Here we go again. 1985 22re engine rebuilt 3k miles ago, was running great when the head dropped a valve seat and it stuck open. Had a spare head, newly rebuilt so I replaced the head. Put it all back together and now I cannot get it to time. I know it is on the right dist. Tooth, reset the valve clearances. It will run when you press accelerator but let off and it will idle down slowly until it dies. Adjusted idle set screw on TB until it is almost falling out and it will barely idle then. It will smooth then lope then up to smooth then lope. Can't set time because mark is jumping. Jump the pins to set time and nothing changes. I will take anything at this point. I have built several of these engines and had no problems but this one truck gives me fits.

 

i think that there needs to be a slight gap in the throttle plate, there is a spec for it, if it's fully shut the engine can't idle... is the tb really gummed up there, did you swap tb, etc.

 

Try this link
https://www.yotatech.com/forums/f116/trying-set-timing-jumper-te1-e1-doesnt-change-idle-233689/

seems like a good good place to start

 

No I haven't cleaned the TB plate but I will do that next. May be something to the tps as well, when I disconnect the tps nothing changes at all.

 

if the tps was bad i think that it would be throwing a code, so check for that.

if nothing on the tb was changed from how it was before the head replacement, it could be something other than the tb.

 

Sounds like cam is retarded to me. Particularly after swapping the head. Where'd you put the crank before you pulled the head?

 

Ok, set tps, new plug wires when I changed the head, changed computer, changed distributor. Will set the timing and will seem fine, let it warm up and still ok, drive a mile and then park and won't idle again, just misses and shakes. Reset the timing and start all over again. Will not hold the timing. Any ideas on next thing to try? Again it was running fine until I had to change the head last summer. Also it is a 1988 efi not an 85.

 

Broken wire in the harness? I had a few broken wires in mine after my engine rebuild. That harness gets pretty beat up when you route it through the plenum. Have you tried running it with 1 plug wire disconnected after it starts acting up? If you find one that you can unplug and it doesn't make any difference then it would point to something in the cylinder circuit.

 

By the way you said it would idle down slowly and then die makes me think you may have a problem with your Dash Pot. I would suggest getting it to hold a steady idle before trying to get a Timing Light on it. This is what I am suspecting.

 

The problem when I try that is even when it won't idle I can speed up the engine and it is smooth again, let off and it won't idle again. And even if I tried to put a timing light on it when you put in the jumper it doesn't idle down. Yes I need to fix the idle before I put the timing light on it, but that is where I am lost on why it won't stay in time. The only two adjustments I can make that change anything is distributor and idle control screw on throttle body. I thought maybe a plug wire but if that were the case it would miss under acceleration. With just a little gas it is smooth as a sewing machine even when it won't idle. I thought bad head but if that were the case it would be rough at higher rpm too.......right? Thanks for the help guys I am considering five gallons of gas and a match right now.

 

Remove the dashpot, it unbolts from the throttle body, you can deal with that later right now it's only possibility complicating matters.

Put match marks on the crankshaft pulley outer edge, the inner section and the bolt, this will be used to confirm its not shifting around.

Place more match marks on the idle bypass screw and the throttle body.

Open up the right kick panel and measure the voltage of VCC, Vta, and IDL signals with the throttle open and closed. The key should be on but engine not started for this. VCC is always 5volts, open Vta is near 5 and idle is near battery voltage, closed Vta is below 1v and Idle near zero. Now go shake the engine harness from the firewall to the intake clip it mounts to, and then upwards to the TPS, watching the volt meter it should not change not even a little wobble. Anything not as above indicates a bad wire, a bad wire connection, misadjusted TPS, or low battery voltage (battery voltage needs to be at least ten volts as meaaaued at the ECU).

Now warm up the engine and jumper the test line directly at the computer, this removes questionable wiring, and set your timing then readjust the idle if needed.

Attached is a crappy reference image for the pins..

 

Now test drive it, start the engine stop the engine and repeat, checking all your match marks still line up as expected..

 

Thanks I will do this, have one or two questions to get it right on my head. So I am not unplugging the computer I am checking these by leaving all harnesses plugged in and just skinning a little on the wire? When I check the voltages on VCC, Vta, and IDL, what am I checking these against? And when I jumper E2 - T at the computer again it is by skinning the wire with it plugged in. Sorry I am just not an expert at this and obviously need a little help.

 

Unplugged and against ground? Sorry I can be a little slow to catch on.

 

yes you'll need the computer plugged in and unmounted from the chassis.

no wire skinning, just insert the meter probes into the back side of the wiring connections..

Voltage reference is to ground. In the images below I have the black probe inserted into E1 to give me more hand room. you can use E1, E2, or clip to the body. E2 is ideal it's the one the computer will reference against.

For your SST(paper clip) to trigger test port, use a big fat paper clip or small section of ~17g wire inserted I to the back side of the ECU plug. Like pictured below.

Here are some reference photos. Thanks for asking for clarification before diving in, sorry I was not extra specific I don't usually verify what section I'm answering questions in. I'll try to do better.

This is Vcc
This is Vta with the pedal to the floor, notice my TPS is worn out and needs replaced since it's under four volts
Vta, again with throttle released. Note the voltage is quite high but under one volt, acceptable but not ideal.

 

Got it now. Thanks. I built two of these trucks from the frame up at the same time and one runs perfect and this one is the opposite, so I feel like an idiot asking questions I should already know. So thanks for the help and sorry for you having to dumb it down for me. Being an engineer it kills me to ask for help solving a problem. So again I do appreciate your knowledge and help.

 

Electrical sucks sometimes and CO has some very helpful advise. He and a few others have probably kept me from selling a rig or 2 throughout the last few years.