Fuel upgrades, car won't run. Need help ASAP! :(

Rick 91GT · Apr 19, 2004

Dave, what a PIA.......

Still haven't figured out why the TPS kept the car from priming, I am only assuming now it was due to the bad EEC. So now it has Fuel and Spark, but won't do anything after idling for a few moments.

Mikes right about the luck, maybe you guys are long lost brothers..lol

Mike I have a lead on a nice 4 eye'd front end, supposedly it is in almost perfect shape, once the car is stripped of what my buddy needs the entire body and balance of the car goes for $500? E-mail me.... Rick91GT@suscom.net

Mike86Stang · Apr 19, 2004

Rick I'll shoot you an e-mail..is this a 4 cyl car or aGT??? TIA

PIP= Profile ignition pick up. It's inside the distributor & is the electronic piece that the TFI hooks to, ussually leads to an erradic idle... if something screwed up there it may lend itself to the issue. See if you can swap distributors with someone...Good Luck!

jrichker · Apr 19, 2004

Check the red wire on the IAB for +12 volts. No +12 volts and you have a bad wire/bad connection. This is the same +12 volt circuit that feeds the injectors.

Mike86Stang · Apr 19, 2004

I noticed that when I ripped my harness apart & soldered some connection
& was checking the wires... some of ford wiring practices I think is questionable.

Ozz · Apr 20, 2004

Update:

My friend was at my house this morning, I was here at work, and this is what he told me:

He pulled a couple codes and got one regarding the o2 sensors, and one regarding the throttle sensor being too low. He checked it at 1.14 (should be .97 but it must've been moved around in all our work). But how is that too LOW?

As well, his service shop book says the o2 sensors should have a resistance of 6K ohms (I think that's what he said), and he was not able to pull any resistance reading on my digital multimeter. He got a pair of new sensors, and got the same reading. Should these be plugged in while taking the reading or not? He said he did the test without plugging them in. So that might be the problem there, though he was hesitant to install them if I didn't need them and won't be able to return them. Heck, it's time for new sensors no matter what, so I don't care. Just want to Stang expert opinions.

So that's where I am now.

Also, the ground wire for the injector harness, the little orange wire going to the back of the head, had become corroded and broken at the end. We gave it a new ground under the braided strap that goes from the block to the firewall. We were getting stupid with our experiments with the car, since we had been out of ideas on what to do, and we found that whether that wire is grounded OR NOT, the car acts the same, whereas it will start up and die out. However, if we keep opening the throttle plate, the car will continue running.
When it gets warmed up, it acts better and idles longer but we still need to move the throttle plate around to keep it going for long periods of time, say longer than 60 seconds.

Mike86Stang · Apr 20, 2004

One wire is ground on the O2's one is the signal wire... it should switch between above.5v & below.5v (I think some one needs to verify the voltage switch). You really can't determine anything without the car running as far as the O'2s go. I'm thinking you have a wiring issue with the TPS at this point... check the readings at the sensor & again @ the EEC if they differ there is your issue.

jrichker · Apr 20, 2004

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.
The O2 sensor ground is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than .4 volt. Remember lean = less voltage.

" When the mixture is rich, there's less oxygen in the exhaust than in the ambient air, so voltage is generated between the two sides of the tip. The voltage is greater than .6 volt. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage."
Charles O. Probst, Ford fuel Injection & Electronic Engine control

Ozz · Apr 20, 2004

Thanks, I will check those when I get home.

From the info I gave today, do the 02s seem like a possible candidate for the problem? Or just a little part of it?

jrichker · Apr 20, 2004

mansonozz said:
Thanks, I will check those when I get home.

From the info I gave today, do the 02s seem like a possible candidate for the problem? Or just a little part of it?

You could disconnect the O2's. The car would run pig rich and and probably go into limp mode, but it would still run. You might have to set the idle way high, 900-1100 RPM, but it could idle without playing with the throttle.

Mike86Stang · Apr 20, 2004

Personally I doubt the o2 theory but anything is worth testing at this point.
I'm still thinking TPS wiring issue.... is your v-ref 5 v on all applicable sensors?
If it's not there's a good indicator there.

Fuel upgrades, car won't run. Need help ASAP! :(

Rick 91GT

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I think I have a problem here.

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