1995 Ford Ranger, 2WD, 4.0L V6 Runs VERY rich at higher RPM

[paul1678pe]

Greetings Ya'll! My son and I are deep into a problem that popped up in the ford ranger described above. It's a long story, let's go by parts.

• Fuel tank broke. I bottomed out, cracked the plastic. New ones were hard to find, hard to put in….so I made my own, TIG welded out of 16GA steel, pressure tested. New fuel pump, new filter, fuel rail pressure is 30PSI with engine off and pump primed. About 31 PSI with engine at idle, about 33PSI at high idle. If I pull the vacuum line to the fuel pressure regulator there’s not fuel in it, which leads me to believe that the diaphragm has no pinholes in it, and the data indicates that the regulator is regulating.
• Catalytic converter got plugged. Blew out the incoming gasket. We redid the cat, burnt it in, redid the upstream and downstream O2 sensors while we were there.
• After this, the motor runs VERY rich anywhere but idle. It idles GREAT. Runs so rich that the exhaust is popcorning….at least that’s what I’ll call it.
• Found a few bad vacuum lines over on the emissions side. Replaced them. Found a bad idle valve controller solenoid, replaced it.
• Cleaned air intake parts with proper cleaners, cleaned throttle body thoroughly.
• Redid the coil pack, wires and plugs…..cuz they needed it.
• In view of this data, what the heck is left? If there were an injector stuck open or responding poorly, why wouldn’t that effect idle too? Glad to hear any inputs, I’ll also accept dummy slaps.
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• In view of this data, what the heck is left? If there were an injector stuck open or responding poorly, why wouldn’t that effect idle too? Glad to hear any inputs, I’ll also accept dummy slaps. I’ve ordered service manuals hoping to sit down and start figuring out what the various air, fuel, and exhaust voltages need to be and measure them. The truck has OBD2……but it’s so limited is tells nothing. Primative, first roll out. Kinda binary. “yeah, good” or “no, bad”. Haven’t see a code yet. Stupid question: since there is a ‘komputer’ in the loop…..would it be worthwhile to pull the battery post for a couple hours, let it die, then reboot by hooking it back up? Thank you kindly for the read, glad to hear any feedback.

If I take the injectors out, ground them and manipulate the fuel rail, can I just dummy test them and pish a little fuel up in the air? I'm hoping to see some of them so "psst" and perhaps one go "pooooooooooosh". then I can reckon that that one is bad........Them's technical terms....

 

[lowspeedpursuit]

I am admittedly out of my depth, but my first thought is the new upstream O2 is bad/subpar out of the box. Can you throw the old one back in and see if anything changes at all? Does the proto-OBDII show O2 sensor data?

 

[rusty ol ranger]

Are you sure its running rich?

What year is it?

Have you pulled codes?

First thing that comes to my mind is a TPS sensor.

I believe the earlier 4.0s ran an fuel pressure regulator like the 2.9....thats a possibilty if it is indeed rich, but that should affect idle too.o

If its running shitty cold and warm id bet against the O2, the engine ignores them when cold.

EDIT....

I didnt see 1995

 

[paul1678pe]

We did put in the old 02 sensors to try that notion. No difference observed. What are the basic mechanics of an injector? it's a solenoid no? Then as the engine needs more power the solenoid is pulsed longer and longer from the "komputer" to deliver more power while the throttle lets in more air. The fuel rail pressure seems pretty well regulated, and the diaphragm is in tact (not leaking)......what if the nozzle on one wore out? at low idle, you wouldn't notice. Small duty cycle. Drops vs atoms....not a big difference, but at high power, it's {exagerated] a shot glass vs a spit. gotta try to dig into diagnostics more. Maybe there's a way to see what we are guessing at. Then get the manual, start poking voltages. Guessing sucks. But we needed the new parts, so what the hell?

 

[rusty ol ranger]

We did put in the old 02 sensors to try that notion. No difference observed. What are the basic mechanics of an injector? it's a solenoid no? Then as the engine needs more power the solenoid is pulsed longer and longer from the "komputer" to deliver more power while the throttle lets in more air. The fuel rail pressure seems pretty well regulated, and the diaphragm is in tact (not leaking)......what if the nozzle on one wore out? at low idle, you wouldn't notice. Small duty cycle. Drops vs atoms....not a big difference, but at high power, it's {exagerated] a shot glass vs a spit. gotta try to dig into diagnostics more. Maybe there's a way to see what we are guessing at. Then get the manual, start poking voltages. Guessing sucks. But we needed the new parts, so what the hell?

Doubtful its injectors....to cause it to flood that bad you would have to have all 6 fucked up at once....very unlikely.

Get a code reader first. Pull the codes.