92 Ranger 3.0 loss of power, backfiring

[slycer2002]

I have a 1992 Ranger 3.0 2wd. I recently changed out the plugs, wires, cap, rotor, and IAC, and still have to replace the O2 sensors. It has started idling really rough, and will sometimes die on me. When I manage to keep it running, the acceleration is really sluggish and I hear what sounds like backfiring coming from under the hood. Sometimes it won't backfire, but my acceleration will come and go in surges. Could this be a result of my O2 sensors still needing changed? Or is there something else going on? I replaced my ECM back in December. I got a check engine light briefly this evening, but I don't know where my code reader is. I would take it to Autozone, but the last time they told me they don't have the capability to read EEC-IV. Any thoughts? They would be most appreciated. Thank you in advance.

 

[RonD]

Firing order may be wrong, those are the symptoms, even though you know they are correct have another look and follow each spark plug wire to it's cylinder.

Firing order: 1-4-2-5-3-6
Passenger side cylinders 123, so every other wire should go left, 1 - x - 2 - x - 3
Drivers side cylinders 456 and the in betweens go right, x - 4 - x - 5 - x - 6
Distributor rotation: Clockwise (1991 - 1994)


Another issue could be a vacuum leak, this will also cause a high idle even when engine is warmed up.

Don't think a bad O2 sensor could cause a backfire, anything is possible just never heard of that.

 

[slycer2002]

Thanks for the quick reply. As you said, I'm sure the firing order is correct but I'll check it anyway. I actually did put the wires on wrong when I first changed things out but got it straightened out right away. Every once in awhile, I won't have any issues and it will sound great. But this problem is happening more and more often to where it is the norm, and periods of my truck running correctly are at a minimum. Thanks again for the suggestion.

 

[RonD]

If firing order was wrong then it wouldn't "run fine" some times, so that's not the issue.

But the backfiring should mean the spark timing is an issue, can't see a lean or rich issue(O2 sensor) causing a backfire, although a lean mix can cause a pinging/knocking noise.


Check the fuel pressure regulator's(FPR) vacuum line, see if it has a gas smell, it shouldn't, if it does then diaphragm has a leak.

If FPR is acting up fuel pressure could go low and then come back, or if fuel pump is acting up.
Fuel pressure should be 30-40psi, if it drops below this the computer and O2 sensors try to richen the mix but that can't open the injectors long enough, so run lean condition, if pressure comes back up then "runs fine" is back.

Fuel filter could even be something to look at but these usually show a first problem at highway speeds, limiting fuel flow, not at idle.


Could you have gotten some bad gas, water in it, the water will settle to the bottom of the tank when truck sits, so more water gets into the system until its driven and mixes the gas and water up again.

 

[slycer2002]

Its been acting like this for awhile, unless where I usually get gas just has bad gas to begin with. I was wondering about the PCV valve, also. It's been awhile since I changed that out, and I know that it can cause misfires at idle if it sticks open. It's a cheap item, and needs changed anyway. If that doesn't help, I'll see about renting a fuel pressure gauge and checking that out. Thanks again for the suggestions.

UPDATE: I replaced the PCV valve this evening before I went to school, and I did not have ANY problems whatsoever with the truck while driving. No stalling, no loss of power, no misfires, nothing. The truck has not run this well in years! Hell, she even chirped the tires at one point! Makes me wonder exactly how long my PCV has been bad... I'll keep an eye on things, but I'm hoping this took care of the issue. Thanks again, RonD, for your helpful suggestions.

ANOTHER UPDATE: It's been 12 days since I replaced the PCV valve, and I still have not had any loss of power or misfires while driving. I'm glad to have my truck back almost like she used to be. I still need to replace the O2 sensors, and a few other minor things, before she's the way I want her. But all said, she's 100% better than she was. Thanks again, RonD.