What's going on here?

The check engine light, comes on if I drive for approx. 25 minutes at highway speeds.

If I stop and restart the motor the check engine light goes out.

The motor seems to be running great with oil, water, etc in the normal range.

Any help or suggestions appreciated.

1994, F-250, 351, 2 wheel drive.

Thanks In Advance

Davie
Vancouver BC.

 

My mother has a 96 Aerostar Sport that has a problem with the check engine light coming on too ... it just stays on all the time! It started after the battery had died a few months ago ... it's been to the shop and everything and there's nothing wrong with it ... it just stays on all the time. Any ideas why while we're on the subject?

Chris in Canada
74 Gran Torino Brougham ... the toy ... older and wiser.
84 F150 2WD ... the truck ... wife says, "never trust a teenager."

 

Not enough info. Some guesses...

A 94 probably has a fair amount of miles on it. If I had to take a shot sight unseen, I would guess the EGR is starting to stick or an O2 sensor is starting to get a little flakey. Could be other things too, but that has been my experience, not on a Ford Truck however. Some Ford EGR valves have a little window to allow you to clean the mechanism out, you might try cleaning it with some throttle body cleaner, or maybe some carb cleaner(O2 sensor safe types only).

The emissions control computer is probably detecting something starting to go bad in one of the sensors. When you stop the engine, it will reset and won't come on again unless the sensor detects another slightly out of spec condition. Once the sensor detects a way out of spec or complete failure, the light should come on all the time.

I would take the car to the dealer and have them read the code from the diagnostic port. You should also be able to buy a simple decoder at a local autoparts store. Usually a flashing light decoder. Easy to use and at least on one occasion it told me to fix something cheap while the Ford dealer charged me big bucks to fix something else which didn't fix the problem. The cheap fix was the solution, that was an EGR.

Hope this helps.

Jim Henderson

 

I had a check engine light problem too> HAd the codes read for a "Buy me a beer when..." said it was egr not opening, I don't have any wizzy tools just a multi meter. I put external vaccuum(by a hose to the plenum tree) to the egr while running and it opened up making the engine run crappy, so it's ok.A resistance test on the sender proved it ok too. I then took the solinoid up by the ign coil off and took it appart. Found it was filthy. The disk valve was being held open by dirt on the valve seat. Cleaned it and re-assembled it , tested the coil ,it's ok. Hooked it all back up and every thing is fine now, now more lights. Took an hour of my time and cost nothing. Can't beat that.

 

Appreciate the responses
Hmm' seems like the egr valve would be the starting point.
Now, where did I leave that manual?

Thanks again

Davie.
Vancouver BC.

 

My 1996 F150 had the same thing. I had it at the dealer 3 times. It was a faulty O2 sensor in the exaust that would trip the light. Repleace the sensor, problem solved.