Cylinder 5 misfire+ others

Dbane2020

New Member
Apr 9, 2020
6
0
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36
Roanoke Virginia
I have a 1998 Mustang GT had it in and out of the shop and they dont know what is wrong with it. It has a check engine light on for P0305 cylinder 5 misfire and that is all. The car has a slight miss when it gets warm in 3rd 4th and 5th when I try and stay a certain speed but only under light throttle5-10%. Half to full throttle and the car is fine. Other than that the car runs great. I've replaced spark plugs, coil packs, wires, fuel filter, and throttle position sensor all with oem. My mechanic checked to make sure it was getting spark and also checked the injectors and swapped them around also checking fuel pressure and made sure all had correct voltage and resistance. Except the plugs kenne bell suggested copper plugs. Car has a 2.1 kenne bell kit on it. Any help would be greatly appreciated. Because I am stumped.
 
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MustangIIMatt

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I have a 1998 Mustang GT had it in and out of the shop and they dont know what is wrong with it. It has a check engine light on for P0305 cylinder 5 misfire and that is all. The car has a slight miss when it gets warm in 3rd 4th and 5th when I try and stay a certain speed but only under light throttle5-10%. Half to full throttle and the car is fine. Other than that the car runs great. I've replaced spark plugs, coil packs, wires, fuel filter, and throttle position sensor all with oem. My mechanic checked to make sure it was getting spark and also checked the injectors and swapped them around also checking fuel pressure and made sure all had correct voltage and resistance. Except the plugs kenne bell suggested copper plugs. Car has a 2.1 kenne bell kit on it. Any help would be greatly appreciated. Because I am stumped.
Have them run a compression test, and if cylinder 5 fails the test, have them run a cylinder leakdown test.
 

Dbane2020

New Member
Apr 9, 2020
6
0
1
36
Roanoke Virginia
Just to follow up. I spoke to the tech guys at kenne bell and they informed me that the hesitation or slight miss at idle and when cruising at any set speed is caused by the bypass valve on my supercharger being over the intake manifold on cylinder 5 causing a lean condition. The fix is an injector modified by them.