My Ranger is sick

[Okrazie1]

I have a '95 2wd shortbed, 2.3L, manual tranny with 48k miles which I bought in June of last year. In the last 6 months or so it would, on occasion, stumble when accelerating. It feels as if it is losing power completely. At first this would only occur once then go away and might not happen again for weeks. It has progressively gotten worse to where it occurs at least once every time I drive it. Sometimes it will stumble three or four times in quick succession, then immediately clear up. Today I borrowed a scanner to check for codes. No DTC’s were present. I spent some time driving around with the scanner hooked up and recorded data when the problem occurred. One of the few things I saw that didn’t look right was TPREL voltage would increase from 1.06v to 1.25-1.30v when it stumbled, and the fuel control system would go from closed loop to open loop. In the following 30 seconds or so TPREL voltage would then decrease back down to 1.06v and the system would switch back to closed loop. RPMDES also changes during this time from a steady 725 up to roughly 1100, then returns back to 725 during the same time period. My understanding of TPREL is it is the voltage drop across the throttle position sensor when the throttle is closed, and it is relearned every time the engine is started. I’m not sure what RPMDES represents. I thought that I might have a bad TPS, so I changed it. The problem is still there. I’m at a bit of a loss as to what to check next. Any ideas?

 

[RON COX]

Have you checked the fuel filter or fuel pump. Take a look at your PCV also.

 

[Ricardo Miramontes]

My Dad has '94 Ranger with the 2.3L engine (8 spark plugs) and had been having similar prolems as you have described. If I understand correctly you are losing power when accelerating? My Dad also experienced sluggish climbing. He checked all sorts of things from fuel pumps, fuel filters, fuel pressure regulators, timing, and it turned out to be the mass airflow sensor. He cleaded that up and it works fine now. You may want to check that out anyway, it never hurts to clean it.

I hope that helps

 

[Okrazie1]

I think I figured out what is happening, now I just have to figure out why. I believe that the PCM is losing its power source. This is causing the ignition to drop out, since the PCM directly controls the firing of the coils. This would also explain why the TPREL voltage jumps up. Since I'm at part throttle, when the power is interrupted and then reapplied, the PCM sees the part throttle voltage as the lowest since it was powered up and uses that value as its reference. I noticed this morning that if I continued to drive at a steady pace after the engine cut out, the TPREL voltage would stay at the higher value until I let off the gas, then it would drop back down to its usual value. Now all I have to do is find what is causing the PCM to lose power .

 

[Okrazie1]

I'm dragging up this thread to say I finally found out what was causing this. It had cleared up after shaking around the underhood wiring shortly after the last time I posted here, then late last summer it started again. Last week the truck completely died on me, then after I pushed it out of traffic, it started right up. When I got home I took a screwdriver and used the handle to shake around the wiring. When I was shaking wiring near the battery, the engine stumbled. I did it again, and I saw a spark at the power steering pump. Come to find out the wiring going to the evaporative cannister purge valve had rubbed against the power steering pump and had wore through the insulation, and when it would make contact with the power steering pump, it would cause the truck to cut out. I taped the wiring up (and managed to break the outlet off of the valve in the process, since the plastic had become brittle, so I had to replace the valve), and the problem is gone.