'91 Ex barely runs, no power

[dnoot]

I'm new to this forum and have learned a lot. Have searched and seen similar issues posted, but not the same. Hoping someone can point me in the right direction. (I apologize for the long post - trying to provide details ;-)

For the last 1000 kms or so, I was getting the best mileage I've ever got, 3-4 MPG better than normal. Then from one day to the next, my '91 Explorer (2WD, auto, 230K kms) crapped out.

Here's what's happening:

• starts OK, but the idle is really rough (like it's seriously missing)
• stalls after 10 - 20 seconds
• CEL comes on after a while, but doesn't stay on (i.e. it's off when I restart)
• throttle response is very poor - very difficult to get revs up
• smoothes out somewhat at higher rpm, but still rough and sounds like its "barking"
• no power - stalls as soon as I put it in gear (with throttle at idle or pressed a bit)
• rpm reading on tach *seems* low for the engine sound
• when revving up to 2000 rpm or so, occasionally the revs jump (and engine smoothes out) for a second, then reverts to crap
• unplugging MAF sensor makes no difference
• swapped MAF with another used unit - no difference
• my mechanic says it's running lean, but when I struggled to keep it going today, it smelled to me to be running rich

Had it towed to my mechanic, but he had trouble reading the codes on two different devices. So I went over and tried to read the codes based on instructions posted here (jumped to ground and read CEL). Unfortunately, I didn't do the break pedal / steering wheel (?) / mash throttle during KOER, so what I got is not likely useful. (Can someone please point me to complete instructions, including timing of the user inputs, during KOER?)

KOEO
Some initial rapid flashes, then
--> 1-1-1, repeated
--> long break, 1, short break (not proper timing for separator?!?)

CM
If I assume the 1 above was the separator,
--> 2-3-2, repeated
If this is right, thorssell.net says "232 (M) EI primary coil circuit failure"
Some other on-line code lists do not include 232.

KOER (again, no user inputs)
flashed 1-1-1, then after a minute or so, tons of flashing all over, and the spacing didn't seem proper. I tried to grasp something: perhaps 1-5; 1-6; 1-7; 2-4.

Any ideas?

One other odd thing, likely unrelated: the +12V lead to charge the battery on a holiday trailer is not working properly (it was fine last season). Oddly, it reads 12V at the truck connector, but when I plug my trailer in, it drops to about 5V (even when reading on the trailer connector with the trailer +12 wire disconnected). Everything else is working fine (lights & trailer brakes). I've spent a fair amount of time tracing wiring, re-doing grounds, checking fuses, etc... all looks fine on both the truck & trailer.

Thanks in advance for any assistance!
Don

PS - just went through similar issues with my '90 Volvo 240DL although the rough running was intermittent. Turned out to be the ECU - diagnosed through a forum! Was cursing that car and pointing to my trusty Explorer as a great vehicle that's never let me down... DOH!

 

[MrShorty]

When I wrote my "notes on pulling EEC-IV codes" (in the EEC-IV forum), I was hoping it would help people understand how to properly perform the tests. I'm curious which parts don't make sense.

Are you sure you're getting three digit codes? A '91 model year normally should be outputting 2 digit codes. It's always possible a '92 computer snuck in just before the end of the '91 production run, or someone has swapped computers after the fact. It's also possible that you have a '92 model year built in '91. In any case, I would double check that to make sure you're counting the pulses correctly.

Assuming a '91 with 2 digit codes, I would expect to see KOER 75, 77, and maybe 76 from the missed BOO and goose tests. Considering how poorly it's running, I would also expect to see KOER 12 and/or 13 show up. Plus any other codes that may show up.

Let me know if I can help explain anything. Basically, we need to repeat the tests until we get information we can understand from them.

 

[dnoot]

Mr. Shorty - thanks for the link - that one is very descriptive and easy to follow. I somehow missed it in my previous searches. I'll try again and report back.

I read that the '91 should have two digit codes, so when I saw three, I repeated the KOEO test a few times. Got the same results each time. Perhaps the computer was swapped before I bought the vehicle. I'll confirm either way.

Don

 

[dnoot]

OK - checked it out again. Let it warm up, had to keep on the throttle to keep it running. Payed close attention to the revs - tach reading is accurate (I guess I was fooled by the noise & missing type action). Once warm, it would keep running at idle, but still rough. Occasionally, it seems to "catch itself" - the revs come up and it smooths out - although this only lasts for a split second or two at a time. Seems to be running lean.

The computer must have been swapped out, since I definitely got three digit codes:
KOEO
111, repeated
{got proper pauses around the separator this time}
CM
232, repeated
KOER
111
{pressed brake (rev increased slightly, but not too noticeable)}
flash {after 30 seconds}
goose
412, repeated

So a CM code of 232 is "EI primary coil circuit failure", and
a KOER code of 412 is "Idle speed system not controlling idle properly"

Any ideas?

TIA,
Don

 

[MrShorty]

KOER 412 is usually more symptomatic than diagnostic. Basically it means that the engine is running rough, but you already knew that.
I haven't ever seen a CM 232 before, so I'm not exactly sure how to approach this one. I think you're going to want to start by checking the Ignition coil and make sure it's good. The code description suggests that the computer is seeing a fault on the primary side.

 

[dnoot]

'91 Ex barely runs, no power - FIXED!

Turned out to be the Electrical Distribution module, or EDIS. On my '91, this little black box (2.5 x 4 x 0.5 inch with 12 pin connector at right angle) is mounted right behind the passenger headlight, in front of the battery. My old one had a red label, but the one I pulled from a wrecked Aerostar (mounted on the passenger fender) has a green label (says EDIS 6).

Somehow this unit is involved in providing spark, and the engine was missing on two cylinders. The module was separating from the base, and even though the electronic board inside (do you pull old parts apart?!) was immersed in gel, something must have crapped out inside. The truck had been hit on the front passenger fender a few years back, and perhaps some damage occurred to the casing that was undetected before but showed up now.

My mechanic said he's never replaced one before, and most of the parts stores and wreckers I contacted had never heard of it. Looks like the only place to get them new is the dealer, for over $400 Cdn. I snagged one at a wrecker for $25.

Upon replacing, it immediately ran smoother, and after warmup and the computer settling down, she's back her old self.

Shorty - thanks for all the help!
Don

 

[vrytired]

Turned out to be the Electrical Distribution module, or EDIS. On my '91, this little black box (2.5 x 4 x 0.5 inch with 12 pin connector at right angle) is mounted right behind the passenger headlight, in front of the battery. My old one had a red label, but the one I pulled from a wrecked Aerostar (mounted on the passenger fender) has a green label (says EDIS 6).

Somehow this unit is involved in providing spark, and the engine was missing on two cylinders. The module was separating from the base, and even though the electronic board inside (do you pull old parts apart?!) was immersed in gel, something must have crapped out inside. The truck had been hit on the front passenger fender a few years back, and perhaps some damage occurred to the casing that was undetected before but showed up now.

My mechanic said he's never replaced one before, and most of the parts stores and wreckers I contacted had never heard of it. Looks like the only place to get them new is the dealer, for over $400 Cdn. I snagged one at a wrecker for $25.

Upon replacing, it immediately ran smoother, and after warmup and the computer settling down, she's back her old self.

Shorty - thanks for all the help!
Don

oohh interesting. never heard of one of those things dying before.