BajaRunner

I have a misfire that happens when I am in neutral, I don't notice it when I am driving... (However it feels that the engine is struggling under load).

Jumping TE1 and E1, I set timing to 5*.

Pull the jumper out and it advances to about 12*.

I disconnect the TPS, and the timing advances way off the gauge...its probably 30*, and the engine idles smooth as silk. I open the throttle and no misfire... (The misfire increases in frequency with RPMs when its set at the "correct" timing).

When I advance timing by rotating the distributor all the way maxed, it runs better as well.

Right now for 5* base timing, the distributor is right halfway between its adjustment. The timing mark on the cam gear is at 12 o'clock @ #1 TDC.

Whats going on here guys?

Ive done:
Adjusted valves to spec.
Replaced plugs, cap, rotor
The two primary wires going to the top of the dizzy seem old and crusty... But not corroded or mangled.

Also the engine supposedly has an "oversized cam" which I am unaware if modifying the timing would be needed?

SoCal4Running

I got the same thing going on here. I have been replacing things like crazy (actually replacing neglected items) and have yet to cure it.

How old is your TPS? Has it been adjusted/check?

Vacuum hoses all in good shape/replaced?

myyota

How long has it been since the timing chain has been replaced ?. The cam gear looks like it has a lot of wear on it, but it could also be the angle of the picture ?.

longtravelyota

I had a similar problem I would set the timing by gun and it would run like crap so I set it by ear and now it runs good maybe bad gun on my part.

BajaRunner

TPS is in spec, but I feel that part of my problem is the TPS. A new one from Toyota should be here tomorrow.

Yes, vac lines are good, compression good, O2 sensor good, everything pretty much checks out.... I'm just super confused. I am just going to start replacing the common parts like O2 and TPS sensors...

My old thread (Sluggish 22re) I go over what I've already done. This is a new topic that I finally became aware of.

Don't know about the timing chain. I can't tell if its original or not. The guides look fine, and it seems pretty darn tight....A slight rattle only at 4000 RPM. I have a brand new timing chain and kit, I may try and tackle it myself this week. I need to do some reading. Any writeups for doing it w/o taking off the head would be appreciated

BajaRunner

Trying to think logically here:
1)If the misfire was caused by a sensor, or if the sensor was out of whack, wouldn't it cause a CEL?

2)Since the misfire only is heard when I'm revving the engine in neutral, and not under load, would that rule out a faulty ignition?

3)Vacuum leaks would cause a rough idle, I don't have rough idle.

4)The miss gets more frequent with RPM and TEMPERATURE. If the timing chain is indeed getting stretched, it would throw the mechanical timing off vs the iginition timing.

Thats where I am now. The PO had the head redone and bought a new timing chain kit. The mechanic who did the work said the timing chain was fine and didn't need replacement (Dumbass). I'm assuming the timing chain is indeed stretching and throwing off the timing. Even though it seemed "tight" and I dont get much of a timing chain rattle, is it possible its still going bad?

Like I said, the picture I posted above is at #1 TDC, when I adjusted the valves. The cam gear was at 12 o'clock.

If the timing chain is loose, would it cause the need to make the ignition timing more advanced to match the mechanical timing?

BajaRunner

Looks like the TPS cured the problem... For now. Bought a new one. Old one was giving some funky resistance readings via dynamic testing.