So, I just waded thru 244 threads with the search words 'check engine light' to avoid looking like a fool and reposting. I kept the search vague to get more hits, but I didn't find what I was looking for. If this is a topic that's already been discussed, then please feel free to knock me upside the head, and point me to the right thread...

I have a 97 F-350 4X4 with the 5.8L and auto trans, and my problem is this...my check engine light comes on. Not all the time, only when I'm making long drives. Day or night, warm or cold. Usually it comes on about 150 miles into the drive, but sometimes within the first 75. Now, I know what yer all gonna ask, 'What does the code say?' I don't have access to a computer to get that, or I probably wouldn't be here asking y'all. What I'm hoping to get here are some things to try to eliminate possible causes (and I'm sure there's probably 1,000,002 of em)...what I'm thinking is the O2 sensor, but as you'll all soon learn, I'm not a mechanical person. My grandad had a saying...I'm mechanical, everything I touch, I screw up. Well, I'm a subscriber to that philosophy, so I may be way out in left field...

Any suggestions on where to start would be greatly appreciated.

 

I am lacking some information here so I will guess that it is a non California Truck and you have the OBD I system.

That all said you do not need any computer to read your codes and they would be very helpful in your case.

To read your stored codes (CM codes) or check for other types of codes and to run the self test go to one of these links below:

This is good for the KOEO test:
Ford Fuel Injection How To Run a Self-Test

This one is good for the KOER test:
Ford Fuel Injection KOER Test

Or get a code reader, here is a good one.
The EQUUS #3145
http://i54.photobucket.com/albums/g9...CodeReader.jpg

But if I were to guess than I would guess that the EGR valve is not opening when told to do so by the PCM Computer.

 

You are correct in that it is a non-California rig. As for the OBD I system...I'll be durned if I know...

Thanks for the info on self-testing though, I'll get on that at some point today (hopefully) and let ya know what I find out.

 

You were saying you think it was the 02 sensor. Don't buy any parts until you know for sure, because you will spend all your money guessing the problem. Check for codes and double check all wiring. First thing I would do is disconnect the negative battery cable to reset the computer, then drive it to get a fresh set of codes. You may have an old stored code or 2 that is no longer an issue.

 

Read up on pulling the codes and follow the instructs pretty closely. As for clearing codes, you have a code that is occasionally tripping the CEL, note not all codes will trip the CEL. A CEL can come on for many reasons, all it is for is to say 'Hey you need to check something on the motor!' Once you have the codes it will be easier to diagnose the problem, especially since it is a 97 with an electronically controlled transmission. Mileage also helps in diagnoses as an O2 sensor does need to be replaced after a certain mileage, just like spark plugs.

 

Do not disconnect the battery to clear codes as this will make thing worse and harder to find out what is wrong. The only time you disconnect the battery is if you replace a input sensor to the computer.

To clear all your codes just ground the STI wire and when the CEL starts to flash remove the ground and your codes will be gone.

But read your old codes first and write them down and then clear them.

 

Hey guys, thanks for the tips. I was gonna try this, HOWEVER, as is typical here, we are having one of our random out of season snow dumps, and I DO NOT work outside in the snow unless I absolutely have to.

So at this time, I'm standing by to stand by...

 

Here is another reference for pulling codes when you get around to it: EEC IV Self Test hookup
I think that website does a better job of explaining the blink-out sequence than fordfuelinjection.com . Plus, just jumper the STI to the Signal Return wire in the 6 pin diagnostic connector instead of searching all over for a good ground.