Engine light, coming on, then going off(searched)

I have a 96 4.0 with 150k. My engine light will turn on for a couple hours then turn off. everytime the light comes on i can feel it hesitating under light load or at a red light. Everytime i am going to pull the codes the engine light turns off again. what would cause this to happen? i deliver pizzas with it and put on about 80 miles a day. I got it a couple months ago so i dont know the last time anything was replaced. thanks for your help

You might see if your code reader has a "drive test" option - since it sounds like you're getting an intermittent code, you might not catch it all the time with the KOEO or KOER scan. It should still show as a "soft" code (a "soft" code is intermittent or corrected but not erased, a "hard" code is up ALL THE DAMN TIME,) but not all scanners - especially not all HOBBYIST scanners - will show "soft" codes, which is why the drive test.

Failing that, find a buddy with a shop and a code reader he's blown some coin on, and try that - it should catch everything. You can also reset the code (with the scan tool) and try to make it come up again, or just take the "soft" code and trace it to (usually) a wiring fault or (sometimes) an incipient component failure...

5-90

can i pull the codes with the engine light off then?

keithscianna said:

can i pull the codes with the engine light off then?

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Yeah, the engine controller stores the fault code. Since you have a 96 which is OBDII, there will be some engine data stored at the time the fault occured along with the code too.

Ok i just went to autozone and they told me that they pulled multipule misfires and low voltage to my map sensor. Ill get a tune up today but what about the map sensor? thanks,

keithscianna said:

Ok i just went to autozone and they told me that they pulled multipule misfires and low voltage to my map sensor. Ill get a tune up today but what about the map sensor? thanks,

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Check for a vacuum leak, check for dirty electrial connection, replace MAP.

how much is a map?

keithscianna said:

how much is a map?

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Around $40.00 at Napa.

Ok awsome, i am glad it not to much. is there anything elce i should check or replace. what about fluids? when should i change my diff/auto trans fluid?. thanks,

keithscianna said:

Ok awsome, i am glad it not to much. is there anything elce i should check or replace. what about fluids? when should i change my diff/auto trans fluid?. thanks,

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80-90K miles or everytime your offroading in deep water.