to rich to drive.

EVO9_Inside · Oct 5, 2013

So, 1991 gsx, stock compression forged motor, crower oversized valves, springs, retainers, stock cams, 20g turbo.
No egr, with blockoff, pcv deleted. Correctly ran vacuum lines to the WG, bov fpr. Safc tuned.

So when i start the car, it starts up fine, idles fine at 1700 warming up, but my afr is richer than it can read, tons of fuel coming out the exhaust, ect. If i press the throttle it misfires and stutters, making it undriveable, if you slowly apply throttle is revs almost normally.
Ive gone through the intake system twice. I cant find any leaks, passes the leak test, i have a feeling my unfamiliarity with obd1 is confusing me and keeping me from an easy diagnosis.

Anybody have an ideas?

92AWDHX40 · Oct 5, 2013

Check the 02 sensor, grab a wideband for accurate readings did you do a boost leak test, you said no leaks but did you do a boost leak test?

chris00326 · Oct 5, 2013

Sounds like a bad maf

EVO9_Inside · Oct 6, 2013

I also have a 2g maf on the car, i forgot to mention.
And it passed a boost leak test, and the wideband says 10.0, unreadable richness.

92AWDHX40 · Oct 6, 2013

Could be another issue besides your richness.

EVO9_Inside · Oct 6, 2013

Well, no it cant? The only thing that can cause a wideband to be rich, is richness? Its not shorted in the wiring, it reacts correctly to the throttle applied.

evoredy · Oct 6, 2013

Check the wiring from the SAFC to the ECU. Maybe something came loose on the MAF intercept wire. Also, Make sure the SAFC settings are still set. Remove the SAFC from the loop and see if it "went bad." Don't forget to jump the MAF intercept wire or use the included jumper plug that originally came with the SAFC.

Mine lasted forever and it still works, but I have heard some stories. What fuel system components do you have?

EVO9_Inside · Oct 6, 2013

Fuel is some blue top injectors ,walbro 255.stock everything else.
Today i re tested the boost test and my damn throttle is leaking. Had to use soap water to find the leak, so im going to rebuild it this week and see what happens. Im betting it will aleviate a large part of the issue.

OutKastGSX · Oct 6, 2013

Also if you are using the stock fpr. You may be overruning it. I have a similar issue with my wally 255 being to much i believe. I am getting the kit from extreme psi just for good measure. Maybe something else to check out if this dosent solve your problem. Good luck.

ninjadave · Oct 6, 2013

Yeah outlastgsx is correct, if your running a 255 pump on the stock fpr your definitely over running it and need to get an afpr (adjustable fuel pressure regulator) and that should solve the richness along with the boost leak you found.

evoredy · Oct 6, 2013

I've run a 255 HP (un-modded) on my bone stock 95 GSX and I was able to keep the fuel in check. I also had an SAFC and 625CC injectors and it still idled stoich. I guess mileage varies with every person and the age of the FPR. He shouldn't be pig rich that way though. The only way to know is to put a pressure gauge on the rail area or return line.

Good luck OP.

EDIT: Pull the rail up with the injectors attached and use a program like EVOSCAN to activate the fuel pump and see if your injectors are leaking. Also, I noticed your handle says "EVO9_Inside." If you are running an EVO8/9 ECU with a 2G MAF, make sure you have your MAF tables rescaled for that MAF.

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