil that can create more voltage.
see how that all works now? That is why a coil that misfires under load would be just fine and dandy during normal driving.
thank you have a nice day.
To jump a gap, the there is a certain required voltage you must achieve PER INCH OF GAP AT ONE STANDARD ATMOSPHERE! Look at that really close and see all the moving parts. Bacially, anything you do that puts more air molecules in the "gap" will require more voltage to create an arc. So, for instance, if you had your spark plug in a slight vacumm, you would need less voltage to jump the gap than if it were in 10PSI of pressure. the more PSI of pressure would in effect put more air molecules in the gap, which would require more voltage to overcome and produce an arc. Likewise, if you were to hold the pressure constant but increase the gap distance by adjusting the electrode, you would also be putting more air molecules in the gap, which would require more voltage be produced by the coil to create an arc.
So, to achieve a proper spark, you must have a coil that can produce more voltage than the boost pressure and plug gap could ever require. If you get blow out, then you must reduce boost pressure or spark gap, or switch to a more powerful coil that can create more voltage.
see how that all works now? That is why a coil that misfires under load would be just fine and dandy during normal driving.
thank you have a nice day.
Scottydoggs
Killa Bee
you can start by one by one swapping parts around, swap the plug wire, if no change, swap the spark plug. if no change, swap the coil around, if no change swap the injector. this is to see if the misfire moves. if the misfire moves you found your problem part.
like a said one at a time, test it out, on to the next one.
like a said one at a time, test it out, on to the next one.
