ford windstar trouble code

[miami man]

our 98 windstar check engine light came on and stayes on so i used a good obd II diagnostic reader on it and on the screen it says two trouble codes found: lean to bank one
and lean to bank two.what does this mean? what do you think i should check first.

no other trouble codes found.

thank you all for your help and has others used obdII scanners before?

[jglutz]

Tighten the gas cap.

[econoaddict]

Actually the gas cap will set evap system codes.

With out the numbers and full description of the codes I would start by checking out the O2 sensors, they will set lean/rich codes.

[FB71]

It is very, very, VERY uncommon for both O2s in both banks to go bad. 98 Windbag is still the old style 3.8L efi, pre-SPI. These engines had a propencity for intake manifold leaks, bad MAF sensors, PCV system leaks, low fuel pressure (caused by restricted fuel filter or weak pump), all of which will cause lean codes in both banks. I worked on many of these while I was a dealer tech.

[jglutz]

^^Doesn't the ECU look for a change in the O2 sensors values and/or rpm's when the canister is purged. If the cannister is purged and no change is detected in the O2 or RPM...the ECU thinks the air/fuel mixture is lean. A loose gas cap would cause no fumes to be stored in the cannister.

[econoaddict]

Your codes?
PO171 and PO174

FB71 hit it on the head, I forgot about those darn intakes on that rig.
Check the stuff he listed first. :thumbup:


jglutz: If the cap is loose you will normally have the code:
PO442 and/or PO455 indicating a small or large leak in the evap system.

[FB71]

^^^ Bingo. Also, all Windbags after 96 have an evaporitive emissions diagnostic monitor. A small or large leak, what ever the source, will set one of the above DTCs. With that DTC present, the PCM will NOT purge the vapor canister.

[FB71]

[QUOTE=jglutz;150281If the cannister is purged and no change is detected in the O2 or RPM...the ECU thinks the air/fuel mixture is lean.[/QUOTE]

No, the PCM is smart enought to know that it's introducing unmetered air, and will just shut down canister purge when it sees a lean condition. That's how the PCM determines how much fuel vapor has been stored. It watches for the O2s to first read a bit rich, stabilize, then go lean. Once it goes lean, it knows the canister is empty, and shuts off the purge.