93 EXP with CEL, Codes 157 and 998 | Ford Explorer - Ford Ranger Forums - Serious Explorations

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93 EXP with CEL, Codes 157 and 998


October 17, 2004
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City, State
midlothian, virginia
Year, Model & Trim Level
1993 explorer xlt
I would greatly appreciate any help from you people in this forum. My 1993 Explorer XLT has been running great until the cooler weather arrived and now in the morning after a cold night, when I start it up, the CEL comes on and it idles very roughly. After it warm up, the CEL goes out and it seems to run fairly well. Even after it's warm, it sometimes hesitates at 60 to 70MPH and the engine will even quit but I can easily restart it at that speed. I forgot to mention that early in the morning when the weather is cool or cold, it really smells of raw gas and blows out white smoke until it gets to operating temperature. I pulled the codes with my scanner and the KOEO code is both 157 and 998 and the same for KOER with both these codes showing. I just put a brand new MAF in this vehicle and cleaned the IAC. I have 183,000 miles on the vehicle but it has the original O2 sensors. Could these sensors be causing this situation.

Any help will be greatly appreciated.



Explorer Addict
December 27, 2001
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City, State
Spanish Fork, UT
Year, Model & Trim Level
92 XLT and '87 Bronco II
According to Brooklyn Bay's code list, a 157 can't be a KOEO code. In the PM you sent to me, you indicated you got 111's before the 157, so I would interpret that to mean that you actually got a 111 pass code KOEO, and the 157 is a CM code (and/or a KOER code if you performed the KOER test).

O2 sensors could contribute to these faults, but it seems that usually when I've seen both a CM 157 and a KOER 998 together, the problem was the MAF circuit.

You said that you replaced the MAF. Note that DTC's point to problems in circuits, of which the sensor is only one component. If the fault were in the wiring between the MAF and the PCM, replacing the MAF wouldn't fix the fault. Be sure the wiring is intact.

Recently, someone posted MAF code troubles. They reported back that the problem turned out to be an incorrect replacement MAF from Autozone. I didn't look into the details, but you might verify that you didn't get an incompatible MAF when you replaced it.