CEL flashes then stays on goes out after about 50 miles

[mountainmusic01]

First, I want to say hello to evryone and this is really nice to find something like this. I own a subaru legacy LS 1996 with 98,508 miles the car runs great as long as you don't go on the highway. once yo reach the spped of 62 mph its starts to stumble CEL falshes aftes it stops flashing and stays on the car regains normal running and it dosn't happen again until after 50 miles the CEL goes out and the same thing. put new plugs samething. Plug into the ecu and reads missfire cyl 3 I don't understand how this can happen at the same speed and rpm every time any help would be appriciated thanks mick

[rudgers73]

sounds like bad o2 sensor or cat

[harrymaneuvers]

How would that cause a misfire in cylinder 3????

If it is only happening on 1 cylinder... I would be suspect of your spark plug wire... or the injector on that cylinder.

Its also interesting to note that the problem seems to "cure" itself once the CEL comes on... and then starts up again once the light turns off.

Maybe note what RPM it happens at when you reach 62 MPH on the freeway and see if you can recreate the issue by reving the engine while the car is parked or in neutral.

Also... Make sure that you are always getting the same CEL code for the same cylinder each time you have this issue.

When you are cruising down the freeway and the light comes on... what would happen if you pulled over and turned off your car then restarted?? Would the CEL remain lit or would it be off until you got up to 62 MPH again?

[mountainmusic01]

as soon as I det on the exit ramp and get up to 62-63 mph it stumbles the cel flashes and as I back off acc. and the light stays on instead of flashing I can continue with the car running normal get back home and the kight stays on no mater how manty times I stop and start it just drive it aroond town runs great then light goes out and we start all over!!! frustrating

[evolegacy]

I gotta agree with Harry, sounds like a bad plug or injector, could even be the wire itself. plugs are cheap so I say just swap them out and see how things go from there. If money is tight pull the plug out of #3 and check for oil or scorch marks, and check the gap on it as well, should be around .41 if I remember correctly.

[ouch1011]

Of all the misfire codes/rough running concerns I see, I'd say 80% of them are caused by ignition system problems. Usually spark plugs or plug wires. I saw you put in new plugs already, what about the spark plug wires? I'd also pull the #3 spark plug wire off at the coil and check the connection there for corrosion. That's pretty common as well.

[harrymaneuvers]

Hopefully all of the codes you get are on cylinder 3 and not bouncing from cylinder to cylinder.

[Huffer]

Actually if you swap the plug wires and the code shifted to another cylinder, you can isolate the plug wire as the problem.

[harrymaneuvers]

Same thing with the injector on that cylinder.