Real bad spark knock, then Service light?

[Mike Zarnock]

I have a 91 Coupe that will spark knock real bad when warm. When it does, the "Service Engine" light will come on. The car will loose power, like you have the break on. You have to pull over and stop. If you turn it off and restart it, the light will go off and it will run fine for a while. It will not throw a code when checked.
I have changed the fuel filter, ignition modual, plugs, cap, rotor and use the best fuel I can find. The advance is working fine when checked at all times.
The only thing I have not changed that I can think of is the coil. Could it be breaking down when it gets hot? Is there something I missed? Is this common?
I'm going nutz! I hate all this computer junk!!!!!
PLEASE HELP!!!!!
Mike

 

[LT4man]

If the "Service Engine Soon" lite comes on, then a code has been set.

Could be that your scan tool is not communicating properly with your ECM.

Once you get that sorted out, diagnosis becomes easier.

SAVE THE WAVE!

 

[Mike Zarnock]

I left it at the shop, (since I do not mess with this computer sh#t). They did the tests, they drove it got it to do it and still no code.....
Maybe another shop?

 

[larry bud]

I have a 91 Coupe that will spark knock real bad when warm. When it does, the "Service Engine" light will come on. The car will loose power, like you have the break on. You have to pull over and stop. If you turn it off and restart it, the light will go off and it will run fine for a while. It will not throw a code when checked.
I have changed the fuel filter, ignition modual, plugs, cap, rotor and use the best fuel I can find. The advance is working fine when checked at all times.
The only thing I have not changed that I can think of is the coil. Could it be breaking down when it gets hot? Is there something I missed? Is this common?
I'm going nutz! I hate all this computer junk!!!!!
PLEASE HELP!!!!!
Mike

IMO, the "computer junk" makes it EASIER to fix since you don't have to guess. Get a Helm manual, read the code, and follow the diagnostic flow chart in the manual.

 

[G Winter]

When you pull over and restart it do you wait just a bit giving engine a chance to cool some? And does it loose power very soon after that?
Sounds a lot like plugged catalytic convertor.

Glenn

 

[Mike Zarnock]

When you pull over and restart it do you wait just a bit giving engine a chance to cool some? And does it loose power very soon after that?
Glenn

No, I have gotten so good at it that I can throw the car in neutral while I am still going, turn it off, then restart it and go.
I have also had another shop look at it and came up with the same thing, there are a lot of things that "MAY" be causing the light to come on.