Here is my situation. rchased an s-13 sr. I struggled with the getting the motor to idle and accelerate smoothly, only to find out after two weeks of troubleshooting that the MAFS that I had been told was tested good was faulty. I replaced it with a Q20 MAFs (I am not sure if it is truly compatible, but the motor ran great). After about 20hrs of driving time, I noticed a rare exhaust backfire, (I figured that I would have time to get it home and adjust the timing). After shifting hard into 2nd gear the car sputtered black smoke and bogged down. I have spent sevearl weeks now troubleshooting everythign I can think of. I attribute part of my problem to the Blitz DD BOV as it vents metered air into the atmosphere vice recirculating it. As far as I can tell the ECU is good, MAFS good, O2 good, EGT good, no vacuum leaks, good compression, solid intake piping, good pressure regulator, fuel injectors (very misty pattern) good ignition circuit. I am about out of ideas, I ahve tried resetting the ECU, with no avail, the ECU doesn't call out any fault codes (although there are no LEDS on it as it is a factory refurbish unit).
If I let the car sit for a few days it will start and run for a few seconds then die due to the cylinders being washed down.
Any help is greatly appreciated.
Very rich A/F ratio....HELP!!!
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quiksilvia
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Movingviolation240
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- Car: '95 Nissan 240SX 400hp SR20DET -SOLD
'93 Lexus SC300 w/ SP66 turbo kit
Unplug the maf and it should idle for you when you start you just cant drive or rev up without it. I believe the q20 is the wrong one and doesnt have the proper voltage requirements to communicate with the ecu and other sensors. and if you had an apex afc or retuned ecu it would work but more than likely its your maf. Your bov is proly fine and if you want route it back into the intake just for testing purposes or to leave it like that. Either way there are ways of gettin it to run right with it open atmosphere. Do you still have the other maf? If so have you tried to clean it?
quiksilvia wrote:fuel pump/filter, see if u can run w/o the bov, get a stock one
The fuel pump/filter is good, if it were bad I would get no fuel, or not enough fuel to create a rich condition. Thanks though. I have tried to run without the BOV, no go, still over rich. It was only my idea that the BOV caused the ECU to learn a rich mixture. I had the battery disonnected for a good deal of time, hoping that whatever was stored in the memory would reset and the ECU would go back to the firmware settings, this didn't work and leads me to believe that the problem lies in a sensor/s.
Movingviolation240 wrote:I don't think the G20 MAF is the 'right' one. Try a KA24E unit and see if that helps you any.
Also have you looked at the o2 sensor, if you unplug it you might be able to see if it works better, worse, or indeferent and see if that could be a cause.
Paul
Thank you for your input. I am leaning towards the Q20 MAFS as well, but I still can't explain why the car ran great for a period of time with it. In fact the first MAFS that I had was the S13, that MAFS caused the engine to idle very poorly and had no throttle response. I will try disconnecting the o2 sensor and see if that causes any difference, but my understanding that the o2 sensor only has an effect during closed loop operation, ie.. once the engine has warmed up.
MojoMan wrote:Unplug the maf and it should idle for you when you start you just cant drive or rev up without it. I believe the q20 is the wrong one and doesnt have the proper voltage requirements to communicate with the ecu and other sensors. and if you had an apex afc or retuned ecu it would work but more than likely its your maf. Your bov is proly fine and if you want route it back into the intake just for testing purposes or to leave it like that. Either way there are ways of gettin it to run right with it open atmosphere. Do you still have the other maf? If so have you tried to clean it?
What would you recommend doing to keep the BOV open atmosphere? Do you know of any adapapters for the Blitz DD BOV to recirculate the vented gasses? Thank you.
Do you have the horn attachment or the filter on the bov? If you have the filter attachment you might be able to take it off and slide a recirc. hose on it. Someone should now if you can. I use the HKS so Im not sure. I also didnt know that it had driven with the q20 maf. I missed the20 hrs thing. I though you had just put it on. I think you would be better off with the ka maf. Also what ecu are you runnin? Is it retuned? If so it could be tuned for the ka. You never know. Let us know what ecu your using. Have you checked all of you I.C. piping as well? Checked all of your connection points and pull on everything to see if any are sliding off.
I have since checked the voltage and resistance vaues of the q20 MAFS. I do not think that this is the problem anymore. The resistance levels at rest are exactly the same as the sr20 MAFS. If the dc voltage levels are correct, current would be correct and identical (ohms law, and Kirchoffs law). Because my fuel pump works, the fuel filter is unobstructed, all lines are good, and I still have an over rich condition, the only thing that is left in the line is the fuel pressure regulator. As this is located ion the return side of the fuel rail, a constant closed, or mostly closed fuel pressure reg. would cause massive amounts of fuel to be pushed through the fuel injectors at even the smallest pulse width, thus causing a condition so rich that the car would not be able to start. This is all theory, as I haven't had the chance to test the FPR. If you have any contradictions, please feel free to respond.