"Check Engine" Light Question

I did a search but could not find anything that mimics my problem. Please direct me to an old thread if you know where this has been discussed in the past............

I have a '93 5 speed SC (approx 107k on the odometer). We just drove it about 350 miles round trip to the the Carlisle All Ford meet. It got FANTASTIC gas mileage, even with the 3.73 gears and taching 2200 RPM on the highway.

However, at sustained highway speeds, the check engine light would come on. When we'd stop at a WaWa for a coffee and start it up again, the light would be out. Then, once on the highway again, the CEL would come back on in about 15 miles of travel. It never comes on when I'm driving in the city.

Sometimes, at low speeds, when turning around in a driveway or parking lot, the RPMs drop so much that I pretty much loose the power steering, but the engine never stalls.

Recent Repairs include (within last 10k miles):
new motorcraft coil pack, motorcraft wires, motorcraft plugs, clutch, motor mounts, trans mount, motorcraft Crankshaft position sensor, motorcraft camshaft position sensor, motorcraft water pump, all new motorcraft belts

Thanks for your time!

My suggestion would be to get the vehicle scanned for the codes and start from there. It could be several things, so without the codes it would be a guessing game. The other problems you have may or may not be related to the CEL.

Someone at Carlisle must have a code readere in their toolbox, so yes, get the codes read and diagnose from there. Without the codes, anything else is pure guess work.

Ira

Did you ever get a solution? I am having a similar issue except my check engine light goes on and off but only when cruising.

I've seen old O2 sensors cause that problem. It takes awhile for the CEL to light up and thats when it has failed that sensor. Normally you won't see an issue with the way the car is running because the computer can keep things running good with 1 good sensor.

Just a thought.

Frit

Thanks Frit,

Actually the light goes on just when cruising, not under acceleration or deceleration. Then it goes out and comes back. It's only on occasionally.
I just pulled the car out of winter storage and changed the oil. It was doing something similar last year but I changed the plugs and wires and it cleared up. I only put 5-6000 miles on it last year so I can't imagine it being the plugs or wires again.

Definitely get it scanned; that's the only way to know for sure. My 94 has EGR issues and it causes very similar CEL symptoms to what you are describing. Typically cruising at steady speed for a little while and then letting off triggers my CEL.

Vince

I guess I didn't need to get it scanned. A few days after this last post I was driving with a friend and my HG blew. I just got the motor rebuilt and took a month to fix the vacuum lines becuase the mechanic had no idea what he was doing as far as the vacuum and SC go. Seems to be running good now. Just fired her up and drove her for the 5th thiem this year.
Hopefully I get more than a few days out of it after this repair.

90% IT IS THE O2 sensors. That's exactly what mine did. Also, the PCM has to detect two o2 faults during the run cycle before it will trip the CEL. That is why it takes a while for it to come on.

On pre-OBD-II cars, you can pull codes by grounding the STI (small wire with the test connector under the hood) and then turning on the ignition. It will flash the codes, and you can check them with a Haynes book or the internet. Or I guess here, I have the diagnostic books.

After the rebuild I don't have any check engine lights anymore. I scanned the codes and didn't get anything with O2 sensors. I got a BAP error but that was becasue the mechanic hooked up a vacuum line to the BAP sensor.
I'm still trying to figure out where the line goes but am doing that in another post.
The biggest problem is that when downshifting for a turn then trying to accelerate out of the turn the car stalls sometimes. I don't know if this may be becasue the idle needs to be set up or if I need a tune because the cam shaft got turned for a little more performance.
I haven't taken it on a long drive yet but it does seem sluggish compared to my previous SC but I am remembering back from college. Things always seem better in the past don't they? i'm just going to drive it locally until I get a better eel fro how the car is working.
I'll keep this updated as I find out more.