NotSoNew92

New TPS is back in and it fired right up and is staying on. I'm making improvements again. Idle is now at a hair over 1000. Letting warm up, them checking timing and trying to adjust idle speed again.

NotSoNew92

My idle is now bouncing around from 800 to 1000. I've changed nothing except let it get up to temp. This misfire just got more interesting too... When the revs drop to 800, cyl 3 gets spark. When they go to 1000, cyl 6 gets spark. Any ideas on what that might be? Maybe pointing back to the distributor again?

NotSoNew92

Just did a dry, cold compression test and got 120-130 PSI on every cylinder except 2, which was 100. That cylinder hasn't given me any trouble yet so I'm going to keep going with this, but I'll keep an eye on it.

NotSoNew92

Just finished putting on a new distributor complete with cap and rotor, new NGK plug wires, and new NGK copper core plugs. Fired right up, then started missing again immediately. I started off getting no spark on 6, and then it traveled back to 3 again and 6 started sparking. I'm at a complete loss here.

Any new suggestions are welcome.

NotSoNew92

Oh and FWIW, the old plugs were all pretty black and smelled like gas. At least I know my injectors are all firing.

Also, I tried adjusting idle with the adjustment screw on the TB and saw no change in idle. Timing is still at 30, despite following the FSM to install the distributor.

NotSoNew92

Cleaned the ignitor and coil bracket and saw no change. Changed back to my old coil and saw no change.

Why is it that the engine runs great for the first 30 seconds, sparking on all cylinders, then drops idle and stops sparking on 6? What is going on with this thing???

NotSoNew92

Yesterday I bought and installed a second inline spark tester. With inline testers on both 3 and 6, I verified that I am in fact NOT getting spark at all cylinders when it starts up. Either 3 or 6 is consistently missing spark. The odd thing is, I can get it to bounce the spark miss from one cylinder to the other by revving the engine up.

Is this ringing any bells for anyone? Is anyone still following this? Any other suggestions?

NotSoNew92

I'm now wondering if my mechanical timing is off. I picked up a new timing belt with the timing marks on it so there's no mistaking how it installs. I looked around for info on the number of belt teeth between the tick marks on the cams and crank, and was unable to find anything. For those looking for the same info, here it is:

Total Belt Teeth: 193
Teeth Between Crank and L Cam: 77
Teeth Between L Cam and R Cam: 46
Teeth Between R Cam and Crank: 70

edit: the Left Cam is the driver's side. Apparently it's considered the Left Cam when you're sitting in the driver's seat, not standing in front of the engine and working on it. Go figure.

I've counted these numbers a few times, just to be sure. I'll report back shortly about how my current belt is aligned with this new info, and whether or not it makes any difference with my ignition timing and misfire. Fingers crossed.

stefanc

Keep us posted.

Eager to hear what the issue is.

NotSoNew92

Fired it up a moment ago and I still have the bouncing misfire going from 3 to 6 and back again. I have two inline spark testers, one of each cylinder, and I can watch it bounce from one to the other when revving it up.

My initial timing was again about 30°BTDC too. I killed it, rotated the distributor a tooth, and I've finally gotten it to 10°! Still misfiring though, and it runs terribly at 10°. I'm going to play with the idle speed again to see if that makes a difference at all.

Still not seeing any change when jumpering Te1 and E1. Still not sure what that means either.

NotSoNew92

Got the idle to about 800 RPM, timing was at 8°, still had misfire one on cylinder. Revving it up gets both to fire. I have no idea what to do with this and I'm done investing time and parts on it.

Sorry to end this thread like this, but unless anyone has any great new suggestions, this truck is either being sold as is or I'm parting it out.