Hello Fellow Toyota Nuts,

Thought I would double check my ‘90 4Runner timing due to sluggish performance. I have set the timing successfully on this car numerous times in the last 29 years so I know the basic stuff on how to do it. What I saw was very strange and I’m a a loss to understand how to fix it.

The timing mark mark on the crank pulley moves about a quarter inch counter clockwise on every flash of the timing light. If you continuously trigger the light, the mark will travel all the way around the circle and reappear on the rise from the bottom of the engine.

I tied another light hoping that my 27 year old MSD unit was at fault. No joy.

The engine starts fine, sounds good, runs smooth and does not ping. It is a little weak however. To be fair, it has 330k miles. It is on the stock ignition system.

Clearly the ignition timing couldn't constantly advance BTDC like that and run smoothly.

Have any of you encountered this? Thanks in advance for any guidance.

Russ

 

My first guess is that you've failed the harmonic balancer. The balancer has an annular rubber ring between the part you can see (with the pulley grooves and the timing mark) and the part that fits (with a woodruff key) to the crankshaft. At just about 19 years, some of them give up so that the outside of the ring is no longer firmly connected to the inside. I suppose this could mean the outside part is rotating just a little slower than the crankshaft, which would produce the marching timing mark you see. I'd find it surprising that it would slip so uniformly, but that's all I can think of.

The check isn't difficult. Pull plug #1, and with a straw or chopstick (don't use a screwdriver; one slip and you can gouge the piston) feel for TDC. Is your timing mark spot on? If not, you'll probably need to remove the belts to see if there is any play. (You'll probably have to push pretty hard; if the belts are driving the accessories and slipping only slowly, you're not going to be able to move it easily.)

 

Thanks Scope. Will try it over the weekend. I'll also look to see if the 'march' (perfect description BTW) changes on acceleration and deceleration as a slippage might.
Hope you have a great weekend.

Russ

 

Sure enough, the mark marches much faster when the AC compressor is on or when you goose the gas, The balancer (Dorman) and all three belts (Gates) are about $167 these days.
Thanks to Scope and the whole community for keeping this board in play. -Russ

 

Consider checking RockAuto. The price for those components adds up to quite a bit less than $167.