Rough Idle/CEL

[wifd552]

Hello all. I have been having trouble with a rough idle and CEL on my '93 explorer. Pulled the codes as per Mr Shorty's write-up and got the following KOEO 111 and CM 157, KOER revealed 998 and 157. As per my reasearch, 111 is a pass, 157 is MAF "is/was" out of range and 998 KOER is a hard fault and it did not even run all the tests because it recognized a KOEO code. So far I have cleaned the MAF and IAC valve, also replaced the vacuum modulator on the transmission. I have been getting a fuel smell under the hood and some white smoke out the exhaust. The rough idle changed slightly after I cleaned the IAC valve. Any ideas? Help is greatly appreciated. Also, does anyone know of a way to diagnose the MAF, other than checking voltage? I would like to be able to fool the computer while disconnecting the sensor to pinpoint the problem.

 

[MrShorty]

Interesting problem. Sounds very similar to a couple others that have been talked about in the last few months. go down in this forum to a thread with a title something like "unknown code" talking, initally, about a 999 code (ended up being a 998 code with an accompanying MAF code). As I recall, he ended up bagging the process of diagnosing the problem and just replaced the MAF and found that that fixed his problem.

I can't off hand think of a good way of testing an MAF without measuring the output voltage in some way. I suppose there's the guess and check kind of thing (install a known good MAF and see if that resolves the problem), but the point of a diagnostic process is to usually avoid guessing and checking.

 

[RN]

Does anyone know why th idle cannot be changed on a Ford Ranger 2000 with the 4.0 OHV engine. Warm idle at 980, all codes normal, dealer claims this cannot be lowered.

RN