1995 4runner automatic 3VZE -Owned for 20 years 270K miles. Done the timing belt 3-4 times, HG & top end 50K miles ago. Runs great...Decided to chase down a very mild (warm) rough idle issue. new plugs, wires cap/roter ECT sensor. No improvement.

With Daignostic jumpr in place , warmed up 875 rpm...timing light and found that timing is retarded by at least 20 deg. (mark is toward driver side way off scale) Tried rotating distributer to end of adjustment and was only able to adv it a small amount but still off the scale on the retarded side.

Turned off vehicle and set the crank shaft pulley to TDC, pulled off the TB covers and confirmed all marks on place. Pulled off cap distributer cap and rotor is pointing to a bit before cyl #1.

Stumped! Decide to pull out the distrbuter....mark on gear and casing is correct.

So...since its so far retarded, decide to re-stab distributer with gear a bit more counter clockwise (further rotated before #1 cyl)

Bingo - rough start but timing is dead on at 10deg adv. ..But the motor can hardly run! rotated distrib left and right..still can hardly idle.

So, pulled distributer again and set gear back to where it was and motor runs strong...accept for the mild rough warm idle.

So - Here is my question. What would cause timing to be so far retarded when my marks are all dead on.

Thanks for any thoughts.

 

Possible that the ring on the harmonic balancer that carries the timing mark has slipped on its rubber mounting and reads incorrectly.

If this is the case, no fix but a new balancer.

 

Thx..Never thought of that..... wonder how I cold check. Is that common? I was thinking perhaps something went wrong with the distributer.

 

Verify tdc, valves closed, piston mid point of tdc, remark crank pulley..

 

Yes, the balancers are known to seperate from time to time.

You'll have to consult the FSM but if the 3-vz is like the 22r, the crankshaft keyway is at 12 o'clock when #1 cyl is at TDC. This should correspond with the balancer mark at 0 degrees.

The crank bolt for the balancer might have to be removed in order to see the keyway, IDK. This would be a way to check for movement.

 

Yes, totally agree that checking the timing mark on crankshaft is the only way to confirm. Man,...I was hoping to not have to pull it apart that far. I speculate that when I did the HG job in 2011, I may have incorrectly set the crankshaft timing to the key slot (strait upand down) and not the dimple on the crankshaft sprocket. If I did, it would correspond to being about 1-2 tooth off in the retarded direction. What I cant understand is how I could drive the truck 50,000 miles like this over 6 years without any problems? (or maybe it jumped a tooth?)

Does anyone know if the 3VZE will run with the crankshaft one-tooth off? Here is a pic from another yotatech member which shows that if I incorrectly set to the crankshaft Key( and not the dimple on the gear) then when I installed the balancer.... timing would show retarded.

 

Don't go off the deep end now Sperry. If your truck has run well for 50,000 miles, you, no doubt, have the timing belt set up correctly.

I'd get back to finding out whether the harmonic balancer has slipped its rubber. I think it has.

 

Thanks Millball..great advice. I read a post you made in another thread where you mentioned relationship between the TPS and the timing. Is it possible that my TPS is poor or failing an that is what is causing poor warm idle and throwing off the timing? (However, I thought that once the diagnosic jumper was installed it shouldnt matter and timing is true)

 

Yes, if the TPS is not telling the ECU that the throttle is closed and/or the idle speed id higher than spec, the timing will not go to base, even with the jumper in

It is also true that engine will not go into closed loop control if the ECU does not get the correct signal that the engine has warmed to operating temperature.

 

Thanks Millball - good info. I will check out my TPS. Besides ohming it out via FSM, is there a quick test like run unplugged to witness an instantaneous change?

 

Don't bother "ohming out" the TPS. You have the A340H transmission; it will check the tps for you.
https://www.yotatech.com/forums/f116...icator-303218/

 

Thank you scope103, thats pretty clever. So using multimeter and diagnostic port....
red probe: B+,
black probe E1
...what value(s) should I see for a well working TPS when 3VZE is warm an operating properly.
Also, I assume that TE1 and E1 are left un-jumpered.

 

Measure E1 (ground) to Tt. (B+ is just 12v with key-on). http://web.archive.org/web/201408160...34electron.pdf
No jumper.

 

Excellent, thanks. Will try tonight.

 

Yes, The only TPS function critical to setting base timing is that the ECU sees a 'throttle closed' signal from the TPS.

 

Thanks Millball, good info. Also will see if I can somehow determine if balancer mark has slipped as you originally suggested...although it would be a huge coincidence since in the static position with balancer mark aligned with the '0' timing mark at TDC the other two cam marks line up.

 

Yes, unlikely to be a HB failure. Unless it slipped before the last timing belt job ...

You don't have to remove the HB to check (that way you could look at the mark on the crank sprocket; the gold standard, but a lot of work to get there.) You could set it to TDC, remove the #1 plug, and drop a straw or chopstick in to feel for TDC as you rock the crank. (Don't use a screwdriver; if your wrench on the crank bolt slips, you could scar the piston, plug hole, ...)

 

Tested out TPS as per scope103 - worked well and saw clear voltage step from 0 to 7.8, so it seems to be working fine. Decided rather then waste time pondering......just dug in and pulled apart. All marks were lined up perfect. Harmonic balancer was fine as per millbank suggestion. So, not sure what to think as to why timing is so retarded.

 

You've been pretty thorough. At this point there aren't many suspects. Something is wrong with your timing light, or maybe the distributor pick up. Try another gun, after that it might benefit from an oscilloscope..
?

 

before u go on, borrow a different timing light.
I hear, on these forums actualy, quite a bit of talk about some more expensive timing lights being completely crap.
Just try another one before continuing. rule it out.