Non-Turbo 2WD.

Purchased a month ago with 98K on it, new body. There was no engine issue at the time.

Engine started knocking/misfiring/stalling at idle. When gas is applied it wont stall out, but there seems to still be some misfiring. It is never rhythmic. First I changed the plugs, no difference. Pulling the plug wires while the engine was running seemed to effect the engine no matter what plug I pulled (started choking up even more), though the middle two plugs when pulled seemed to make less of a difference than the outer two.

Tested the codes and got code 5 (o2) and code 11. I unplugged the battery for a little while and reconnected. Only code 11 showed up.

I took off the TPS connector and tested each connection with a multimeter. IDL and E2 Always read 'open resistance', regardless of throttle position (should give me 2.3k Ohms at .5mm and open at .8mm or so).

I removed the TPS (Holy pain in ass, stripped screw!). The brown rotating piece inside seems mechanically sound (was all the way close, when turned fully and I let go, it quickly snaps all the way shut).

I have not yet replaced the TPS and restarted the truck to see if just fiddling with the pieces did anything, as it likely did not.


What do you guys think my plan of attack from this point of would be? Should I replace the TPS? or from what I described do you think the TPS is fine and it could be the ECU, wiring, etc?

Thanks everyone!

 

Update:
I purchased a new TPS; TPS436 by Wells ('Exact fit for you 86 pickup 22re.

Some things I noticed:
The old TPS, while removed, would read 22ohms with no 'throttle' on E2+IDL. Turning the wheel would have no effect until a certain spot was hit which would make it jump erratically between 200-350 ohms, though I saw it jump to about 1,035 for a split second. This 'sweetspot' was literally micrometers. The micro tremors in my hand would make it go back down to ~22 ohms, or to infinite. This seemed way off.

The new TPS, attached, would gives me ~200 ohms with 'closed throttle' for IDL+E2, and 1.2K ohms for E2+VTA. When opening throttle, IDL+E2 Jumps around between 120 and 300, never getting near that 2.3K that is the test limit, though the guides say '

 

Setting the TPS sounds easy as it is just a Ohm meter and some feeler gauges. Should be easy enough but it kicks my butt. I have done plenty of resistance or feeler gauge settings, but I have my TPS set for me by the dealer. I just take the Throttle Body and TPS to them and they charge me half an hours labor.

The 85-87 injector connectors are a poor design. Make sure they are connected well. I have had them to cause a miss on me in the past.

 

UPDATE:
- Did a timing check. It was hard to see the faded mark even after a attempt to file it a bit. It seems to reside slightly to the right of the 5, though the mark isn't stationary, its a little jumpy to the left and right. I assume this is normal?

-While checking the timing, I notice there are sparks around the engine, drivers side. Particularly, there are 3 spots or so that seem to be bridging a very low voltage spark between insulated wires. Didn't notice this until it was dark out. By low voltage I mean about what you get from rubbing wool socks on the carpet (thats how it felt at least)
Is this normal?


Thanks Terry, I will look into that.

 

UPDATE:

I Just changed the spark plug wires with nice new ones; sparking is gone, miss fire and engine shake is gone but now theres a new issue.

The engine runs VERY rich, and blows soot out the tail pipe. Do you think its due to TPS misplacement, or do I need to drive it around for a few minutes to get the ECU (which has been reset) to calibrate to the new TPS?

I don't want to test the second theory until I am reassured it shouldn't cause any damage to do so.

Timing seems to be between 3 and 5.


EDIT::::::::::::::::::

Nvm, went right back to same issue almost immediately; missing at idle. Guaranteed stall if I go from under load and gas to pressing in clutch and releasing gas. Still shaking like a big ol booty.