stkelver
New Member
- Joined
- July 8, 2009
- Messages
- 3
- Reaction score
- 0
- City, State
- Conroe, TX
- Year, Model & Trim Level
- 2005 Explorer
We have a 1998 Ranger 4x4 ext cab with a 4.0 V6 engine. We bought it used a few weeks ago. It had a misfire issue when we purchased it. Brought it home replaced plugs and wires. The misfire is gone. The number 1 plug was soaked with gas when we replaced it. Codes P0172 and P0175 are what we are currently trying to service. After reading many threads here we tried cleaning the MAF sensor. This was unsuccessful, so we replaced the MAF sensor. Again an unsuccesful repair. We went through and checked the IAT, TPS, IAC, ECT using a volt meter to perform various voltage and resistance tests as described in the Haynes OBDII book. We took apart the upper and lower intake manifolds and found a few possible problems (two upper intake gaskets). We replaced a leaky fuel injector (@ the #1 plug) and put the correct gaskets, new o-rings on all injectors, new fuel rail bolts that were damaged. Ran it for 40+ miles with no CEL and then it came back on. Ran to Auto Zone and it is still same codes. Changed PCV valve. Checked for vacuum leaks with propane and starting fluid. Checked fuel pressure at the schrader valve it was 52psi KOEO and 64psi KOER. Most of the threads that I have seen discussing fuel pressure on this site the KOEO and KOER pressure is within a couple of pounds of each other do we have a concern with our pump here? Haynes says 55 to 72 psi is good. Also, we have replaced the fuel filter. In doing the voltage and resistance tests on the various sensors there was one that has us questioning. When we checked the MAF sensor the Hanyes procedure said that there was a supply voltage of 12V and a +5V reference from the PCM. We do not have the reference +5V from the PCM.
The symptoms that we are experiencing are high idle (1100 rpm), horrible gas milage (12MPG), occassion smell of gas, black exhaust. There is a slight roughness in idle but unlike any described in the threads we have looked at. Ours sounds like it is running well, but again there is a very slight roughness sound.
We read a thread today where a guy was stating that most sensors could be disconnected while the engine was running and the computer would have it run in a "safe mode". We tried disconnecting the MAF sensor and that very light roughness seemed to go away.
Does anyone know if the reference voltage from the PCM not being at the MAF could cause this?
We are trying to find this problem but are running out of ideas. I also saw an old post talking about heat, we are in TX and it has been very hot, would that effect anything we are searching for?
The symptoms that we are experiencing are high idle (1100 rpm), horrible gas milage (12MPG), occassion smell of gas, black exhaust. There is a slight roughness in idle but unlike any described in the threads we have looked at. Ours sounds like it is running well, but again there is a very slight roughness sound.
We read a thread today where a guy was stating that most sensors could be disconnected while the engine was running and the computer would have it run in a "safe mode". We tried disconnecting the MAF sensor and that very light roughness seemed to go away.
Does anyone know if the reference voltage from the PCM not being at the MAF could cause this?
We are trying to find this problem but are running out of ideas. I also saw an old post talking about heat, we are in TX and it has been very hot, would that effect anything we are searching for?
