1992 Explorer CEL questions

[Redandwhitebrit]

I have a 92 Explorer with 190,000 miles that has been running very well until this week. The check engine light has come on and when the codes were pulled I got 172 and 173. These are run lean condition and run rich condition. The CEL is on intermittent and mostly stays off in city driving, and stays on constant at freeway speeds. I am at a loss as where to start, the MAF is clean, no fuel present in the vacuum hose at the fuel pressure regulator. I have not checked fuel pressure. Any suggustions would be appreciated.

 

[MrShorty]

By the book, one is supposed to start diagnosing O2 sensor codes by checking fuel pressure.

Can I assume those are CM codes? Did you get a 111 pass code from the KOEO section? What do you get from the KEOR test? If you clear CM, do you get the same pair of codes back, or do you get one or the other?

 

[Redandwhitebrit]

Fuel pressure was checked this morning and is all within spec until the key is turned off. With the engine off, the pressure drops rapidly to less than ten lbs. Any ideas?

 

[MrShorty]

If the FPR is at fault here, it would probably be due to a leaky diaphragm. Have you checked the vacuum line to the FPR for gas (gas=bad FPR)?

I still would like to know the answers to the other questions (KOEO/KOER codes, do these same codes come back etc.). If you need help understanding these acronyms or how to perform these tests, review my "notes on pulling EEC-IV codes" thread and the other instructional threads for getting EEc-IV codes. Just want to get a complete picture of what the computer is trying to tell us.

 

[Redandwhitebrit]

All tests were taking me nowhere until the FPR suddenly spiked to 90+ lbs. while idling in the garage. This happened after I pulled a vacuum on the line with little change in fuel pressure. It appears that the FPR was intermittent with a problem. I changed it out and the test drive was very good, no codes, car runs very well, and the rain stopped in middle Tennessee. Must have been a bad FPR all along. Thanks for the input to my problem.
Regards,

 

[MrShorty]

That sounds promising. Let's hope that resolves it.

 

[Redandwhitebrit]

I just finished a 1200 mile trip to Florida in the 1992 Explorer, and turned over 190,000 miles with zero problems. The new FPR solved all of the fuel mileage, performance, CEL, problems.