gdonham
New Member
- Joined
- May 6, 2008
- Messages
- 5
- Reaction score
- 0
- City, State
- Houston, Texas
- Year, Model & Trim Level
- 1999 Explorer SPort
Can someone please help me with diagnoising this problem. First of all this has been a problem that has crept up. The problem started only when the temperature was below 60 F. The codes would clear if battery disconnect was performed. As time went by the problem became continious. The current condition is "check engine" light on and codes P0171 and P0174. The diagnoistics done so far are:
Engine is 4.0 E OHV in Explorer Sport 1999.
1. MAF sensor cleaned. I have monitored this sensor with a scan tool and the output seems normal.
2. The vacumn system has been checked, visual and some parts like egr diagram checked with vacumn pump, all seems good.
3. The only hard symptom is when the computer is reset and a drive cycle is performed the EVAP Monitor test fails and the P0171 and P0174 are diaplayed. I dont know if the test fails because the codes appear or it is the source of the codes.
4. The air filter and fuel filter are fairly new. The fuel pressure is going to be checked but my gague has a larger connector than the value on the fuel rail. Will test fuel pressure soon.
5. If you look at the internet for symptoms the #1 is MAF, but that seems normal. The second is vacumn leaks, I have checked all but the EVAP canister. When I pulled a vacumn on the EVAP cannister I could not get a vacumn to hold. THat may be normal if the vent is not closed. I will investigate that and see if the cannister will hold a vacumn.
6. The only other visable is a small rubber host is hanging down at the differntial. I will investigate if that is the tank vent or something else.
7. The long term fuel trim tables are maxed. Since the engine thinks it is lean the fuel table is maxed. The plugs look good as far as color. The plugs are in the normal color (slight yellow), no spots or burning, not extremely white, no oil fouling.
8. Either I have a fuel pressure problem, i.e. too little fuel, or a vacumn leak. Since the EVAP Monitor diag failed I will concentrate on the EVAP system.
9. The truck drives fine and has no idle problem. The fuel economy is about 14mgp city and 17mpg highway. That has stayed consistent since it was new. It now has about 170000 miles. THe o2 sensors pass diag but have never been replaced.
10. On a internet search I found a tech bulletin 1205 about o rings on the intake but I think this is the X engine SOHC and not the E ohv.
Any suggestions would be appreciated.
Engine is 4.0 E OHV in Explorer Sport 1999.
1. MAF sensor cleaned. I have monitored this sensor with a scan tool and the output seems normal.
2. The vacumn system has been checked, visual and some parts like egr diagram checked with vacumn pump, all seems good.
3. The only hard symptom is when the computer is reset and a drive cycle is performed the EVAP Monitor test fails and the P0171 and P0174 are diaplayed. I dont know if the test fails because the codes appear or it is the source of the codes.
4. The air filter and fuel filter are fairly new. The fuel pressure is going to be checked but my gague has a larger connector than the value on the fuel rail. Will test fuel pressure soon.
5. If you look at the internet for symptoms the #1 is MAF, but that seems normal. The second is vacumn leaks, I have checked all but the EVAP canister. When I pulled a vacumn on the EVAP cannister I could not get a vacumn to hold. THat may be normal if the vent is not closed. I will investigate that and see if the cannister will hold a vacumn.
6. The only other visable is a small rubber host is hanging down at the differntial. I will investigate if that is the tank vent or something else.
7. The long term fuel trim tables are maxed. Since the engine thinks it is lean the fuel table is maxed. The plugs look good as far as color. The plugs are in the normal color (slight yellow), no spots or burning, not extremely white, no oil fouling.
8. Either I have a fuel pressure problem, i.e. too little fuel, or a vacumn leak. Since the EVAP Monitor diag failed I will concentrate on the EVAP system.
9. The truck drives fine and has no idle problem. The fuel economy is about 14mgp city and 17mpg highway. That has stayed consistent since it was new. It now has about 170000 miles. THe o2 sensors pass diag but have never been replaced.
10. On a internet search I found a tech bulletin 1205 about o rings on the intake but I think this is the X engine SOHC and not the E ohv.
Any suggestions would be appreciated.
