CHECK ENGINE LIGHT

94 Bronco, full size, 5.0 liter, EFI. Check engine light comes on after about 45 min. to 1 hr. of driving, speed is not a factor. Loses power and valves ping badly. If I turn off the engine, the light goes out for about 15 min., then comes back on. Have had a major tune-up, replaced fuel filter, EGR valve and positioning sensor, PCV valve, had catalytic converters tested. Had computer scanned several times. Indicated lean fuel mixture and O2 sensor bad. Replaced sensor 3 times. No improvement. Any suggestions?

Thanks .

Reply to
zone8
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fuel pump on way out ?

Reply to
Gary Glaenzer

Reply to
Chevy

Reply to
BattleGodz

I'd check the fuel pressure regulator next. Could be a fuel pump on it's way south too, for that matter. Sorry if I missed it but have you already pulled the codes? (Code scanners for OBD-1 speed-density units can be had for approx. $30) Is "lean condition" the only fault?

5.0 has a knock sensor that year (5.8 does not) and is probably retarding your ignition timing into oblivion, possibly saving your engine (valves) in the process. FWIW, I have only seen fuel pressure regulators fail to the ultra RICH condition but that means nothing. Have you calibrated the TPS lately? Good Luck with it and please keep us posted on your progress.

Randy

94, 95 and (son's) 96 Broncos
Reply to
rokkinhorse

What COULD be happening with the O2 sensor is that this lean burning condition is causing them to get too hot and "open" electrically. Just a thought...

Randy

Reply to
rokkinhorse

thanks randy, i was thinking about the knock sensor also, i looked it up in my manuel, but they do not say where to find it or what it looks like. any idea? jim

Reply to
zone8

No Idea Jim, sorry. Mine are 351s and don't have a KS or power steering sensor either. A wild guess on the location would be either the block or intake manifold. If you have a Haynes manual, look at the wiring diagram and find the color of the wire that goes to the sensor from the plug on the firewall, then follow it. Haynes manuals are pretty crappy but the wiring diagrams in them are excellent. Good hunting!

Randy

Reply to
rokkinhorse

thanks for your help randy, but i guess mine does not have a KS either. i looked at all the wiring diagrams from 1991-1996 and they do not list a KS. i'm having a shop here do some more testing [$$$] ,FPT, vacuum test, recheck the timing and a few other things as well. if we can get it fixed i'll let you know. thanks again, jim

Reply to
zone8

Hey Jim, I looked it up in the Haynes manual. If you have one, the wiring diagram on page 12-54 (1992 and later F-series and Bronco wiring diagram 3 of 13) shows the knock sensor location at B-10 on the diagram. The knock sensor connects to a yellow-red wire that originates from pin #23 on the PCM and a gray-red from the KS terminates at a junction (you'll see it) close to the sensor. The next page (page 4 of 13) shows both the knock sensor and the PS pressure sensor at grid location B-14 within a half inch of each other. In short, if you find pin #23 on the PCM and that yellow and red wire, you may be able to trace it to the knock sensor location. Heck, it may be HANGING from that wire and not even screwed into the block or manifold any more:-)

Regardless, best of luck to ya.

Randy Goolsby

Bronco nut

Reply to
rokkinhorse

thanks randy, i'll keep looking around until i find it. my eyes are not as go as your it seems. it now seems that the trouble is getting worse. i was able to run for about an hour now the CELight comes on in about 6 blocks. sometimes it sounds like it is starving for fuel, valves pinging like low octane, but then odor starts to come out of the exhaust. now i'm not sure if it's the KS or one of the fuel pumps. i'm going to play around with it this weekend. see ya jim

Reply to
zone8

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