xzen73x

Me and a buddy are having a hell of a time getting his truck running, so i thought I'd post up here and see if anyone can offer some insight. The rig in question is a '88 Pickup 3.0 5spd

It started off with his knock sensor going. We tested for codes, and got Knock sensor, TPS, and something for an auto tranny, which we disregarded because his truck is a 5spd.

After ripping apart the motor to get to the knock sensor, only to find the previous owner replaced the pig tail with 12guage speaker wire, we replaced that, and the truck actually ran, but the idle was really bad, and was still misfiring, so we did cap/rotor/plugs/filter.

After all that, we still had misfire issues, so we went on to test codes again, and TPS still showed up. Seeing as we couldn't find parts for the '88 3.0, we did the next best thing, and grabbed a TPS off an early 90's 3.0.

Upon inspection, we realised the TPS for the '90 and '88 faced different directions and the new TPS wouldn't work with his throttle body. I had an extra throttle body sitting around so i grabbed that, and we went to work.

New throttle body installed, and we realize that the TPS connector between the years was different, and wouldn't match up, and luckily he grabbed the connector from the TPS as well, so we started splicing the new plug on.

New plug on, TPS in spec and installed, fired up and still ran like crap. I had an idea, we'd take the throttle body off my '90 3.0 and throw it on his motor to see if it was a TPS problem, and this video was created.

https://www.youtube.com/watch?v=hN-N...ature=youtu.be

After some screwing around, we started messing with the plug wires, and the idle got significantly better when you pull cylinder 1/3, slightly better when you pull 5, and wants to die if you pull 2/4/6.

Throttle response is instant, has tonnes of power when you drive it, but idles li junk, and we're running out of things to fix. Do you think there's a possibility f the newer TPS sending a bad signal to the older ECU? It still misfires while the TPS is disconnected though. any help would be greatly appreciated.

nv4runner

Have you set your base timing? How about firing order? Pulling a plug wire and having idle improve doesn't sound right and not TPS related at all. I'd double check the firing order and timing.

xzen73x

At first, we thought it was timing related as well. Pulled upper timing cover off, and passenger side cam was off by 1 tooth. Neighbor comes over and looks, cranks it over a dozen or so times, and bam, teeth line up perfectly straight. We did that again and the teeth still lined up straight.

All plug wires go to the correct cylinder, we made sure of that when we were pulling everything.

I'm not sure if it's a tps problem or not, because it still misfires even when the TPS isn't plugged in

wireguy

I have no familiarity with this engine but if you have covered all the other bases I would look very hard at cam timing and all the mechanics that control it.

Kiroshu

Verify proper engine/ignition timing.

Possible VAFM(Volume Air Flow Meter) fault..?

Intake air/vacuum leaks..?

EGR system fault..?

Cylinder compression..?

You mentioned the timing belt was off a tooth and then to turned the engine several times and it returned to normal..? Unless there was an error in reading the timing marks. Then this could be a problem.

Damaged timing belt..?

Verified all timing marks correctly line up/correct belt tension.

Teeth missing from timing belt..?

This may all be irrelevant of course.