I have a 00' GT. I brought it out this spring and it all of a sudden had a mis that was not there when I put it away. It mostly occurs when there is a load on the engine, pulling out on a grade or just gettin on it. It does go away after 2500-3000 RPM. I must also add that it gets worse as the temp goes up. I have changed the plugs and fuel filter. I have unpluged the coils one at a time while it was running and they all reacted the same. I did get one new injector, I swaped it out on the first two but that is as far as I got. I cleaned the Mass Air Sensor. Any other ideas?
miss in the engine
- Thread starter jmckellar
- Start date
wmburns
SN Certified Technician
When a problem developes after a prolonged storage, my first thought is "stale gas" or water in the gas. Have you done anything to combat "skunky gas"?
Are there any Check engine DTC codes? Any blinking check engine lights? If so, please post the full codes. Most any local autoparts store will read the codes for free.
How did you clean the MAF? The MAF is easily damaged by harsh cleaners. Clean with a product that does not leave a residue.
The post states the misfire goes away above 2500 RPM's. One possibility that comes to mind is excessive EGR flow.
A vacuum leak can also cause the symptom listed. Note, even a tiny vacuum leak can cause problems. This can not be over emphasized.
Partially clogged injectors are another possibility (poor low flow spray pattern). Confirm that the fuel pressure reference line is connected and leak free.
Do you have an ODB2 scanner?
FWIIW, do not disconnect the COP while the motor is running. This will generate a continious misfire with the full unburnt fuel charge going straight into the exhaust. Once in the Cats, it will flare and overheat the cats.
If an injector problem is suspected, consider an injector cleaning/flow testing service such as injectorrx.com. Cheaper than new. Once tested, the injectors are as good as new.
Are there any Check engine DTC codes? Any blinking check engine lights? If so, please post the full codes. Most any local autoparts store will read the codes for free.
How did you clean the MAF? The MAF is easily damaged by harsh cleaners. Clean with a product that does not leave a residue.
The post states the misfire goes away above 2500 RPM's. One possibility that comes to mind is excessive EGR flow.
A vacuum leak can also cause the symptom listed. Note, even a tiny vacuum leak can cause problems. This can not be over emphasized.
Partially clogged injectors are another possibility (poor low flow spray pattern). Confirm that the fuel pressure reference line is connected and leak free.
Do you have an ODB2 scanner?
FWIIW, do not disconnect the COP while the motor is running. This will generate a continious misfire with the full unburnt fuel charge going straight into the exhaust. Once in the Cats, it will flare and overheat the cats.
If an injector problem is suspected, consider an injector cleaning/flow testing service such as injectorrx.com. Cheaper than new. Once tested, the injectors are as good as new.
Well, I have switched out the four injectors on the right side all without any change. I went to the other side, being that it is more involved I took out all four injectors and inspected them to see if I could notice anything obvious. None of them were any worse than the others, so I just replaced the first one. What did I find, my problem got worse. Good news in a way. I guess it tells me that I have a fuel problem for sure. I went ahead and put back in the original injector. That is were I left it.
Rejekt
Member
wmburns
SN Certified Technician
Re-consider having the injectors cleaned and flow tested. It is obvious that at least one injector is not pulling its weight. A visual inspection is not the best way to determine a bad injector. For less than the cost of 4 new injectors, all 8 could have been tested.
Do you have underdrive pulleys? Some styles of underdrive pulleys will cause an unstable CKP sensor signal. The problem is worse if the damper bolt has been incorrectly torqued.
What about all of the other suggestions?
wmburns
SN Certified Technician
If I understand the post, you have 4 new injectors. Consider having just the 4 old injectors tested.
This would allow you to continue to drive the car while waiting. When the cleaned injectors came back, then use them in place of the remaining injectors.
This would allow you to continue to drive the car while waiting. When the cleaned injectors came back, then use them in place of the remaining injectors.
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