Good Day All!


I guess I need some help. My 1992 4x4 AUTO SR5 ExCab pickup with 263,000 miles seems to run fine but, after warming up it will "huck and buck", sometimes shut off but always restart, and show code 12 and 14 when checked.

What I've done/checked/replaced so far.

new Distributor (factory one OHMed good but it was puking a little oil (new plug for distributor soldered on)), cap, rotor, plugs, (kept the OEM wires as they looked ok and i've never had any suspected issues)
new Ignitor and Coil (ran worse with the aftermarket Ignitor so i put the OEM one back on)
new Ground connectors all over engine
new ECU temp sending unit and its connector soldered on (wow this thing was shot and crumbled when I fiddled with it to test)
checked (2 wires IGF IGT) wiring for ignitor back to ECU (1 ohm or less observed to ground even when shaking and wiggling wires at various points across harness)
checked and set timing to 12 deg.

After replacing parts, truck seems to idle and drive fine BUT theres alot of knock and pinging from engine when accelerating (played with timing from 8-12 degrees same result) AND after driving for a while engine will huck and buck (CEL light flashes) and cut off sometimes, shift to neutral and truck will crank right back up.

another interesting note: when I use paper clip to set/check timing, it is almost a sure bet after a few seconds the truck will die and not restart til the paper clip is removed. ALSO, some times the timing will drop to 0 degrees when checking timing for no apparent reason.

what should I check next? and THANKS in advance.

TS

 

If you read the FSM, you're not supposed to remove the test jumper while the engine is running. Shut it down, remove the jumper, then fire it back up. If you pull the jumper while it's running, the ECU gets "confused", and can do odd things, as you noticed. With the jumper in, the timing should be set to 5° BTDC. After removal of the jumper, it should be 12°, just as a check.
Personally, when I set the timing in my 87's, I put the jumper in, set the timing, shut it down, pull the jumper, and then pull the negative lead off the battery for a minute of two, to completely reset the ECU. It seems to help the ECU get "used to" the new settings. It takes a couple decent length trips to get everything really settled down and working right, but after the ECU finishes "learning" again, it runs like a dream.

Not a really complete answer, but it's wht I've got...
Pat☺

 

****UPDATE 10/27/2021****


So, I changed the Throttle Position Sensor and now the truck drives much better. No CES light, no Hucking and Bucking while driving. Still get code 12,14 when trying to start the truck, when it is warm, so i will start checking things again now that the TPS has been removed from the list of problems. I went back with an OEM Denso TPS. On my quest to fix my truck, I have been finding out that it is hard to beat the quality and fitament of true OEM parts. To anyone reading this, If you want a cheap way to make your truck run better, CHECK, CLEAN, or CHANGE any suspect grounding points on the Battery, Body, or Engine. None of the new grounds fixed my stalling, hucking and bucking problem, BUT I could tell the truck performed better after improving the grounds. Good Luck. I'll report back when I finally get my CODE 12, 14 issue nixed.

 

Amazing the effect a ground point can have, isn't it?
It sounds silly, but keep them in good shape. It will give you much value in return.
Don't forget the ground points behind the two cabin kick panels. They are prone to water intrusion. The one on the drivers side, with 4 wires crimped onto one o-ring, is especially troublesome. The crimps get loose with age, AND the o=ring corrodes, as does the body metal. Usually has a layer of paint under it, too. Best to clean that paint off to get a quality, metal-to-metal contact.
The ground point for the head, on the firewall right behind the head, is another one to have paint, and/or corrosion, on it. The better that ground, the better spark you get from the plugs. Again, metal-to-metal is what you need.
Don't be afraid to replace the ground wires entirely. Or to add one where you think it's needed. Can't go wrong with an extra ground or two.

Good luck on figuring out those CEL codes. They may or may not tell you exactly the problem, but at worst, they give you a good starting point.

Have fun!
Pat☺

 

*****UPDATE---FIXED IT*****

Changed the ECM and truck runs fine now.

New ECM fixed several issues.

Truck starts quicker now.

Steady idle now instead of varying 200 or so RPM.

When pulling out of drive way, the first 1/8th of throttle, the truck would stumble just a little....Gone now instant throttle response when cold

No spark knock when accelerating now.

Better acceleration, faster down shifting of transmission.

Thanks to all who responded.

 

Where did you get your ECU?

 

Autozone