2.3L ('83-'97) 1990 2.3l dual plug, tach dead, off idle miss

[corerftech]

Good morning folks.
I acquired a 1990 dual plug 2.3 ranger (manual) and it was a Mississippi car——- backwoods and bubba hurt it (not many teeth left from the METH)

engine is replacement and mechanically excellent.
I have resolved the gauge issues (oil pressure, fuel, etc) as bubba hurt the wiring and the Inst Cluster fuel slosh filter failed (100uf cap).
I have sorted a number of shorts under hood. Lots of solder and shrink tube and re-loom.

Using an OBD-1, a DVM and a couple of high impedance probes, I have resolved all but two things.
A tach issue (tried a replacement tach, no avail) and an off idle miss.

codes that have appeared
18 (spout)
48 (Coil3 shorted)
56 (MAF output too high) just once

in testing the ICM I found a fault for intake coil pack. CKP/CID all test perfect. All lines in and out of ICM test perfect (now). Coil pack two driver didn’t look right under run test with test probe. Looked like a steady and not flashing light. I assume the ICM has a coil trigger fault for intake coil pack….. but it should be able to live with that.

No problem, unplug and who cares.
MAF output was after all repairs Completed and a first test run with MAF pipes instilled and wired (MAF wires had essentially bonded by rubbing on a metal part and all shorting), no air filter installed, code 56 (IIRC). Saw it once and only before installing the air cleaner. So ignore that one. MAF is visibly in good condition, haven’t tested the device itself yet. But in all troubleshooting the 56 didn’t pop up until I ran with MAF installed but no air filter (wide open). I’m guessing that flow was very high and out of range due to missing air filter. Added filter, code now gone.

I still have an off idle miss and the tach is dead. At crank tach bobbles once or twice and then is motionless. I have yet to put a dwell tach on blk/yel to see if an external tach works but I suspect it won’t.

I have ordered against my desires, a Standard LX230 IDM, arriving Wednesday.

My concern:

SPOUT comes from ECU to tell ICM to fire coils with timing changes. IDM out tells ECU the basic waveform of the coil packs so it knows what’s going on (and drives tach).

Dead tach and an off idle miss (bad stumble).

ICM, if bad, wouldn’t drive tach at IDM out, wouldn’t send ECU pulses for correction.
ECU if bad, wouldn’t send SPOUT even if IDM out out is kosher.

Given the Ignition module isn’t driving the tach…….
What say ye on ECU vs ICM failure?

Chicken or Egg?????

Again ignoring ALL other things (car starts and idles well, no CEL, doesn’t smell rich——- SPOUT not shorted as far as I can discern (it may have been before wiring repairs performed, many rubbed through wires needed addressing).

Since wiring repairs made the truck run really well (relative to when I acquired it!!!) like night and day I am working from standpoint that ALL wiring faults are remedied——-

mind you, 4 of 8 plugs were only hand tight, literally, and popping loose and breaking ground with every ignition cycle.

MS meth heads in the back woods can be rough on what was a good vehicle.



thanks in advance for the insight.

 

[scotts90ranger]

The tach is driven off of the intake side coil pack, so if that's not working the tach won't work. My turbo engine is just running one coil pack and I spliced the two coil outputs together to the same coil pack which got the tach working.

I know mine has a SPOUT connector, if yours is missing the SPOUT jumper that could be the issue with that part. I don't remember which bolts are on the ignition module but it's only using 3 of the 4 bolt holes, don't use the 4th as it grounds something out that shouldn't be...