Mechanics help on fuel pressure!
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Mechanics help on fuel pressure!
My 86E vette is running pretty rich. Fuel pressure is around 42 psi with 24# injectors. The engine is stock with deleted precats, hollow cat, Dynomax mufflers, open lid K&N, and a worthless airfoil. There are no codes and idle surges up and down until closed loop. With the 24lb injectors and being on the high side of fuel pressure would it do justice to get a AFPR to lower the fuel pressure so it wouldn't burn rich? Thanks
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by Z~max
Once the car is in closed loop the O2 sensor controls the AFR,
Originally Posted by Z~max
so any change made in open loop would be defeated in closed loop.
Not necessarily. The car runs rich in open and closed. Pessure stay the same no matter what loop I'm in. ECM has no control over pressure and the O2 sensor sends a signal of .1v lean to .9v rich. I have not had a scan done to see what my BLM's are or to see what my O2 sensor is sending, but just wondering if a lower pressure (say 36) would benefit me. With bigger than stock injectors I will eventually need a chip burned to compensate. I have done a Field Service mode check and the only time my ECM sees a rich mixture is when giving throttle and comming off throttle.
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Well in open loop is when the car idles up and down, still trying to figure this one out. In closed loop it idles pretty good. The rich condition exist in both. With the larger injectors and the high side fuel pressure I was just wondering if lowering the pressure would give any benefit to the rich exhaust. I have a different ECM and am going to change it out and see if there is a difference. I am going to get a scan and probably get my chip burned accordingly.
Advanced
Joined: May 2006
Posts: 67
Likes: 0
From: Valencia PA
I would look for a sensor that is out of range. It my still be in range according to the computer, but it may not be accurate. A temp. sensor reading at -20* when it is really 70*. Are you getting a check engine light? If you are I would start there.
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Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by RRT vette
My 86E vette is running pretty rich. Fuel pressure is around 42 psi with 24# injectors. The engine is stock with deleted precats, hollow cat, Dynomax mufflers, open lid K&N, and a worthless airfoil. There are no codes and idle surges up and down until closed loop. With the 24lb injectors and being on the high side of fuel pressure would it do justice to get a AFPR to lower the fuel pressure so it wouldn't burn rich? Thanks
This might give a little better understanding of my problem.
http://forums.corvetteforum.com/show....php?t=1380382
Last edited by RRT vette; May 15, 2006 at 12:39 AM.
Team Owner
Joined: Jan 2003
Posts: 20,333
Likes: 262
From: Summerland B.C. Canada
I would think an adjustable FPR would help you with your rich condition. Lowering the pressure will reduce the amount of fuel during open loop and the ECM will just re-learn for closed loop. Looks good on paper.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
with Agent86 on the AFPR. On the other hand, I don't think your injectors are what's causing the surging during open loop....but your unknown chip...is exactly that, and an unknown is always hard to deal with.OH, BTW,did you read the post "adjusted tps, but I'm wondering"
http://forums.corvetteforum.com/show....php?t=1389867
Seems we all may have missed a step here-
Last edited by rick lambert; May 15, 2006 at 10:07 AM.
Thread Starter
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Yes Rick, I read this thread and have heard of doing this but I didn't when I set my TPS. I will give it a try. BTW I was just wanting some opinions on the AFPR before buying one. If it's worth the money, I will go ahead and do it. There's nothing wrong with the stocker I have now.