Yes the sensor was completely disconnected when I tested it. I checked the continuity several times to make sure it wasn't my error or my meter's error. All the others were in spec except that one.

 

Update:

So I went out to start the truck and it started and revved fine but the idle wouldn't drop below 1500 and the timing was way advanced. Keep in mind that the timing was set correctly before, and now it has randomly advanced itself. I let it warm all the way up. Then I decided to hop in and run down the road to see if anything changed. When I got in and slammed the door, the idle suddenly dropped down to normal. So I got out and checked the timing and it also was within spec. And now once again it won't rev above 1500, but idles normally. It definitely seemed related to my door slamming. This one is wearing me out....

 

Any ideas??

 

I'd like to come at this from another angle. Which electronic components could make the motor randomly jump up to 30+ degrees of timing at idle sometimes, and run normal timing at other times? I just don't want to overlook anything.

 

Chris- have you checked TPS yet as suggested?

It can only be one of two things that would advance timing like that.. TPS or knock sensor.

My guess is it's TPS. Check the link I posted on page 1 for directions how to test it / set it properly. It's a pain in the butt, but ya gotta make sure TPS is right or the engine will guaranteed run like crud! You need a set of feeler gauges to do it right.

EDIT: yeah I see you've already checked it. I still think it's not adjusted right. It's more than testing the voltage at the ecu. The critical measurement is the one where it changes to idle, I forget the pins but its the one that's around .8mm off. That needs to be exact right where the resistance goes to infinite

 

Yeah, I keep coming back to that as well. I'm going to pull the throttle body off again tomorrow and redo it. It Just seems to change from correct timing to way advanced too easily. Seems like if it was the tps, the timing would just stay put in the wrong spot. However, since I have no code for the knock sensor and the sensor pigtail is brand new, I don't suppose there is much more to check. Maybe the new tps that I bought was one of the rare "bad out of the box" anomalies....

 

Hi Chris

Toyota OEM TPS, or aftermarket? I once tried to replace my TPS with one from Autozone- didn't work at all. Totally out of spec. Amazing

Gotta go with the OEM for TPS.

Also to answer your question earlier, I think it does make sense for it to be the TPS = I had a much similar situation when mine was out of adjustment...

During open loop warming up (cold) it ran okay. Then it would intermittently decide to work, and it would get to the point where I had to keep my foot on the throttle in order to keep it from dying (engine not realizing it needs to be idling, lets the engine die). I also seem to remember someone mentioning the engine will go into trouble mode (open loop) again if it senses there is a problem. This could be the oscillating thing you are talking about where it is sometimes fine and sometimes messed. I really think it's probably the TPS!

Also, I got no codes when my TPS was out of adjustment- just a bunch of bullcrap idle and surging around 1500rpm. It was like the motor would hit a wall when I tried to rev it up to 2000.. Unless I floored it and gave it enough momentum to reach past and then it was fine up until redline.

Seems like exactly the same thing to me from the way you're describing it!

 

Alrighty. I greatly appreciate all the finger-pointing towards the tps! I pulled the throttle body off and installed a new tps with an ohmmeter and feeler gauges. I opened up the iac valve and cleaned it out. I also noticed that the previous owner, in an apparent attempt to make the truck run correctly, backed out the idle bypass screw. So I screwed it back in to where it should be approximately. After doing all that, the problem is gone. Not sure if it was a combination or what, but it's better. Thanks to everyone!!

I do have an issue that I need some help in understanding... In order to get the timing to about 10-12 degrees advanced I have to rotate the distributor as far counter-clockwise as it will go with the bolt in. If I restab the distributor a tooth over, the problem is reversed and I can't possibly advance it enough. So I m certain it is in correctly. What would make it to where I had to turn the distributor so far? Is there another sensor that could cause this? Also, I seem to have low power at highway speed and a misfire around 1,500-2,000 rpm while accelerating, if that helps any. It feels kinda like I'm not running enough timing, although the timing light says I am. Timing too far retarded would also explain the position of the distributor. Please, any ideas? Next thing I'm thinking is just advance the timing and ignore the mark, although I hate to do that....

 

The same problem returned! Randomly this morning, after 3 months and a few thousand miles of driving, I had made it 6 miles from home and the truck once again began reving only to about 1300-1400 rpm and the cutting out. Any suggestions? Possibly an intermittent ect sensor issue? This is getting old.

 

Above the kick panel next to your left foot there are two grounding points. Cut the terminals off, crimp new ones on, re attach and re-test.

 

I still have the same problem, but I have a new clue. I've noticed a faint click noise from the engine bay when me truck switches to "pain in the rear" mode. So I tracked it to my charcoal canister vsv. I stood there and for a while and every time my truck started running like crud and not revving, the vsv clicked open to allow engine vacuum to draw the fuel vapor into the intake. Truck switched back to running well and the vsv closed. I'm sure the canister vsv isn't causing the problem, because it functions perfectly, and the problem is sill there even if I unplug it. So whatever is causing my motor to go into "limp mode", or whatever it is doing, is also triggering the vsv. My big question is, what conditions trigger the vsv?

 

So you replaced those ground connectors?

 

No I did not. I probably should have, but I inspected them closely and could not see any issue. I swear if that turns out to be it....

 

Ok, so I cut off the grounds and reattached new connectors and nothing changed. I wish that had been it. You can audibly hear the change in the way the motor idles because the timing changes. So even while it was sitting there idling today, you could here it going back and forth every few minutes between running right and running wrong. Any suggestions?

 

Dude same problem ive been having with my 3vze on my 93 pickup. I bought it with this condition. Timing gets weird when it breaks up. I can coax it to rev out by holding the air flow meter door wide open. Did you ever resolve your issue?

 

I realize this reply is a year and a half late, but no, I never solved the problem. So if anyone has any more suggestions I’d be happy to hear. I still have the project truck.