Check Engine Light Only At High Speeds

[Fleeingpepper]

My check engine light doesn't EVER go on when I'm driving around town. Speed limits like 40-45. When I get a little south of town it goes up to 50. If I go 50 for an extended period of time the check engine light goes on, but then goes off after a little bit. Same thing happens on the highway. Anyone had any problems like this?

I'm probably going to Autozone to check the codes IF they can read OBD 1.5, but that's a big IF. Literally

[GP1138]

I'd say EGR - it engages coming down from 50+ miles an hour, I'd get it on my 3400 swap because I blocked off the EGR port, and had no valve on the engine. I'm not sure, mine never turned off until I turned the car off, then it was off until I came back down from cruising speeds again.

[ManicMechanic]

I agree with the above.

[Fleeingpepper]

Coming down from 50+ miles per hour?

Doesn't that mean it would come on when I'm exiting the highway or coming to a stop? Not after going 50 or more? It comes on pretty quick. When I'm getting on a highway it almost always comes on between 50-60 mph.

I could see the EGR being the problem though. Where is the EGR valve so I can check it?

[Crazy K]

it is on the upper drivers side attached to the intake manifold. you can't miss it!

 

 

When I did the 3400 topend swap onto my 95 3100 it did the same thing, until I made an adapter plate that allowed it to work.