alpha1eleven

My 1991 Yota pickup 3vze (auto) was running a little rough and stalling the other morning at idle. I was in a hurry the other morning so instead of diagnosing what was wrong I simply turned up the idle via the idle screw. This did nothing. So, I then adjusted the actual throttle cable and got it to idle higher which prevented it from stalling. I went to go drive to go get new plugs and wires and noticed the tranny would not downshift automatically. I figured perhaps because of the adjustment I made to the throttle cable maybe I left some slack in the kick down cable. When I returned I let the truck cool down and began putting in new plugs and wires on the passenger side while my friend installed plugs and wires on the drivers' side. When we were done we fired up the Yota and I put the throttle cable adjustment back to normal. The truck ran much better and did not stall. However, I then noticed my friend had unplugged the TPS when doing the plugs and forgot to plug it back in. When I plugged it back in the truck immediately began running like crap again and stalled. I unplugged it and it idled fine again. I took up as much slack from the kick down cable and went to the auto parts store. It still would not downshift but I'm guessing maybe that's because the TPS was unplugged. I bought a new TPS and installed it, plugged it in and the truck immediately ran like crap again and then stalled. What's next? I've tried searching but am not having any luck. Any suggestions will be much appreciated.

Gevo

Well, I'm interested to see what the fix is. I would check the TPS connector, make sure it's clean. It could be somehow slightly shorting two or more of the connector tips in the connector and that could be adding to much resistance to the signal going to the computer which in turn screws up your timing.

I found a faulty TPS connectors to be the cause of a total spark blackout.

alpha1eleven

Thanks, I haven't checked the plug yet. I'll do that next and let you know if I have any success.

alpha1eleven

No luck. I checked the plug and it's clean. Looks brand new. Any other ideas anyone?

alpha1eleven

I was able to trace two of the wires to the air box. I don't know where the other two go....

vasinvictor

iTrader: (3)

There's a proper TPS adjustment procedure. It's outlined in the FSM, and also here http://4crawler.com/4x4/CheapTricks/TPS/index.shtml

I'l tell you it's much easier to adjust with the throttle body removed from the truck. Takes about 20 minutes to remove it. You can't just slap a new TPS on there without adjusting it or you'll have a horde of running and shiftiing problems.

alpha1eleven

Solved it. - there was a hole in my airbox. Couldn't fix it with duct tape so I used more duct tape. It's all better now!

vasinvictor

iTrader: (3)

But a hole in the air box is before the AFM so it wouldn't make any difference if you had a hole. In fact a common mod is to drill a bunch of holes in the bottom of your air box. What am I missing?

alpha1eleven

I should have been more specific. The hole was actually located on the black plastic box between the two rubber air intake hoses that come from the air box and the throttle body. The one that acts as a 90 degree coupling. It was caused by the airbox not being bolted down and it was rubbing on either the steering column or exaust manifold. So after the AFM.

vasinvictor

iTrader: (3)

Ah, yes that will absolutely do it. Nice work, glad you got it sorted out.