mstahoo

Hi guys, I have a APR and in line fuel guage. The concensus around here is 40-43lb at idle. I had a lean condition a while back, causing pinging(at high RPM) and check engine lights, etc. We realized I needed to increase fuel pressure. Did that, and the pinging went away, check engine light turned off. The problem is, Ive done this 3 times, and after about a month, it all starts happening again. How could this be, when I am manually adjusting fuel pressure? Could the PCM be compensating? The other thing is that I have a PRO-M computer in there, it is not programmable, and is designed to run my sn95 set up as a 93 generation. Im at a loss. If anybody has any ideas, I would appreciate it greatly. If you need to know other mods just ask but, I dont think thats relevant to this matter.
Thanks
~Marco

mattdel

Pressure is WAY too high unless you're running a 700hp methanol motor.
31-33psi idle, 37-39psi WOT.

Mike T

Pull the spark plugs and see which cylinders are running lean. You may have some stopped up/weak injectors. The plugs will tell you a lot.

dawson1112

there is probly an underlying problem leaning the engine out. Could be as simple as a o2 sensor or ect sensor sending false readings. You increase fuel pressure and it solves it for a bit. once the ecm recalculates all the data it leans it back out because that is what it thinks it should be. I bet if you clear the computer out by disconnecting the battery , the next start will be way rich.

mjr46

It happens cause you are treating a symptom and not the root cause. I don't ever understand why people adjust the fuel pressure over stock specs as mattdel states..........It will not ever fix an inadequate fuel system/and or lean condition when the ecm has adaptive learning.....this means when you adjust the fuel pressure over stock, the ecm will soon see a rich condition and trim back the inj pulse, while what you did may correct it for a few days/ weeks, eventually the ecm will adapt back to where the tables are programmed to be and trim the pulse.....that is why the prob returns...you have not fixed the root cause.

mstahoo

@Matdel, nah I searched for along time, 40-43lb at idle is the way to go with #24 injectors and my mods. Had the car dynoed and the performance shop who did it concurred. @Mike T, pulled the plugs and they all look perfect(light almond color) @Dawson1112, I have an o2 sensor-less set up. @Mjr46 an FPR is how you adjust air fuel mixture on my set up. Remember, even though its a 1997, the car has an sn95 5.0 motor in there, being run of a 1993(foxbody) management system. All tuning such as timing and fuel pressure/air fuel mixture has to be done manually. Could the MAF be acting up? Thats the only other thing someone else suggested?......
Thanks for the responses though...keep em coming...

mattdel

You can't run without o2's on an electronically controlled engine. That's problem #1.

dawson1112

You may have had the data points set manually but the ecm still needs to have control over the air/fuel mix and timing. It does this via 02 sensors, engine temp readings , mass air readings , and other inputs. You cant just set it at a certain point and lock it down like a carb. And yes it could very well be a maf problem, but like I said increasing fuel pressure is only temporary until the ecm collects enough data points for the adaptive learning to start regulating things. The fpr has no control over your air/fuel mix, its all done with engine management in the ecm. With out 02 sensors the ecm is very restricted in what data it collects , and even using the dummy 02 plugs with the resistors is gonna give false readings.

mstahoo

Ok thanks guys. I was wondering if the dummy 02 plugs were problematic. Im gonna clean the MAF, and look into ecu tuning but, I heard the PRO-M I have in there is untuneable. When I baught the car the previous owner had the spout connector out, and the timing at like 30 degrees.......hmmmmmm..

Stay tuned...literally, and physically. lol!

mjr46

All my recommendations are based on using stock equipment/set ups. If you are running some hack set up, no one will be able to effectively make good recommendations......if you are running a eec iv from a fox, everything/sensor must be hooked up. Otherwise, the ecm will enter a FEM mode (failure effects management mode) where it will substitute a known good value for a failed sensor. You have handicapped the ecm ability to manage the efi system. Wire and restore everything to stock and you'll find it'll work better. My guess is, there is a lot not wired/set up/ hooked up right in accordance with how the factory intended it to be since a conversion was done. good luck, Oh and FYI what I said previous is correct when dealing with oem