I'm working on a '90 4Runner that is more underpowered than the average 3VZE (on a very slight incline, couldn't get past 60mph). Tried to check the ignition timing and am getting odd results when jumpering the diagnostic terminals. Check Engine and O/D light flash appropriately, but engine does not slow down and the ignition timing actually advances while the terminals are connected. Disconnected, it's showing ~13 BTDC, but jumpered it pushes to 15 degrees. Whether connected or not, timing advances when the engine is revved. Checking the TPS, the idle position switch is closed when the throttle is closed, opens as soon as the throttle is bumped open. Any ideas on what else to check?

Will also be changing the fuel filter and inspecting the plugs in the next few days. A compression check might be in order, but want to hit the basics first.

 

well, if you can get the proper reading on the TPS IDL / E2 contacts, and set the idle speed and timing to spec, all should be good, and then you're left troubleshooting other issues.

 

Right, but I can't set the timing because something is keeping it from going into that mode. The typical TPS issue wasn't the problem, so I'm trying to find out where to test next.

 

Does anybody have a list of what will keep the system from letting you set base timing, other than a misadjusted TPS? That would be very helpful. I dug around in the shop manual and searched here, but may have missed it.

 

Bad distributor?

YOu are jumping T1 & TE1, correct?

 

Yes, that's correct. Jumping them flashes the diagnostic lights, but seems to advance the timing a couple of degrees and there is no noticeable affect on engine speed.

 

What would you suggest as a good way to test the distributor?

 

Pull it out, check for excessive play or obvious wear, and check the internal bits for any degradation or corrosion. The distributor section of the FSM is HERE:

http://personal.utulsa.edu/~nathan-b...13distribu.pdf

 

Any news?

 

Not yet - we're running back and forth between him helping me on a kitchen remodel and me helping him out on the truck. I'm gone this weekend so it may be Monday before we get to troubleshoot again. Sorry - wish I could give you some feedback on your advice sooner than that. I certainly appreciate the help.