stumped over engine misfire
#1
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This is a recurring problem I have had ever since I bought the car. Once the car is warmed up I'll stop for 40 minutes or so. When I start up again it misfires. Codes show multiple misfires all eight cylinders. This goes for 20 seconds or so and then it smooths out and runs fine. The check engine light comes on but it doesn't go into restricted performance mode. Tried BG throttle body cleaning, SeaFoam, new plugs, new fuel filter. No codes except the misfire. I'm stumped, my mechanic is stumped. Anybody else had this happen. BTW, this only happens when the engine is warmed up. Cold starts are fine.
#2
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This is a recurring problem I have had ever since I bought the car. Once the car is warmed up I'll stop for 40 minutes or so. When I start up again it misfires. Codes show multiple misfires all eight cylinders. This goes for 20 seconds or so and then it smooths out and runs fine. The check engine light comes on but it doesn't go into restricted performance mode. Tried BG throttle body cleaning, SeaFoam, new plugs, new fuel filter. No codes except the misfire. I'm stumped, my mechanic is stumped. Anybody else had this happen. BTW, this only happens when the engine is warmed up. Cold starts are fine.
Cheers, Jarle
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#6
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Mechanic doesn't think it's O2 sensors since it only happens at start when engine is warm and no miss detected after the first few seconds. He thinks an injector is leaking fuel into cylinder after car is shut off. Then if the car is started again before fuel dissipates, I get the multiple misfires. He said to try another can of SeaFoam and see if that makes a difference.
#7
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Location: Damon /Houston, Texas
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Are your heat shields still on over and around the cats? Especially the drivers side were the fuel lines come up from under the car and around them. If not or even if they are, you may be experiancing good old fashion heat soak of the fuel in the lines and partial vaporization.
Also try to find fuel without ethanol, i know its almost impossible around large cities, but we see alot of ethanol induced starting issues
Also try to find fuel without ethanol, i know its almost impossible around large cities, but we see alot of ethanol induced starting issues
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Its minimized with higher fuel pressure used in fuel injection systems. But when the fuel sits and it over hi temp items like the cats, it can cause partial vaporization which can lead to stumbling when the vapor hits the injectors at startup. There are alot of insulation materials and wraps to allieviate this issue. I know ethanol is a way of life nowadays, but we see issues with it and many times when tested can find more than 10% in the tank. We are also finding whitish flakes or deposits on the injector tips from ethanol. This may have nothing to do with your issue, but a possibilty
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#16
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you can check by hooking up a fuel pressure gauge to the fuel rail and watch what happens after you drive and then stop and let it sit. Tape it to the windshield and drive around withit and see what happens. if it bleeds down the only way to know which 1 is to remove the injectors and send them out to be tested and cleaned. If you have 1 or more that cannot be repaired and cleaned to work properly then you need to replace those.
I would recommend injectorrx.com here in Houston
http://injectorrx.com/
#17
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This is a recurring problem I have had ever since I bought the car. Once the car is warmed up I'll stop for 40 minutes or so. When I start up again it misfires. Codes show multiple misfires all eight cylinders. This goes for 20 seconds or so and then it smooths out and runs fine. The check engine light comes on but it doesn't go into restricted performance mode. Tried BG throttle body cleaning, SeaFoam, new plugs, new fuel filter. No codes except the misfire. I'm stumped, my mechanic is stumped. Anybody else had this happen. BTW, this only happens when the engine is warmed up. Cold starts are fine.
#18
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I reread your post and forgot the car ran normal after the misfiring, forget the air leak. It is probably fuel vaporization although I have rarely heard of it on these cars, or any fuel injected car for that matter, since the fuel return system keeps the fuel cool. The 4.2 cars do not have a fuel return system so I guess they use a different method of preventing vaporization, probably the high pressure of their system (70 psi instead of 42 psi in the 4.0).
#19
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But this should show as a lean engine condition since it is air going in the engine the mass air flow sensor is not reading. Like when the air intake tube bellows deteriorate and start cracking apart you get p0171, p0174
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