Check Engine comes on when driving 65+ mph sustained

[Svgess]

Howdy folks. I have a 2004 Sport Trac and I just had the harmonic balancer replaced after it died on the freeway. It now works fine around town, pre-existing squeal is gone too. When I took it on the highway, the check engine light came on and the engine started running poorly, then the light went off and back to normal. It happened several times and seemed to be a pattern so I timed each instance. It would be on for ~35 seconds and then off for ~2 mins. It did this the entire time that the engine was above 2k rpms for any sustained length of time. Once I realized the pattern and reduced my speed, keeping it under 2k, it completely stopped. Is this a sensor issue or something simple that can be done like resetting the ECU or do I need to take it to the shop that replaced the balancer? Trouble is, the shop is on the other side of Atlanta (over an hour away) and its a bit of an operation to make the trek, especially if they are going to be keeping it overnight.

Thanks in advance

 

[curtis james]

ya mentioned it all started with freeway driving, it died. how was it acting prior to that incident. have not heard of a harmonic balancer instantly going out like that, they will squeak and cause a vibration. the higher the rpms the faster revolutions will cause it to do what you mentioned. you should look at engine and rev it up and look at belts and see if all is moving smoothly and see if it starts vibrating. maybe a bad balancer got installed.

 

[Steve Brothers]

Maybe this is an unrelated issue to your harmonic balancer. Might be a fuel delivery issue at higher fuel demand. Fuel filter or maybe fuel pump. Also if the evaporative fuel system is not working correctly, you can get a vacuum in the tank, reducing fuel flow.

 

[blert]

Um.. what's the code?