P1131 code Fuel Acturer control - Fuel air metering
In almost every Ford Product from 1990 to 1999 the most likely cause is the Mass Air Flow (MAF) Sensor.
Auto manufacturers have a cleaning cycle built into the MAF circuit. How it works is this; when the key is turned off a larger current is sent through this hot wire causing it to glow red hot, thus burning off any contaminants. Well, almost all auto manufacturers that is.
MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.
To confirm this disconnect the MAF sensor connector. This puts the vehicle into Failure Mode and Effects Management (FMEM). In FMEM mode, airflow is inferred by using rpm and throttle position instead of reading the MAF sensor. (In addition, the BARO value is reset to a base/unlearned value.) If the lean driveability symptoms go away, the MAF sensor is probably contaminated and should be replaced. If the lean driveability symptoms do not go away the MAF sensor is probably not contaminated.
When this happens Ford says you must replace the MAF since they cannot be repaired. With a dealer cost of about $177.00 and about 1.5 hours of labor the repair is not very expensive. However Ford is not correct. This problem can be fixed and it can be done by just about anyone.
What you need to do is go to the local Radio Shack and get a can of spray tuner cleaner, #64-4315. Or a MAF cleaner at any Auto Parts store. Disconnect the NEGATIVE battery cable and remove the MAF from the vehicle. Spray the inside of the MAF with the tuner cleaner. Be very careful when you spray the hot wire. It is very thin and if it breaks, you will have to replace the MAF. Clean it well and let it air dry for 15 or 20 minutes.
Don't use carburetor or brake cleaner. They leave a residue and you will be right back where you started. Use ONLY the tuner cleaner, MAF cleaner which dries residue free. When it's dry put it back in the vehicle and reconnect the NEGATIVE battery cable. You will need to drive the vehicle several miles to let the PCM "relearn" your specific driving conditions. Once that is done the codes will not come back and you should notice all the symptoms are gone as well.
Good luck and keep me posted, be glad to help you get your car running 100% soon.
Sep 02, 2009 |
1997 Ford Escort