I have a 97 Ford Ranger XLT, 4wheel drive, 4.0 liter with 145,272 miles on it. For several months it has been running rough off and on but recently it has gotten much worse. So far, this is what I've done to attempt to fix the problem.

125,173 miles: It was running rough but wasn't throwing any codes. I had the following done: Injectors professionally cleaned, Replaced Fuel filter, PCV valve, Spark plugs and wires. It ran better for awhile but started running rough again within a few months.

Months later it threw a code indicating the MAF sensor needed replaced and I did so at 141,403 miles. It was still running rough off and on. The problem was sporatic at best.

144,772 miles: replaced plugs with platnum Plus 4s (went from Platnum plus to see if it would help - it did but only for a little while.

Several weeks later, it began throwing mulitple codes ranging from P0133, P1131, P0171, P0304, etc (within the last 3 days)

145,214 miles: Replaced O2 sensors. It stopped throwing the other codes but ran even rougher and continued to throw mulitple P0300+ codes (cylinder misfire).

Today:
145,264 miles I replaced the plugs (again, going back to the platnum plus) and wires, ignition coil, PCV valve, crankshaft position sensor and checked for vacuum leaks. That helped a little but is still missing. I have driven it less than 10 miles since doing the last repairs and it hasn't thrown another code (yet). It's still not running right though. Any suggestions would be appreciated.

 

Well OK maybe time to do a compression check on the cylinders. How do the plugs look when you change them? Does it run rough at idle or all the time.

 

Have you disconnected the battery to erase the trouble codes & wipe the computers fuel trim tables, so it can begin to rebuild new tables after the O2 sensor replacements & other repairs????

Did you use the specified OEM Motorcraft O2 sensors, plugs & wires, or store brand aftermarket ones????

Have you ever replaced the air filter & cleaned the MAF sensor????

Have you done a "cylinder balance" test, or a compression test????

 

Thanks for the responses 150ford and pawpaw.

Sounds like my thoughts have been on same track as yours have. I'll have to get a mechanic shop to do additional testing as I don't have the equipment to check compression, fuel pressure, cylinder balance, etc myself. I was looking to see if there was anything I was missing.

Just to answer a few questions: As you read above, it had been less than 1,000 miles between replacing the spark plugs so they didn't look bad, only slightly grey. I kept the ones I took out this time.

It is running rough all the time now. A few days ago, it was just missing randomly, sometimes idling smooth, then I'd go down the road and it would start bucking, other times it would start out idling rough and smooth out a couple miles down the road.
It's been maddening to try and figure out what was going on. It was actually a relief when it started throwing trouble codes.

I have a code reader so I can erase codes when I've read them but I did take the negative battery cable off, once to allow the computer to reset a few days earlier and today when I replaced the crankshaft position sensor.

If you can think of anything besides what you've mentioned above, let me know. I plan on making an appointment with a mechanic early this coming week and I'd like to be able to give them a list of everything I did to try and fix the problem before going to them and I would also like to know I did everything I could before I go in.

 

If you have a scantool, it may be able to perform a "cylinder balance" test.

You could have a underhood look after dark, to see if you can detect any high voltage breakdown, maybe even perform a individual ignition wire & coil pack "wet down" test, with a spray bottle of water & see if you get any fire works, or rough idle.

Were the replacement plugs & wires OEM????

We need heavy duty wires & double platinum plugs for our "waste spark" ignition system, as it works those components twice as hard as the old distributor & single coil ignition.

We need double platinum plugs as one bank of cyls gets a reverse polarity spark, so regular plugs or single platinum won't last long in that bank.

More thoughts for pondering.

 

pawpaw,
Thanks for the suggestion to check running engine under the hood after dark. Turns out that one of the new spark plugs had a hairline crack. Replaced the plug and now it purrs!

 

ALLRIGHT, way to go, good troubleshooting find, fix & feedback & to hear it seems to be ok now!!!!