Is my fuel pressure too high?
Is my fuel pressure too high? I'll try this again I guess, no replies in the fueling forum except from someone who apparently didn't read what I posted.
I have an ex drag car turned stock, it's a 2001 Z28. It has a Racetronics fuel pump and relay, and just gutted cats, air lid.
It's an A4 car and tends to idle low when coming to a stop.
I checked the pressure today and it's 64 psi at idle.
My 2002 SS stock pump is 58 psi at idle.
Is running at 64 psi going to cause any problems?
I have HPTuners if anything can be changed with that.
I have an ex drag car turned stock, it's a 2001 Z28. It has a Racetronics fuel pump and relay, and just gutted cats, air lid.
It's an A4 car and tends to idle low when coming to a stop.
I checked the pressure today and it's 64 psi at idle.
My 2002 SS stock pump is 58 psi at idle.
Is running at 64 psi going to cause any problems?
I have HPTuners if anything can be changed with that.
FWIW I just put this stock engine in and seafoamed it three times, cleaned the TB (removed the sensors first and cleaned only the end of the IAC)
Not sure about the fuel pressure, but my car was doing that (low idle while stopping, around 500 rpm) but would act fine when stopped, most of the time it would act fine. Anyway, the problem for me was my o2 wires under the car were too low and water would get on the connectors AND they were sitting on the collectors and almost melted through the wiring. After adjusting the wiring the car runs like a champ and I dont have that problem anymore. Hope that helps.
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TECH Addict
Joined: Jun 2005
Posts: 2,660
Likes: 14
From: England
I doubt it will be an issue. The injection system should be able to supply to correct fuelling. Are you running stock injectors?
As for the idle issue, well from what you've listed the descreened MAF screams as the most likely candidate, either that or something in the tune.
While I'm sure the screen may affect flow slightly it is also there to greate a laminar air flow for the MAF to make a more accurate reading. If the idle is not causing it to stall or any real issues I probably wouldn't worry too much at present, just keep and eye out for any changes.
As for the idle issue, well from what you've listed the descreened MAF screams as the most likely candidate, either that or something in the tune.
While I'm sure the screen may affect flow slightly it is also there to greate a laminar air flow for the MAF to make a more accurate reading. If the idle is not causing it to stall or any real issues I probably wouldn't worry too much at present, just keep and eye out for any changes.
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OK, I hooked up HPTuners today to adjust the idle cracker setting, and I logged a run.
With the descreened MAF it idles better, but I noticed all the fuel trims rarely if ever come out of the negative, while decelerating they even hit -43 once. The average is -10.
I found it kind of weird that it changes drastically when put in gear.
So I took the whole lid and all off my SS (same type SLP lid and stock screened MAF) and test drove it. All the fuel trims stay within +5 to -5. It idles perfect too.
Then I took that off and put on a spare MAF with a screen, it was in between the two. It was rare that it ever went positive. But the negatives weren't so low, around -8.
Any idea what the hells going on?
Is it the lack of a screen or two bad sensors vs one good one?
With the descreened MAF it idles better, but I noticed all the fuel trims rarely if ever come out of the negative, while decelerating they even hit -43 once. The average is -10.
I found it kind of weird that it changes drastically when put in gear.
So I took the whole lid and all off my SS (same type SLP lid and stock screened MAF) and test drove it. All the fuel trims stay within +5 to -5. It idles perfect too.
Then I took that off and put on a spare MAF with a screen, it was in between the two. It was rare that it ever went positive. But the negatives weren't so low, around -8.
Any idea what the hells going on?
Is it the lack of a screen or two bad sensors vs one good one?
Filter is new. The idle cracker seemed to solve the problem, well I did put a screened maf back in also.
Now my concern is the fuel trims. I ran it a good while, even reset the trims but that didn't seem to change much.
What it's doing now is the LTFT's NEVER go positive, MAYBE +1 but no more, they usually run as low as -10.8
The STFT's run from around +3 to -3 back and fourth pretty quick.
And they hit 0 at wot, the narrow band O2's read around 930 at wot.
All that tuning is untouched.
It's stock with a screened and properly cleaned MAF, paper filter, SLP lid, no AIR, gutted cats.
82,000 miles. It runs ok, in fact I wouldn't think there was a problem if I didn't look at the fuel trims.
Now my concern is the fuel trims. I ran it a good while, even reset the trims but that didn't seem to change much.
What it's doing now is the LTFT's NEVER go positive, MAYBE +1 but no more, they usually run as low as -10.8
The STFT's run from around +3 to -3 back and fourth pretty quick.
And they hit 0 at wot, the narrow band O2's read around 930 at wot.
All that tuning is untouched.
It's stock with a screened and properly cleaned MAF, paper filter, SLP lid, no AIR, gutted cats.
82,000 miles. It runs ok, in fact I wouldn't think there was a problem if I didn't look at the fuel trims.
Registered User
Joined: May 2008
Posts: 47
Likes: 0
From: Sandston, VA
Stock fuel pressure with key on engine off should be between 55-62lbs. Does your fuel pressure change with the regulator disconnected? I've seen some wierd fuel trims caused by only a pound of high fuel pressure. Any codes for rich condition?
No codes for a rich condition.
It gets 64 psi fuel pressure at idle, it has a Racetronics fuel pump and wiring kit, this was already on the car when I bought it as a roller. Racetronics said it would be ok to leave this on a stock engine.
It gets 64 psi fuel pressure at idle, it has a Racetronics fuel pump and wiring kit, this was already on the car when I bought it as a roller. Racetronics said it would be ok to leave this on a stock engine.
Registered User
Joined: May 2008
Posts: 47
Likes: 0
From: Sandston, VA
When I said disconnect, I meant pull the vacuum hose off the regulator. But then I forgot that there is no vacuum hose at the regulator. So now my dumb *** will take a walk of shame after a swift kick in the sack.