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Old 10-29-2012, 03:07 PM   #1
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Fuel system or ecu

Ok, I'm having trouble with the car acting like its leaning or choking out. I have a code saying it ran at lean limit then running open loop. I tested my fuel pressure and am running 30lbs at idle. My chilton book says that I should have 45+lbs at idle, so I replaced the fuel filter and fuel pump and still have the same pressure. If I unhook the pressure regulator vacuum line, I jump to approximately 43lbs. I read that the ecu controls the fuel pump flow, so I wander if the po had a bad tune in the car, or if something else is the issue. My car is a 98 Gt 4.6l 16v
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Old 10-29-2012, 03:39 PM   #2
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My Cobra has a "lean limit" code when I bought it... and acted like it had a vacuum leak...

Check your IAC... It's on the Throttle Body. I changed mine and the car ran great afterwards...

If your car is running, and you unplug the IAC... the car should die. If it doesn't do anything when you unplug the IAC, you may have a bad one.
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Old 10-29-2012, 04:10 PM   #3
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Quote:
Originally Posted by bmabbott
My Cobra has a "lean limit" code when I bought it... and acted like it had a vacuum leak...

Check your IAC... It's on the Throttle Body. I changed mine and the car ran great afterwards...

If your car is running, and you unplug the IAC... the car should die. If it doesn't do anything when you unplug the IAC, you may have a bad one.
I have a recent receipt from where the po replace the iac. My car dies immediately if I unplug it too lol. I talked to the shealership and they want $65 to flash a default tune to it so I think I might do that.
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Old 10-29-2012, 09:59 PM   #4
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What is the code? 30 psi at idle, if you checked the actual fuel rail pressure, is normal because of the way the return-less fuel system works...
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Old 10-29-2012, 10:20 PM   #5
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I screwed my pressure gauge in at the Schader valve on the fuel rail.

---------- Post added at 10:20 PM ---------- Previous post was at 10:19 PM ----------

Quote:
Originally Posted by Cmrtopher
I screwed my pressure gauge in at the Schader valve on the fuel rail.
Also, it's got p1151 p1150 and a couple of others I can't remember.
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Old 10-29-2012, 11:08 PM   #6
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I had that problem to on my 96 and I wanna say I had to replace somethin on the return side but I can't remember what it was, its been a few years back
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Old 10-30-2012, 06:54 AM   #7
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Quote:
Originally Posted by Cmrtopher View Post
I screwed my pressure gauge in at the Schader valve on the fuel rail.

---------- Post added at 10:20 PM ---------- Previous post was at 10:19 PM ----------



Also, it's got p1151 p1150 and a couple of others I can't remember.
Those both indicate (click here) that the driver's side O² sensor is reporting a lean condition, not necessarily that the mix is lean--a bad O² sensor generates no output voltage, which the PCM interprets as the mix being lean. The PCM then tries to make the AFR richer, when it has made it more than 25% richer and the sensor still says it's lean (and the engine is running like crap) it throws the DTCs you observed.

That the f/p went up to 43 psi with the vacuum line disconnected indicates the fuel pressure regulator is doing what it should. Also, as the problem seems to be affecting just one bank it is unlikely the cause would be something that should affect both banks--like fuel pressure.

You can bench test the O² sensor using a propane torch and multimeter.
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