Car running extremely lean...
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From: Englewood, CO
Car running extremely lean... I posted this in tuning and diagnostics, probably not the right place, so i will put it here.
Allright, heres what happened. i just got nitrous for my car a while back. I just went to the dyno to see what the car would do. I mainly wanted to get a feel for the AFR because i dont have a guage right now. Long story short, we strapped it down, and ran a baseline NA, and the car was at 18:1 the WHOLE RPM band. we thought it was his sensors, so he put on some new ones, and it was the same thing. tried them out on a pickup, and they read fine. so my car is definitely reading that lean, and i dont know why. i have TSP's 233/239 cam, headers, ORY. I also have a mail order tune from them. The last time i dynoed my car it ran around 370hp without a dyno tune, which wasnt that bad. but now im running lean and cranking out a whopping 277hp. What could be the problem here? we checked the fuel pressure and it was around 58-62 psi. but the car is still extremely lean. any suggestions? has this happened to anyone else?
Allright, heres what happened. i just got nitrous for my car a while back. I just went to the dyno to see what the car would do. I mainly wanted to get a feel for the AFR because i dont have a guage right now. Long story short, we strapped it down, and ran a baseline NA, and the car was at 18:1 the WHOLE RPM band. we thought it was his sensors, so he put on some new ones, and it was the same thing. tried them out on a pickup, and they read fine. so my car is definitely reading that lean, and i dont know why. i have TSP's 233/239 cam, headers, ORY. I also have a mail order tune from them. The last time i dynoed my car it ran around 370hp without a dyno tune, which wasnt that bad. but now im running lean and cranking out a whopping 277hp. What could be the problem here? we checked the fuel pressure and it was around 58-62 psi. but the car is still extremely lean. any suggestions? has this happened to anyone else?
you are lucky that thing held up.. You didn't try the spray out before or after this did you?
There isn't much info here though...
dry or wet nitrous?
stock fuel pump?
did you do anything like swap MAFs?
what changes since last dynoof 370 besides the tune?
anyway to check the tune and determine if the IFR got accidentally raised and wasn't supposed to?
FWIW a mail order tune should be used to get your car to a tuner.
There isn't much info here though...
dry or wet nitrous?
stock fuel pump?
did you do anything like swap MAFs?
what changes since last dynoof 370 besides the tune?
anyway to check the tune and determine if the IFR got accidentally raised and wasn't supposed to?
FWIW a mail order tune should be used to get your car to a tuner.
Thread Starter
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From: Englewood, CO
i put two bottles through it on a 75 shot. i have the wet kit. this is the stock pump, but i watched the guage durring the run and it stayed ~60 psi. no maf swap. nothing has changed since the last dyno, not even the tune. i never shot the juice on the dyno, this was all NA. also, for 300 bucks, i would rather trailer my car to a tuner fwiw. however, i doubt it is a tuning issue NA because it did ok in the past. i do remember now that i have thrown codes for the MAP sensor. would that cause some of this.
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From: Englewood, CO
also, im going to data log the car this week with a co-workers laptop. he has efi live. hopefully that will shed some light. im just wondering if this has ever happened to anyone else.
I started to run lean too but for me I think It's because my Racetronix fuel pump is starting to break in. when my Racetronics fuel pump was new the FP would stay around 64 PSI and drop to ~ 58 PSI WOT. Now my FP stays around 58PSI and drops to ~ 54PSI WOT. I ran Sea Foam through the fuel system and re-tuned and all is fine now.
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Originally Posted by Old Geezer
" i do remember now that i have thrown codes for the MAP sensor."
Fix that problem. If the PCM doesn't know where the engine load is, there'll be no fuel control.
Fix that problem. If the PCM doesn't know where the engine load is, there'll be no fuel control.
doh! I missed that....
Yep.
Thread Starter
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From: Englewood, CO
hey guys. i checked the car on a gm computer, and with efi live. as far as it shows, all the parameters are fine. my 02 sensors say that my car is running stoich. so i think it was an exhaust leak throwing off the dyno sensors. however, the dyno numbers were still quite low. im still researching and checking. im also thinking of doing a leakdown test later on.
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From: Englewood, CO
Luckilly that dyno was screwed up or you'd need a new motor by now.If you run alot of nitrous I would recommend you invest in a wideband/gauge setup so you can moniter it. Might save you alot of $$ in the future.
