pxbacher
New Member
- Joined
- December 27, 2009
- Messages
- 1
- Reaction score
- 0
- City, State
- Kennett Square, PA
- Year, Model & Trim Level
- '94 Ranger XLT
1994 Ranger 4.0 idles fine but has been running real rough since this past summer when it started suddenly missing while driving. For a while the rough running would come and go. Now it runs rough all the time, though sometimes lots worse than other times. It starts and idles fine.
Yesterday when I first started it, it ran so badly I couldn't get it over 15mph. When I gave it gas, it backfired (which it often does when it's acting up like this and I give it more gas). After it "warmed up" it drove, but real rough. It runs worst the more I press on the pedal. It runs best when I really baby it and keep the RPMs as low as possible.
Stuff I've done so far:
1. Replaced the MAF sensor (with a used one, after cleaning it with electronic cleaner spray (not brake cleaner)) - no change
2. Replace the fuel filter - no change
3. Replaced the FPR - no change (fuel rail pressure is 29psi or better, and goes up to maybe 35 psi when driving at higher RPMs)
4. Replaced the coil pack with a used one - no change
5. Tested TPS - .95v - 4.6v nice and smooth from close to full open
Any thoughts on this? I'm thinking it's just running way too rough for it to be an ignition wire or plug problem (i.e. too many cylinders missing - can't be a single plug or wire, and there's no "central" distributor wire given that it has a coil pack). The fact that it runs fine at idle was leading me to think it was a fuel pressure problem, but after testing, the pressure seems fine. Could I have a sensor problem? What sensors would come heavily into play with higher RPMs?
Aside from sensors, I'm starting to run out of things to check/swap out, and hoping the evidence isn't pointing toward a bad ECU.
-Pete
Yesterday when I first started it, it ran so badly I couldn't get it over 15mph. When I gave it gas, it backfired (which it often does when it's acting up like this and I give it more gas). After it "warmed up" it drove, but real rough. It runs worst the more I press on the pedal. It runs best when I really baby it and keep the RPMs as low as possible.
Stuff I've done so far:
1. Replaced the MAF sensor (with a used one, after cleaning it with electronic cleaner spray (not brake cleaner)) - no change
2. Replace the fuel filter - no change
3. Replaced the FPR - no change (fuel rail pressure is 29psi or better, and goes up to maybe 35 psi when driving at higher RPMs)
4. Replaced the coil pack with a used one - no change
5. Tested TPS - .95v - 4.6v nice and smooth from close to full open
Any thoughts on this? I'm thinking it's just running way too rough for it to be an ignition wire or plug problem (i.e. too many cylinders missing - can't be a single plug or wire, and there's no "central" distributor wire given that it has a coil pack). The fact that it runs fine at idle was leading me to think it was a fuel pressure problem, but after testing, the pressure seems fine. Could I have a sensor problem? What sensors would come heavily into play with higher RPMs?
Aside from sensors, I'm starting to run out of things to check/swap out, and hoping the evidence isn't pointing toward a bad ECU.
-Pete