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Fuel trims off, can't find vacuum leak
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filschaos
New User
Mar 13, 2009, 11:35 AM
Post #1 of 2
(1048 views)
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Fuel trims off, can't find vacuum leak
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I have '98 Grand Prix GTP. My cars check engine light is on for fuel trims being off. I also some power loss, not much, and my average MPG is down by a couple miles. Idle speed sounds fine, sounds fine under power.
Heater gate doesn't close all the way so it blows out all directions regardless of where you set it.
Last week: I tore down to the intake manifold while fixing an oil leak and replace all gaskets on the way out, followed all directions and torqs exactly. I replace the plugs while I was at it. Check engine light popped back on next day, engine started mis-firing. Took it in they said vacuuum leak was somewhere in the block and they re-did from the intake manifold gaskets up... again. They also said new plugs were already bad from heat causing the mis-fire, and replaced them. Running better now, no engine misfire, but my check engine light is still on and all other issues are the same. I have gone through and replaced and triple checked every vacuum line and connection, and zip tied all of them down.
So now: I have emptied my emergency fund trying to get this fixed, I'm afraid to take it back to the repair shop I use since they didn't fix it the first time. I can try a dealer if I have to, but don't want to get screwed on price. Is this actually a vacuum leak or is there something else that can have these symptons? As far as I understand the vacuum diagram, the only things I havn't replaced yet are the sensors it runs through. Help ideas?
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Loren Champlain Sr
Veteran
/ Moderator
Mar 13, 2009, 3:29 PM
Post #2 of 2
(1042 views)
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Re: Fuel trims off, can't find vacuum leak
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Since you mentioned vacuum leaks, I'll assume that you are having a lean condition. Oxygen sensors, fuel pressure, plugged fuel filter, ect. will cause lean conditions. Since it's a '98, the ECM should store misfire and O2 codes. If you are lacking fuel, via weak pump or clogged filter, you'll see that in the fuel trims, but generally won't set a code other than lean, bank one and/or lean, bank two. Keep in mind, the O2 sensors are telling you what they are seeing...not necessarily the cause.
Loren
SW Washington
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