check engine light on 91 x

[explorernutt]

i really dont have a whole lot of change in perormance, but i do only get 12-14 mpg. and check engine light comes on after about 10 minutes of running. fuel pressure is 34psi. i went to auto zone and pulled some codes,-79-41-66-41-66... in that order. i replaced the fpr, and 10,000 miles ago replaced the fuel pump. it also has a stinky smell every now and then, like when i run the motor hard. i had the exhaust checked and it is fine. any ideas on what this might be? thanks for the help! :exp:



91 ford exploder. 4" lift, 33" mtr's--jeep eater and craps chevy's

 

[MrShorty]

Somehow looks like an incomplete codes list -- can't positively identify it, but i would guess the 79 is a KOEO code (should have been repeated twice like the other codes), and the other two (41, 66) are CM aka continuous memory codes (Each set of codes is output twice, with a separator pulse between the KOEO and CM codes, see

KOEO 79 would most likely be caused by having the AC switch on while running the KOEO test.

CM 41 is an O2 sensor lean code. CM 66 points to problems with the MAF. Because both the O2 sensor and the MAF are involved in determining proper air/fuel mix, I expect these two codes are related. There are many possible causes. 1st question is, do you also get an O2 sensor or MAF code from the KOER test (make sure the engine/sensor are warmed up before the test)? KOER codes represent hard faults rather than soft/intermittent faults, which means it can be easier to diagnose from the KOER test. Check the wiring between the computer and the O2 sensor and MAF. Then check the fuel pressure.

And for instructions on pulling the codes yourself at home, see www.troublecodes.net/Ford or www.fordfuelinjection.com or any of the other sites with instructions, or your favorite repair manual. The only "tool" you'll need is a paper clip or other substitute for a jumper wire.

 

[explorernutt]

Check engine light

Scanned the codes again while engine was warm. Came out with the same results as listed above. It does idle a wee bit rough. I slammed on the brakes pretty hard the other day, and the engine died. Anyway haven't found anything out yet, any other ideas on what it might be? Thanks for the help. :roll:

 

[Glacier991]

Mr. Shorty is the best of the best on here on these kinds of issues. Heed his advice. You may need to clean the MAF (lots of posts on that here) and possibly may have some remaining 02 sensor issues (lots of posts on sensor operation as well.. the search feature is your friend... this site is LOADED with great osts, and great advice from really good folks like Mr. Shorty!

 

[MrShorty]

SOP is to resolve any KOEO codes first. I wouldn't expect there to be any relation between the 79 and the other codes or your symptoms, but I still would try to eliminate the 79. Make sure the computer can't see power to the AC system (pin 10, I believe).

Once you resolve the KOEO 79, then perform the KOER test (it is normally easier to diagnose codes from the KOER test than from CM). Be sure to follow the instructions carefully (there are several codes that can simply be operator error during the test).