Just bought my first real truck ('93 F150) a few months ago and have been fixing up the few small problems that it had one by one but i wanted some input on this issue before i go and let the dealership bleed my dry trying different possible solutions.

Anyways, when i drive the truck at expressway speeds for 45 minutes or more the check engine light comes on, sometimes it stays on for a while, sometimes it goes off after a few minutes, either way it then comes and goes seemingly at random for the remainder of that drive (if i stop and shut it down for 30 minutes or more i can then get it another 45 minutes or so down the road b4 it starts coming back on/off/on/off/etc...). The engine seems to be running fine but i have this darn check light going on and off annoying me and making me worry that something might be wrong with my truck. Anyone got any ideas as to what might be likely to cause the light to go on and off like that? The truck has 155,000 miles on it and is in pretty good shape overall. I eagerly await your thoughts on this matter.

Thanks!


wolf189
************************************************** ***********************
'93 F150 4x4 Regular Cab, Long Bed - 4.9L I6 w/5spd Manual
no mods... yet...

 

I have a 92 4.9 5 speed. I have owned it for 2 years this summer.
The only time i have saw the engine light come on is when the back fuel pump started going out.When i switched to the front tank light went out.
Have you checked the computer for fault codes?

 

Go buy a code reader and pull the codes. You can get one at the parts store or maybe even walmart for around $30. You can actually pull the codes with a piece of wire and a test light. The reader makes hookup easier and the book that comes with it and lists all the codes is well worth the money.

 

Mine does the same thing every now and then, and I've concluded that theirs a sensor going bad or shorting out now and then. If you don't get any error codes, then I wouldn't worry about it.

TrailDawg
https://www.ford-trucks.com/dcforum/User_files/3aaa4bac6f539876.jpg
1993 F150 2WD
4.9L-Auto
Pro-Comp Stage-2 6" lift
Auburn Pro-Series Diff. w/4.30:1 gears
35x12.50x15 General Grabber MT's
http://www.geocities.com/ProjectTrailDawg

 

>Go buy a code reader and pull the codes. You can get one at
>the parts store or maybe even walmart for around $30. You can
>actually pull the codes with a piece of wire and a test light.
>The reader makes hookup easier and the book that comes with it
>and lists all the codes is well worth the money.

Yeah, i guess i really should go get a code reader to see what i can find out from that before handing the truck over to the dealership (or anywhere else either for that matter) and letting them start guessing at the problem.

Thanks for the input folks, i'll let you know when i figure out what's causing the light.


wolf189
************************************************** ***********************
'93 F150 4x4 Regular Cab, Long Bed - 4.9L I6 w/5spd Manual
no mods... yet...

 

wolf189:

Just to ease your mind about the "check engine" light. It's telling you that an "emmissions" problem is occuring. Your engine is not going to blow up or anything.

My wife's 96 merc cougar had the check engine light going off and on for 2 years before i decided to let the dealer fix it and empty my wallet at the same time. They reassured me that on the OBDII setup it's always emmissions related. I'm not sure if your truck is OBDII or not but it is most likely a sensor thats going bad. Like the other posts above, try to get the code and take it from there.

My hunch is that you have a bad O2 sensor. good luck!

1981 F-150 2WD STYLESIDE P/U
4.9L 1 BBL CARB
C6 AUTO
2.73:1 LIMITED SLIP REAR AXLE
STABILIZER BARS FRONT & REAR
6100 LB GVWR PACKAGE
ORIGINAL OWNER
195,700 PLUS MILES
100% STOCK & UNREBUILT
BUILT FORD TOUGH!!!

 

check MAP sensor.