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Old 02-23-2010, 11:41 AM   #1
patrick smith
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Default Bad idle after fuel pump install??

I installed my new walbro 255 fuel pump, and now at idle my rpms drop to 100 almost to stall, then they come back up to 550 ish. Not sure why. My AFR is showing at idle its running richer than it did before the install. The install went fine on the FP, nothing broke it all went in perfect. After the install I unplugged the neg terminal of the battery, then let it sit for 5-10 minutes, no codes seemed perfect. Anyone else have this problem, did some searching and nada. Im running a tuned stage 2 map from HB, and once I get going the car runs fine, its just at idol. Went to boost and did a pretty hard 3rd gear pull and no issues, just at idol. Thoughts?


once i remove the neg battery terminal do i need to reload my tune map?

Patrick
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Last edited by patrick smith; 02-23-2010 at 05:54 PM.
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Old 02-23-2010, 11:52 AM   #2
the suicidal eggroll
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Since you have a custom tune, it could be that your old pump was failing, and the tuner took care of it with the MAF scaling. Now with the working pump you're running rich.

Another option is your FPR is going out and can't bypass enough fuel to keep the pressure down at idle with the 255. A fuel pressure gauge would tell you if that's the case.

Another option is your MAF scaling or injector latency is bad, your car had previously corrected for it with the long term fuel trims, and since you reset the ECU it's going to take the car a day or 2 to re-learn the trims and bring you back to 14.7 at idle.
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Old 02-23-2010, 11:54 AM   #3
GrimmSpeed
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No, you should not have to reload your map after removing the negative terminal. A tune actually reflashes your ECU so something like cutting power should not change this.

will
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Old 02-23-2010, 12:02 PM   #4
patrick smith
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Quote:
Originally Posted by the suicidal eggroll View Post
Since you have a custom tune, it could be that your old pump was failing, and the tuner took care of it with the MAF scaling. Now with the working pump you're running rich.

Another option is your FPR is going out and can't bypass enough fuel to keep the pressure down at idle with the 255. A fuel pressure gauge would tell you if that's the case.

Another option is your MAF scaling or injector latency is bad, your car had previously corrected for it with the long term fuel trims, and since you reset the ECU it's going to take the car a day or 2 to re-learn the trims and bring you back to 14.7 at idle.
this is what i was thinking and a friend told me also. ill run it for a few days and see if it fixes. i have not really run it after the install.

thanks
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Old 02-23-2010, 03:00 PM   #5
Team K Productions
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.nm...
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Old 02-23-2010, 05:55 PM   #6
patrick smith
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UPDATE
took it out for a few miles of running and the idle seems better now. still not perfect, but im going in for a retune, that should be the way to go. but after driving it around for a few hours seems to be ok now. i guess the ecu needed to learn the new fuel pressure.

Last edited by patrick smith; 02-23-2010 at 09:26 PM.
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Old 02-23-2010, 06:55 PM   #7
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I was going to say to ask Jon what he thought it might be.
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