93 Exp with KOER 157 & 998

[bfsjr]

My 1993 Ford Explorer is sluggish when starting now that the weather has gotten colder and the CEL comes on and stays on until the engine gets warmed up and then the CEL will go out. Once the engine is warm, it feels like it is missing on one cylinder. I have replaced the IAC, ECT, coilpack, MAF, new plugs and wires, and it still does the same thing during startup in cold weather. I pulled the codes with an Actron Scanner and the KOER codes are 157 and 998. I wired the new MAF just like the original so I don't think the problem is the MAF since the CEL goes out when the engine is warm.

When I pull the spark plug wires off the coilpack one at a time, the only plug wire that when pulled has no affect on the missing engine is the #2 cylinder plug wire. I have checked for a vacuum leak and found none. The fuel pump is also new as is the FPR. I even tried a another computer but the results are the same.

I haven't run seafoam through the throtte body yet so could this possibly be a sticking valve. The engine has only about 35,000 miles on it.

Any input would be greatly appreciated.

 

[cjones101812]

the code 998 means you are in 'limp home' mode.

clear codes, run engine at idle for 10 minutes, rerun for codes. do they reappear??

 

[MrShorty]

Remember that codes point to problems in circuits, not just sensors. Are you certain the wiring between the PCM and the MAF is good? MAF getting power and ground for the "excitation circuit"?

 

[bfsjr]

I have not repulled the codes but again today, when I started the 93 EXP it was sluggish and missing as usual with the CEL coming on, as usual. After it warmed up, the CEL went out and the only unusual thing was the slight missing in the engine. You can barely feel the miss but it's there. It seems that it is missing on only one cylinder. I have checked and checked for a vacuum leak but have not found one.

I have also checked the wiring from the MAF to the PCM but I don't find any breaks. I even took the MAF off today and cleaned it but the miss is still there in the engine.

I did notice that the plastic cooling fan looks to be the original and it has cracks at every blade at the hub. These cracks run the entire width of each fan blade. When the engine is idling, I can see that the fan seems to wobble a little. Could this cause the missing feeling in the engine that I am feeling. I am definitely going to have to replace the fan due to the deep breaks but I am concerned as to whether this can make the engine feel like it's missing.

Thanking you in advance for responding to my thread.

 

[bfsjr]

93 Exp with KOER 157 & 998

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I have not repulled the codes but again today, when I started the 93 EXP it was sluggish and missing as usual with the CEL coming on, as usual. After it warmed up, the CEL went out and the only unusual thing was the slight missing in the engine. You can barely feel the miss but it's there. It seems that it is missing on only one cylinder. I have checked and checked for a vacuum leak but have not found one.

I have also checked the wiring from the MAF to the PCM but I don't find any breaks. I even took the MAF off today and cleaned it but the miss is still there in the engine.

I did notice that the plastic cooling fan looks to be the original and it has cracks at every blade at the hub. These cracks run the entire width of each fan blade. When the engine is idling, I can see that the fan seems to wobble a little. Could this cause the missing feeling in the engine that I am feeling. I am definitely going to have to replace the fan due to the deep breaks but I am concerned as to whether this can make the engine feel like it's missing.

Thanking you in advance for responding to my thread.

 

[MrShorty]

If the fan is out of balance, it could cause the engine to vibrate, but that wouldn't explain much else.

Do you get an MAF code from the KOEO test and/or in CM, too?

Does the MAF have power from the EEC-relay? Does the MAF have a good connection to ground? What voltage do you get at the PCM for the MAF signal?

 

[cjones101812]

do you have a scanner?? if so, check the IAT (Intake Air Temp) and ECT (Engine Coolant Temp) sensors. see what they are reading when the engine is cold.

please rerun the codes (part of the diagnostics).

#2 cyl miss, have you checked the plug?? have you checked for injector pulse??

when you checked the wiring. you did an Ohms check on each wire, with both connectors disconnected, correct?? MAF is A,B,C,D; ecm is #s.

A to Pin#s 37 & 57; B to Pin#s 40 & 60; C to Pin# 15; D to Pin# 14.

 

[Dragon90815]

Change the MAF I have the same codes 157 & 998 on a 93 exp xl.

code 998 = car is operating in Failure mode because 157 your MAF has low voltage on pin C of your MAF. if you back probe pin C and is reading below 1v while engine on. then test pin C with Engine off Key on disconnected from MAF it should read about 5 V on the cable side (if it is like this change MAF) (if no voltage on pin c with cable disconnected and Key on then it's the ECM)