My pontiac grand prix has a multi cylinder misfire according to my checker not sure of cause also does not want to shift proper . car seems ok at normal acceleration acts up on agressive accel any ideas appreciated. replaced the plugs allready , burnt out no change. the car has a 3800 engine not supercharged thanks
2007-09-29 06:21:18 · 3 answers · asked by dr car g 2 in Cars & Transportation ➔ Car Makes ➔ Pontiac
I can offer a few ideas on this, first is there could be a burned through intake allowing coolant intrusion into the engine. Have you checked the coolant level? Have you had to add coolant recently? Second thought would be a bad coil. If your checker will give you info, see what cylinders the majority of the misfires are on and then see if they match one of your coils. (Each coil fires two cylinders). If you cant read this data with your checker, mark the plug wires so you know where they go, disconnect them all at the coils and have a friend crank the engine over briefly while you watch the spark. If the coils are good they will have spark jumping from one coil terminal to the other on each coil. A weak coil (or a bad ignition module) won't have spark jumping back and forth. If you find one that spark is not jumping like it should, before you buy a coil swap the coil that is not jumping good with one that is. Then crank it over again and see if the "bad coil" is still "bad". If it now fires but the one you swapped it with doesn't, then you have a bad ignition module. Third thing would be a plugged cat. converter. You would need a backpressure gage to properly test this but it's not uncommon, and they will shift weird under hard accel. One thing you could do would be remove the O2 sensor and with it out drive the car under hard accel, but you would have to be very carefull as hot exhaust will come out of the hole where the sensor was and could burn anything it hits so I really don't recommend doing this unless you absolutly have to! Plus you could set a trouble code that will turn on your check engine light.
Hope this helps, good luck!
2007-09-29 11:41:51 · answer #1 · answered by Ham_Samich 2 · 1⤊ 0⤋
I would suspect the spark plug wires. My 1997 GTP did good until I replace the spark plugs then the wires started to short to ground. Any good quality wire will work But the correct leingth AC delco wires is what I went with.
2007-09-29 15:00:50 · answer #2 · answered by John Paul 7 · 1⤊ 0⤋
CHECK THE IGNITION WIRES AS WELL AS THE COIL PACK.
IF THEY ARE OKAY YOU COULD ALSO HAVE BAD INJECTORS.
SOME VEHICLES THAT HAVE A MULTI OR RANDOM CYLINDER MISS-FIRE ARE VERY HARD TO PINPOINT QUICKLY.
2007-10-03 09:37:57 · answer #3 · answered by Anonymous · 0⤊ 0⤋