OBD-IV Code Reader Mystery

[lowmon]

Interesting series of events '91 Explorer. Has been runnig fine until I pulled off the freeway the other day. The motor started knocking, shaking rough, with just enough power left over I was able to get it off the road. The following day i showed up to give the Ex a tow. It started up normal, drove a couple circles, Normal. so we took the chance to drive it easily. But same syptoms came up two miles later and the tow was on to home.
I put a Code reader on and it reported a 4 cylinder motor. I disconnected the battery for a while and it returned a 6 cylinder motor. Bad ECM?...... I am just at the beginning of diagnosing what could be anything from a filter to a timing chain tensioner as found in these threads.

 

[BrooklynBay]

Welcome to this forum! Did you get any other error codes? What code numbers came up when you scanned it? # 17 in my list of useful threads has information on 2, and 3 digit EEC-IV codes: http://www.explorerforum.com/forums/showthread.php?t=160035

 

[Alan_V]

Interesting series of events '91 Explorer. Has been runnig fine until I pulled off the freeway the other day. The motor started knocking, shaking rough, with just enough power left over I was able to get it off the road. The following day i showed up to give the Ex a tow. It started up normal, drove a couple circles, Normal. so we took the chance to drive it easily. But same syptoms came up two miles later and the tow was on to home.
I put a Code reader on and it reported a 4 cylinder motor. I disconnected the battery for a while and it returned a 6 cylinder motor. Bad ECM?...... I am just at the beginning of diagnosing what could be anything from a filter to a timing chain tensioner as found in these threads.

Is it a code reader you've used before and can trust? For me, that's the first thing I want to find out. That said, a scrambled PCM can do anything, really.

 

[lowmon]

Sorry I didn't get back right away. My schedule keeps me busy. today I ran the code reader on the ex. KOEO set continuous memory code 95. KOER sees 6 cylinders, at code 10 I am instructed to give a WOT to reader. Suddenly runs like a jalopy. Shut off engine then redid KOER, now the reader sees 4 cylinder motor. It seems to me this is bad Control Module.

 

[Alan_V]

Sorry I didn't get back right away. My schedule keeps me busy. today I ran the code reader on the ex. KOEO set continuous memory code 95. KOER sees 6 cylinders, at code 10 I am instructed to give a WOT to reader. Suddenly runs like a jalopy. Shut off engine then redid KOER, now the reader sees 4 cylinder motor. It seems to me this is bad Control Module.

well, it's one of 2 things for me.
Yes, it's a bed ECM.
BUT!!!! What happens if you don't go WOT? Will it stay at 6 cyl, or does it ever change? If you let it sit after it changes to 4 cyls, does it ever go back to 6??

I'm concerned that what you are seeing is not info from the ECM, but an interpretation from the scan tool. It's only seeing 4 cyls firing , so it's a 4 banger. And while I don't know Ford ECMs at all, what I am familiar with won't ever do that.

Do you know the history? Has it maybe been chipped with a programmable PROM?

Then again, I'm known for overthinking things.

 

[lowmon]

Thanks for the reply Alan_V I tend to overthink things myself. The events with the ex prior to my last post were the same engine response without any excessive acceleration. In fact I was babying the ex just to see if it would drive a good distance without any issues. Under those conditions I had the same jerks and clatter but long from home had no idea of the cause prior to diagnostics under the reader. It is a good reader with fresh batteries that I have used in the past. Now just a matter of pluggin in replacement ECM and seeing what happens.

 

[lowmon]

mystery solved. In back tracking to the coil pack I found that the harness connector to the coil was without its anchor clip. This had to have occurred during previous ownership. Through torque and vibrations the connector had backed off enough to stop the ignition module from signaling for spark. A couple of zip ties took care of it. Now runs fine.Hooray.

 

[BrooklynBay]

Thanks for the update!

 

[Four0Sport]

gotta love easy fixes. did you pack any dielectric grease into that connector, the grease also helps prongs from backing out. just an idea. i knew a guy once that had a clip break off his connector and it would ALWAYS slide off while driving so he red loctited the connector, scary stuff.