1990 4 runner, 95ish 3.0 auto trans
last summer vehicle got very hot and quit. found timing belt had jumped several teeth. Re-aligned timing marks, ran fine. put new belt, tensioner, idler. If i set timing at 10 degrees with the jumper in, had no power. moved timing to 20 degrees +- (no marks that far out). ran ok. 8 months later, truck returns with low power, timing light shows timing at 10 degrees again (?) Move it back to 20 and away they go.
2 questions.
why would it not run at 10 degrees but fine at 20. Crank pully times out perfect with timing belt marks when it was apart. Don't think its a spun crank pully.
what might cause the timing to move at will. Distributor is tight, new cap, rotor, wires, plugs. perhaps gear that drives distributor shaft off left cam?
I don't know if the ECM was changed with the motor, i have a feeling it was not. don't know if it would have to be. I'm kinda stumped here.
Thanks for your time folks.

 

Are you sure it's going into timing mode with the jumper in?
If the check engine light is not flashing then it's not in timing mode.

 

Yes, the CEL is flashing when the jumper is installed.

 

Only thing I can think of that would cause timing to adjust on the fly, short of jumping gears (and the dist gear is spiral so shouldn't happen easily) is just not tightening it down enough after adjustment.

Did you pull the dist during the timing belt change and reinstall it one tooth off? It's easy to do.

If you have too much fuel in the mix from pressure being off you'll run better with advance, but if it ran ok with the old belt right before the change that would be quite a coincidence.

 

My money's on the crank pulley(like it's seperated), and/or the belt skipped teeth again(can't imagine how). It should run "fine" at 10°, even better at 20°, regardless. And jumping the check connectors would make very little, if any, difference at all. Maybe a couple degrees, if that.

 

Month or so later. 4runner came back with identical issue. Somehow timing retarded back to 10 degrees and runs like doodoo. Put in jumper, advanced distributor to the stop. Locked it down and it's running ok again. With the new timing belt, tensioner, idler pully etc, and the fact that it clears up with advance I'm thinking cam timing is NOT changing. Ignition IS changing but each time is by 10 deg (+-) perhaps cam to distributor gears are jumping. I'm sure it will come back soon and a simple advance won't fix it this time. Is there a short shaft between the dist and cam gear? Seems I don't recall the dist having a gear on the end, but I didn't pull it to change the belt. Months ago too and I've worked on too many in between and none were Toyota.

 

The distributor does have a gear that goes directly to the cam. I am having similar problems except my camshaft gears are creeping in advanve of the crank pulley. New belt and new engine but it keeps advancing as i drive it. If anyone has an answer id love to know it. This makes 3 times resetting the timing in about 4000 miles. If it were slipping on the crank the camshaft pulleys would be behind the crank instead of in front.

 

I am in reporting a similar issue. Last time I set my tim8ng at 12 deg, ran well for a long time (maybe 5k miles??) And then started becoming slightly difficult to start. I just thought its the 3.0 being the 3.0 as I checked vac leaks and blah blah. So finally i thought let me check timing, and behold, way advanced. Probably 20 or more Deg, hard to tell. But the bt hding the distr was very tight, no way it slipped. Yes, i jumped ECU.

So, i cant understand why the base ignition timing would change. And, apparently noo e really knows?

 

Make sure neither the gear that mates with the cam or the tone disc the rotor mounts to are slipping on the shaft. Pull your cap, grab the rotor and try twisting it. If it turns, that's your issue.

 

Thats not a bad idea, I will check to make sure the rotor does not have any unwarranted play or slippage.

Thanks.

 

Also, if possible, do this at operating temperature.

 

I found my issue. After I adjusted the timing back down to 12 deg, the car was sluggish, exactly what you would expect from severely retarded tim8ng. So, i put my thinking cap on and thought my tps may be the issue. Turns out, the tps was not going into idle circuit, it was out of adjustment, not the distributor/timing. Adjusted it, advanced timing back to 12 deg, good as new!

Now why the TPs went out of adjustment....... no idea

 

What is the TPS?

 

Didn't you ever see Office Space. We all need to file our TPS reports. But on a serious note. It is your throttle position sensor. It mounts on the throttle body and has a plug that hook up to the front of it. I can't find an exact pic of the location at the moment. But it is about here secured to the side of the throttle body

Edit:
I'm an idiot. I just saw its a 3.0 not 22re. Do disregard picture location. Haha. Need more coffee

 

http://personal.utulsa.edu/~nathan-b...93throttle.pdf

This is for the 3VZE. The 22re has an "almost" identical part, adjusted the same way.

Quick tip: Lots of folks agonize over "setting" the TPS. On the 3VZE, the connector is turned in a direction that makes it pretty difficult to hook up the ohmmeter leads needed. So before you tackle that job, check your door pillar: if you have the A340H automatic transmission, the computer will read out everything you need to know at the diagnostic connector!

 

Heck, at this point I just keep the timing light connected and rotate the TPS one way, then the other, and as soon as the IDL circuit is closed you can see the timing change dramatically and you pretty much have the point at which the IDL circuit kicks in. Yes, I know that I will never get the exact distance for the IDL circuit range, but I'm pretty sure it's not the end of the world