Engine shutting down some cylinders

[69Windsor]

I am trying to help a nephew with his 1992 SHO. Here is what I can tell you. It is switching back and forth between running fine and what appears to be shutting off 2 cyclinders. When it goes into this rough running mode, it sets the check engine light. When it switches back to running smoothly, the check engine light goes out. There doesn't seem to be any specific frequency to it doing this. The only thing is that it seems to be doing it more often now. Apparently it has been going on for some time. When it runs smoothly, it seems to be perfect.

I have a OTC 4000 Enhanced Scan tool and I tried to read out any codes, but it does not appear to be setting any. I admit that the EEC system is foreign to me and so I am not working with 100% convidence I am doing everything right. This is my first experience with it.

First question, is it possible for the Check Engine to come on and no code be set? If it is for sure setting a code, can anyone tell me the right way to read it out with my scan tool?

2nd question, is there a limp mode that these engines go into - if so, are there any common causes?

3rd question, any ideas what is going on that it would switch back and forth like that. I am guessing this is a fuel issue with the computer taking some action, but I am totally guessing.

Any help would be greatly appreciated. Thanks in advance for the assistance!!

 

[firebat45]

1, I have no idea what's going on with the scan tool, you should try reading codes out manually with the KOEO and KOER tests (instructions on sho phoenix project).

At least that way you can figure out whether there is a problem with the reader or if there's no codes (there should be if the light is coming on).

2, There is no limp mode besides the DIS limp mode if the SPOUT connector gets disconnected. I don't think that would cause your problems, all it does is retard timing. You can try fiddling with those wires though.

3, For an intermittent problem like that, I bet it's electrical (see above point). There's probably a loose connection or ground somewhere.

 

[frosho]

Bad DIS module. If I were a betting man, I'd put good money on it. This has happened to both of my SHO's with the exact same symptoms you're experiencing. I had a lot of trouble pinpointing it, too. I couldn't figure it out the first time until I swapped out the DIS on a whim. The second time, I knew immediately that it was the same problem. Now I keep spares.

This is what you're looking for:

For checking the codes, you can do it easily without a reader. Just follow the instructions in this link: http://www.shophoenixproject.com/eec/eec.htm.

 

[NEp8ntballer]

check the condition of the spark plug wires.

 

[69Windsor]

I like the DIS suggestion. I will check over the grounds first.

Is there a diagram anywhere of all the grounds to check?

And is there a diagram of the Ignition components for the 1992?

 

[projectSHO89]

DIS module (most likely), coil pack, wires between them.

Those are your choices.

 

[69Windsor]

Just wanted to post a BIGGGGG Thank You to the contributors that posted replies to request for help. It was infact the DIS Module and for only $89.95 for a new module, we were able to get the car back running smoothly.

My Nephew is happy and in Love with his car again!!

We did find a nice document on the DIS System that had a block diagram.
Ford DIS/EDIS "Waste Spark" Ignition System

Thanks again for all the assistance. The DIS Module fixed us right up!!

 

[frosho]

Sweet.

Thanks for that link.

 

[okcoolthnx]

This is happening to me too! Where did you find a new one? Kragen or Autozone stores?

EDIT: Dumb question, I found a bunch. However, I did NOT find ANY new ones for $90. Can you suggest where? Thanks a bunch.

Side note: I replaced the coil earlier today before finding this thread. Should I just keep this chinese replacement or throw the stock motorcraft one back on? Are there any differences in spark power?

 

[Streetrat]

Same problem with mine except sometimes the tact cuts out when it runs rough and if run for too long she starts to smoke (oil from somewhere on exhaust, none normally). shut it off for a few minutes and then have to start with throttle to the floor. then runs fine. still sound like DIS?

 

[frosho]

This is happening to me too! Where did you find a new one? Kragen or Autozone stores?

EDIT: Dumb question, I found a bunch. However, I did NOT find ANY new ones for $90. Can you suggest where? Thanks a bunch.

Side note: I replaced the coil earlier today before finding this thread. Should I just keep this chinese replacement or throw the stock motorcraft one back on? Are there any differences in spark power?

I'd put the Motorcraft coil pack back on and either return the other or keep it as a spare.

Same problem with mine except sometimes the tact cuts out when it runs rough and if run for too long she starts to smoke (oil from somewhere on exhaust, none normally). shut it off for a few minutes and then have to start with throttle to the floor. then runs fine. still sound like DIS?

Pull the trouble codes from the computer. It sounds like a bad cam sensor, but check the codes to be sure. If the cam sensor is fouled from a leaky cam seal, that might explain your smoke as well.