1992 F150 4.9 6 Cyl
 

Recently bought this truck for work purposes. Ive noticed check enigine light comes on when accelerated hard such as merging on to freeway or going up hill but will come off by itself after few minutes. Any ideas/suggestions as to what might be the culprit?

Check the codes stored by the ECM first. Even without the CEL being on, you can have codes that could help find the problem.

My first guesses would be O2 sensor out of range or EGR flow out of range, but it could be any number of things. First step is pull the codes and get a direction from there.

You can read up on how to read codes manually through your check engine light, or you can get one of these:



The code will be stored in the computer even if the light is off.

Get the ability to read codes (just too easy), but on a carb'ed motor the classic fault causing problems under heavy load is a partially clogged fuel filter causing fuel pressure at the engine to drop. When the load goes away, proper fuel pressure returns and the light goes out.

From what I've been reading on this site, the CEL only comes on for emission related problems. As stated above, pull codes, that will point in the right direction.