Help me get my '92 2.3 running right. Air/fuel problems, bad MPG.

[napjerk]

Hi everyone, new guy here with some problems, hope you can help point me in the right direction. This is gonna be a long post so grab a cold drink.

Backstory: Bought a 1992 Ranger XLT reg cab, 2.3L, 5sp manual. Got it from a guy who had it in a barn for a while and it needed a little work to get running well.

Symptoms: Engine runs OK but rich, fuel mileage around 12-15 mpg. When I got it it had some issues so here's what I've fixed or replaced so far:

New plugs (motorcraft)
New plug wires
New air filter
New fuel filter
New fuel pump (low fuel pressure, wouldn't run under load or at speed)
New fuel sending unit (gauge wasn't working)
New fuel filler neck (usual cracks/leaks when filling tank)
New thermostat
New oxygen sensor
Cleaned MAF
Oil/filter change

OK, so it runs ok but loads up a bit (rich) at idle but pulls real strong through the rev range, but like I said, it's getting bad mileage. The temperature gauge doesn't work, reads cold even though I have heat in the cab, will probably replace the 2 temp sensors as well.

Anyway, once I put the new oxygen sensor in, it started running really poorly. I think the old one wasn't working at all and it was staying in open loop. So after the new one was installed yesterday it was running ok at idle and great at full throttle but horrible at part throttle. Backfiring, loss of power, seemed like it was running way too lean. Disconnected the oxygen sensor and it runs just fine again, but smells rich (open loop). I read that to test the EGR valve you should apply vacuum to the diaphragm and it should kill the engine. I hooked up my my-t-vac pump and pulled 15 in/hg of vacuum and nothing changed, the engine kept on idling like normal. So is the EGR valve bad and introducing a huge vacuum leak? I also don't notice any vacuum at the line that goes into the EGR valve, whether at idle or higher RPM. That line comes from the EGR sensor/switch on the passenger fenderwell which has good vacuum going into it.

Now, I know the first thing you're gonna say is "is it throwing any codes?". Well remember how I said the previous owner had it in a barn? Well I found a rat's nest in the corner of the engine compartment near the EGR sensor and ECU test terminal plug. At least 4 wires into the test connector and both wires into the EGR sensor/switch are chewed through completely! So needless to say I can't pull any codes until I get a replacement harness at the junkyard. I spliced the EGR sensor wires back together but that didn't help anything. There is NO check engine light on, even while running with the oxygen sensor completely disconnected (or with key on engine off), so I wonder if the bulb even works (in the dash) or if the previous owner disconnected the CEL.

I guess my next course of action is to get a wiring harness and try to get the test terminal working again so I can pull any codes from there. I am pretty sure that the EGR valve isn't working but how can I test it (besides the vacuum trick that didn't work)? Should that EGR sensor/switch be passing vacuum to the EGR valve at idle, or just under load? Will just blocking off the EGR passage into the intake (with a blockoff plate) allow the engine to run OK in closed loop mode, or is it required for the engine to run well and not throw codes?

Hit me up with any other questions you have or ideas for me. I don't wanna just throw money at it by replacing every sensor and valve under the hood, but without being able to pull the codes that's what I feel like I'm doing.

Thanks in advance, guys.

Mike

 

[Ramirezsergio63]

timing??

 

[rrbrian222]

The EGR should be closed at idle, so as to not allow any exhaust gas to recirculate to the intake. I test mine by removing and capping the vacuum line from the top of the EGR valve, placing a spare piece of tubing on the EGR valve port and then sucking on the other end of the tubing like a straw while the engine idles. When you suck hard enough, you'll pull up on the diaphragm inside the EGR which will allow exhaust gases to flow into the intake, stumbling and then killing the engine.

Check for other vacuum leaks too. Spray some carb cleaner on vacuum lines and connections and other areas around the intake and see if the engine idle changes or stalls. Best to do this on a cold engine to lessen the fire/explosion risk. A vacuum leak might trick the PCM into thinking a lean condition exists thereby causing a fuel trim to go rich. If you end up correcting a vacuum leak, reset the computer by disconnecting the battery and let it relearn its optimum fuel trim.

I'm sure someone else will chime in with other suggestions too.

 

[napjerk]

Thanks for the replies, guys. As for timing, it's got the coil pack ignition so I don't even know how to set that, or if you even can. It doesn't ping at all and runs fine, though.

I did check all over for vacuum leaks, found and fixed a couple. There's a couple of cracked vacuum lines (those hard thin ones) that I've taped up with electrical tape until I can get replacements. No apparent leaks around the throttle body or intake, though.

Tonight I pulled the EVP off the end of the EGR valve and reached in with some needlenose pliers and tried to tug on the EGR valve diaphragm, that thing is stuck tight so I know it's not moving under any amount of vacuum. It seems to be stuck in the closed position so that wouldn't cause a big vacuum leak. I might just block off the EGR port for now. I'm gonna get the multimeter out this weekend and test the coolant temp sensor, MAF, and TPS.

 

[modelageek]

Thanks for the replies, guys. As for timing, it's got the coil pack ignition so I don't even know how to set that, or if you even can. It doesn't ping at all and runs fine, though.

I did check all over for vacuum leaks, found and fixed a couple. There's a couple of cracked vacuum lines (those hard thin ones) that I've taped up with electrical tape until I can get replacements. No apparent leaks around the throttle body or intake, though.

Tonight I pulled the EVP off the end of the EGR valve and reached in with some needlenose pliers and tried to tug on the EGR valve diaphragm, that thing is stuck tight so I know it's not moving under any amount of vacuum. It seems to be stuck in the closed position so that wouldn't cause a big vacuum leak. I might just block off the EGR port for now. I'm gonna get the multimeter out this weekend and test the coolant temp sensor, MAF, and TPS.

I think what he meant by timing was that maybe your belt jumped.

fuel pressure regulator on the fuel rail?

 

[napjerk]

I think what he meant by timing was that maybe your belt jumped.

fuel pressure regulator on the fuel rail?

Ah yeah. I'll check the valve timing, but I'm pretty sure it's OK. Literally the only difference between running crappy and running well (but rich) is unplugging the O2 sensor. Plug it in, it runs crappy and lean, pops back through the intake. Unplug it, it runs awesome, pulls hard through all the gears but smells super rich. I wouldn't think that would be the case if it was a valve timing issue, but I will make sure the marks line up.

The FPR has good vacuum into it. How do you test it? If I remove the vacuum fitting it still idles OK, but I don't think I've tried revving it with it disconnected.

 

[modelageek]

Ah yeah. I'll check the valve timing, but I'm pretty sure it's OK. Literally the only difference between running crappy and running well (but rich) is unplugging the O2 sensor. Plug it in, it runs crappy and lean, pops back through the intake. Unplug it, it runs awesome, pulls hard through all the gears but smells super rich. I wouldn't think that would be the case if it was a valve timing issue, but I will make sure the marks line up.

check the fuel pressure regulator? a bad FPR increases fuel pressure

did you get the right o2 sensor? did you get the universal one and have to wire it?

did you pull the neg bat cable for 30 minutes to reset the puter?

 

[napjerk]

check the fuel pressure regulator? a bad FPR increases fuel pressure

did you get the right o2 sensor? did you get the universal one and have to wire it?

did you pull the neg bat cable for 30 minutes to reset the puter?

No, I got the OEM Bosch sensor, had the OEM connector on it already. Ah wait, I didn't disconnect the battery after installing the new sensor, that might be a problem. I'll do that then hook up the sensor again and see how it runs.

 

[modelageek]

No, I got the OEM Bosch sensor, had the OEM connector on it already. Ah wait, I didn't disconnect the battery after installing the new sensor, that might be a problem. I'll do that then hook up the sensor again and see how it runs.

CHECK THE FPR!....I am partial to MC or Denso o2 sensors for out trucks..rockauto has the MC for about $40

 

[napjerk]

CHECK THE FPR!....I am partial to MC or Denso o2 sensors for out trucks..rockauto has the MC for about $40

OK, so when I remove vacuum from the FPR the fuel pressure should rise (at idle), right? Will check that.

 

[modelageek]

OK, so when I remove vacuum from the FPR the fuel pressure should rise (at idle), right? Will check that.

yes it should rise about 10 psi at idle and there should not be any fuel in the vacuum line.

 

[Kornfed]

I'm in your shoes... sort of...

My 89' 2.3L split coil is running like a scalded dog. Really rough idle, no low end power, burning tons of gas... been like this for a week and no matter what I check/change/replace/adjust, nothing happens. any ideas?

it doesn't have any "guts" until about 2500 rpms so it ISN'T a compression problem, or so I would assume.

 

[napjerk]

Just a quick update, the EGR valve is for sure stuck. Tested sensors today, TPS is fine, FPR is fine, the EGR control solenoid tests out OK. The Air Charge Temperature sensor was giving back crazy temperature readings; like outside air temp of 130F (it was 65 here today), the previous owner had routed the heater hose right up against the sensor in the airbox and it was pretty hot. Cleaned the sensor and rerouted the hose and it's reading closer to reality now. Disconnected the battery for a couple hours then reconnected it with the new O2 sensor in place.

Truck still runs a bit lean and stumbly at part-throttle only but not as bad as it did the other day. So I drove it around for about half an hour and about 15 minutes into driving it "kicked in" and started running great. No part throttle lag/buck, no popping back, plenty of power. Driving like a new truck. Parked it for a while and went back out, and it was lagging and stumbling a little again. Hmm. Maybe my coolant temp sensor is bad/slow to give a decent reading to the computer.

Got a new test plug harness/pigtail from the junkyard today so hopefully I can splice it in soon and pull any codes from the computer.

Still working on it...