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Misfires in 3 cylinders
1996 Camaro Convertible Base 3.8L
OK not sure why but I am getting a lot of misfires in # 1 & 2 with more in #6 intermittently. I've changed the wires, coils and plugs. Not sure why its just these unless its the injectors. Never changed and injector though. Any other thoughts? |
It can be a lot of things. ICM is the first thing that comes to mind but it could be anything that leans the cylinders out. Even a bad MAF sensor, sticking EGR vacuum leak. How do the plugs look?
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the old plugs should tell you something, do you still have them?
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Don't have the old plugs they were changed about a month ago, this is a new issue. Already changed the EGR also. It's consistently those 3 cylinders I would think if it were a sensor it would effect all the cylinders randomly, no?
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Ok checked a few more things. Fuel pressure is good and steady at 43psi while running. Listened to injectors with stethoscope and they all sound fine. So could still be a clogged injector or 2 but I'm starting to lean towards a vacuum leak somewhere on the intake manifold. That would explain the 2 front cylinders misfiring. Gonna try some starter fluid tomorrow.
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Ok problem solved!!! Feel like I hit the lottery today. Wanted to post this to help others who may end up with same problem. I noticed when checking the fuel pressure that unless the car was running the pressure dropped quickly. One of the tests was to cycle the ignition 2 or 3 times without starting the car and see if it holds pressure and it didn't at all. I disconnected the vacuum hose to the fuel pressure regulator and a lot of gas came out. So that would explain the vacuum leak as it was sucking fuel in to the vacuum system and also the long cranking when starting. That was a bear to replace. I was hoping it might fix the misfire also and it did! Car fires right up now and drove it around town with computer plugged in and didn't get a single misfire, also long term fuel trim was right around 2-3% the whole time. Runs smooth now and I'm sure the mileage will go way up as the LTFT was around 25% before. Thanks everyone for all the help!!!!
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really weird that it was only missing on those cylinders
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I'm thinking that it was those cylinders because #1 and #2 are at the ends of the fuel rails so they were loosing the most pressure.
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Nice work figuring that out!
Thanks for posting the solution, HAPPY DRIVING!! |
Originally Posted by subysti
(Post 695511)
Ok problem solved!!! Feel like I hit the lottery today. Wanted to post this to help others who may end up with same problem. I noticed when checking the fuel pressure that unless the car was running the pressure dropped quickly. One of the tests was to cycle the ignition 2 or 3 times without starting the car and see if it holds pressure and it didn't at all. I disconnected the vacuum hose to the fuel pressure regulator and a lot of gas came out. So that would explain the vacuum leak as it was sucking fuel in to the vacuum system and also the long cranking when starting. That was a bear to replace. I was hoping it might fix the misfire also and it did! Car fires right up now and drove it around town with computer plugged in and didn't get a single misfire, also long term fuel trim was right around 2-3% the whole time. Runs smooth now and I'm sure the mileage will go way up as the LTFT was around 25% before. Thanks everyone for all the help!!!!
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