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.

 

[paul1678pe]

First, thanks for the great advice and support. And now, A bit of an update:

We got to digging in. OBDII scanned doesn’t tell us a whole lot, but the live data was handy once we figured out how to access it.

Throttle position: working. Value moves, tracks in proportion to throttle impetus.

Mass flow sensor: working. Value flutters around a bit, as we’d expect.

Fuel injectors: Wow. We pulled the fuel rail, inserted the injectors, dummied up a fixture to hold them and made sure ground was proper……5 injectors go “pst” and one goes “POOOOOOOOOOOOSSSSSSHHHHHHH” and stays open. Goodness. Why? Take the darned thing apart and find a hole in the diaphragm. Whenever fuel pump is on, injector can’t hold it back.

OK, replace all injectors. They are all old, failure coming for all of them, why not start over. Great, clean throttle body, intake, new gaskets. Dropped a socket down the intake, had to buy a bore camera and get funky with a coat hanger and a magnet, but we got it. Par for the course I guess.

Ignition. Wow, plugs are ancient. Don’t like em. Replace plugs. Holes look great, cylinder walls nice and pretty, cuz we got a borescope now, so why not? Wires suck. Replace wires. Sixpack coil pack….eh…it’s old too, why not.

Data still really wonky on live analysis. O2 sensors WAY out of whack. Two don’t move at all. 0.01V on computer, similar value with piercing probes and a Fluke DMM. Whuh? So I was thinkin. What does O2 sensor heater draw? Found about 2A cold, about 1/2A hot. So if the fuse on the output of the O2 sensor heater relay is 15A and I pull that fuse and replace it with an ammeter, I should see about 6A cold, about 1.5A hot, give or take. Nope. 2A cold, 1/2A hot. Whuh? Current don’t lie man. Why isn’t the current getting to the sensors?

Pull the harness from the ECU, find pin counts and pin numbers in manual. One to one correspondence at the vehicle side of the connector, half of the connections don’t pass to the O2 sensor. Damn, two connectors bad. Shucks. OK, replace all O2 connectors, screw the new sensors back in. Now we got data, AND current flow to the heaters. Yay. Data shows that we are running richer than hell. And we are. Work under for 20 minutes and you are stoned with a headache. Get big barn fan.

And then we discovered the ‘mistake’. Firing sequence is 142536. Coil pack connects as 123546. UGH! Why not one to one correspondence??? Took a while to figure that out, ran richer than hell during that time, made hardly enough power to shift. so we switched the appropriate wires.

In the process we killed the new catalytic converter. VERY restricted, couldn’t cook it back into operation. So we accidentally jammed a ¾” hunk of black pipe through the tube, smashed all the ceramic stuff and dumped it out wearing proper PPE of course. New cat is on order of course of course, wouldn’t want that gross error on the street, heavens no. Then we had to adjust flow exposure of the downstream O2 sensor a bit to get it to idle, but as soon as that new cat show’s up, we’ll bolt her in post haste and be compliant with policy or whatever it is. Post haste of course.

And now the live data looks good to me, truck runs great, makes good power. A smidge less attenuation on the exhaust stream, but not too bad. It’s not a fart pipe or a gangsta compact….it ain’t a roaring 426 hemi either.

Now we are down to an ABS light and a need for a new radio. I suspect the sensor on one of the front wheels is dirty. New radio, eh, it’s a single DIN, lots of nice stuff available. Got a little room in back for a sub.

Also replaced a ton of vacuum hoses that didn’t look so hot and a few ground straps. top and bottom rad hose, belt, tensioner.

Learned a lot on this one gents. Tough to commit time to the fuel, spark, ignition, exhaust loop on a part time basis. I don’t think there are too many modern “google techs” that could have got through this one. I’m kinda proud we did.

Thank you kindly.