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Ok so here's my deal, I bought my 90 gt last summer and it was carbed. Last winter I swapped it back to efi. I was running it since Father's Day until last weekend with a pinched return line and about 80 psi of fuel pressure. I fixed the return line last weekend and now have the stock 38 psi of fuel pressure. I have drove it a week thinking the eec would relearn the injector pulse width but it still falls on it's face and pops and misses over 70% throttle. It also runs poorly until reaching normal operating temp. I have tried leaving battery unhooked and that didn't work. If I pinch the return line to raise the pressure it runs good. Can someone please tell me if there is a way to reset the eec fuel tables or a way to make it relearn quicker or how long will it take to relearn? Any help is greatly appreciated it's very annoying driving like this. Thanks
 

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Sorry I left out my setup was in a hurry. It's a .060 over 302 with Motorsport y-303 heads, explorer intake, tfs stage 1 cam, crane 93 cobra 1.7 rockers, 24 lb injectors, pro-m 77 mm mass air calibrated for 24 lb injectors, 75 mm throttle body, cold air intake, stock fuel pump and regulator. I did not realize I had a pinched return line until I put a gauge on it and seen the 80 psi. So I fixed it and it runs bad if I pinch the return line it runs good. I have read that the eec don't use O2 sensor feed back for above 70% throttle and that is when it runs rough popping through intake, missing, no power etc. it also runs terrible until it reaches normal operating temp. Even if I shut it off for a quick 5 minute stop at the store and the gauge is still reading 180-200 degrees it runs like crap for a few miles. I have left the battery unhooked for an hour and it didn't help. I don't know if it's something else but It seems like since I drove it 3 months with the 80 psi it has learned to pulse the injectors a very short time. Like i said if I pinch the return line it runs good and that's why I believe my problem is with the eec fuel tables. But I'm open to try anything at this point
 

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I was running it since Father's Day until last weekend with a pinched return line and about 80 psi of fuel pressure. I fixed the return line last weekend and now have the stock 38 psi of fuel pressure. If I pinch the return line to raise the pressure it runs good.
Car was tuned with 80psi of fuel pressure that is obvious. Raising the fuel pressure by pinching the line is proving that. Now with 38psi of fuel pressure you need a retune.
 

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Car was tuned with 80psi of fuel pressure that is obvious. Raising the fuel pressure by pinching the line is proving that. Now with 38psi of fuel pressure you need a retune.
It's only an EEC & he disconnected the battery for an hour.
 

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Yes plugs wires cap rotor and fuel filter are all new. Tried cleaning O2 sensors made no difference then tried my friends new ones and made no difference.
I never had it tuned with the 80 psi. It's just my theory that the eec compensated for the 80 psi by shortening the injector on time and it ran good the whole time I was driving it like that. So my theory is that now it's still pulsing the injectors as if it had 80 psi so now with the 38 psi it's not getting enough fuel. But I would have thought disconnecting the battery would have reset it or the couple weeks I've been driving it would have relearned by now. Does this theory of mine sound legit or is something else going on? I feel that since if I pinch the return line it runs good again kind of backs my ideas.
 

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Have you visually inspected the ECU to ensure a tuning chip isn't present? A stock ECU does not see fuel pressure. The feedback related to injector pulse will be the O2, ECT, IAT and MAF signals. Pull the Trouble Codes (DTC's) to see what the ECU has logged.
 

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Have you visually inspected the ECU to ensure a tuning chip isn't present? A stock ECU does not see fuel pressure. The feedback related to injector pulse will be the O2, ECT, IAT and MAF signals. Pull the Trouble Codes (DTC's) to see what the ECU has logged.
Doesn't see fuel pressure, but it does see AFR via the O2. There's something else going on with the fuel pump, FPR, etc. Been there, done that.

OP history of events is somewhat like mine:
1. "pinched" return line.
2. high fuel pressure.
3. blocked fuel pump inlet
4. no anti-siphon valve in FPR.

It's sure beginning to seem like it's the fuel pump and/or FPR.
 

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I guess you have a fuel pressure guage on the car that you can see the pressure while driving? I have an adjustable fpr I can send you if you dont have one you can try. That way you can crank the pressure back to 80 to verify the problem goes away. Im leaning mor toward mass air meter. Do you have another mass air to try?
 
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