Check Engine light is on, help!

[Mainfraim]

Right after we changed the spark plugs in our '91 Explorer, the Check Engine light comes on when you put it in gear. While I don't know if the Check Engine light is a big deal, it kind of bothers me. If anyone could help me figure out what's up, I'd appreciate it. Thanks.

 

[Triton46]

Mainfraim,

Ive seen this many a time myself. The most likely culprit is your O2 sensor, however this could also be a bigger problem if you are having mileage and power problems. Many 91's and 92's have there Fuel Pressure Regulator go out around 100k. I changed my FPR out only to have the Check Engine come on again, changed my O2 sensor and it came on once but seems to be gone now.

I would suggest checking your engine code. It is very easy to do with the 91's. You simply have to jumper (with a wire or paper clip) two slots in your Onboard Diagnostic, turn the key to on (dont start car) and count the number of times the Check Engine light blinks. Thats it! I did this after changing the two parts mentioned and my code pointed that the O2 sensor is not present, possibly a bad connection (I will have Ford check). If you need more detail or what the codes are let me know and I will write down whats in my Haynes manual.

[Edited by Triton46 on 10-29-2000 at 05:44 PM]

 

[Cameron]

The first thing you should try is to disconnect the battery for about 10 min. Let the codes clear from the ECU. Then, reconnect the battery and start the motor again and see if you get the check engine light. If not, cool. If you do, diagnostics are in order.

 

[Mainfraim]

Well, I messed around with all of the wires that could have been touched when we did it, tried to see if anything was disconnected, and it didn't seem like it, but something did the trick. It went away. Don't know what did it, but it's gone. The onboard diagnostics, clicking, check thing is kind of cool though, I'll have to keep that in mind. It seemed a little big luggy right before I fixed it too. So all is well I guess. Thanks for your help guys.

 

[Triton46]

Mainfraim

The code will still be in memory (ie you dont have to check it right when the code appears). I would check just to make sure.

Also, do not unplug the battery for 10 min. This resets your computer to default (as it came from the factory) during which time your truck will run like crap while it relearns its parameters then the code will reappear. This is not the best way to erase codes. When checking your codes with the jumper method, you disconnect the wire at a certain point and your error codes will be erased without resetting to default. Hope this helps.



[Edited by Triton46 on 10-30-2000 at 07:37 AM]

 

[Cameron]

Respectfully I disagree with Triton46. It is very common practice to clear the ECU of error messages to see if it was a "fluke" prior to performing diagnostic checks on the system. Additionally, whenever you add a new component to your truck, such as a new throttle body, you want to reset the ECU so it can re-learn the new system. And lastly, in all the times I have done this, my truck never drove poorly afterwards. The ECU will pick up new changes within seconds. It's not unlike disconnecting your battery whenever your working on the electrical system. You're inadvertently clearing the ECU. We have all (at least most of us have) done this many times. It is the proper way to ensure there is a "real" problem.

 

[BIG-B]

question

Originally posted by Triton46
Mainfraim,

Ive seen this many a time myself. The most likely culprit is your O2 sensor, however this could also be a bigger problem if you are having mileage and power problems. Many 91's and 92's have there Fuel Pressure Regulator go out around 100k. I changed my FPR out only to have the Check Engine come on again, changed my O2 sensor and it came on once but seems to be gone now.

I would suggest checking your engine code. It is very easy to do with the 91's. You simply have to jumper (with a wire or paper clip) two slots in your Onboard Diagnostic, turn the key to on (dont start car) and count the number of times the Check Engine light blinks. Thats it! I did this after changing the two parts mentioned and my code pointed that the O2 sensor is not present, possibly a bad connection (I will have Ford check). If you need more detail or what the codes are let me know and I will write down whats in my Haynes manual.

[Edited by Triton46 on 10-29-2000 at 05:44 PM]

i have a 91 sport and check engine light comes only in certain gears at certain rpm and at idle speed i want to know if you know or heard anything like this ???? help please

 

[Triton46]

Do you have a manual or automatic transmission? I have the manual and am getting a check engine for a transmission sensor as well. Ford says not to worry unless I begin having problems shifting, however, if I kick into neutral before I stop or turn sometime this will set off my check engine.

 

[Triton46]

And she's off again...went home this weekend (360 round trip miles) with no Check Engine. I guess its fixed...for now.