timing adjustment
 

I've got a manual 94 pickup and noticed it starting to idle hard when coming to a stop after taking it out of gear. I wasn't sure exactly why but figured I wasn't driving it enough and opening up the throttle on freeways or something. Then when smog certification came up, the truck passed emissions but failed the mechanical part because the timing was way out at 22 deg rather than recommended 5 deg from top dead center. Then I finally recalled swapping in a new distributor cap just because I had a new one lying around and realized this is what threw the timing off. So I bought another timing light (after donating the one I bought while in school) and figured this would be an easy adjustment until I saw the distributor glued to it's mount where it is meant to slide after loosening the 12mm bolt.

I was talking to the guy at O-Reily thinking I may be able to find a distro cap that matched better so that I wouldn't need to make the adjustment after all, but his first response was to get rid of the glue and how we couldn't think of the need for any sort of gasket in this area. However, being the truck's second owner I wonder why this timing adjustment may have been glued in place by some kind of need before my time. Maybe it was just to ensure the timing would never change. Anyhow I wonder how easy it would be to restore the moving parts. I have also been driving the truck for a couple thousand miles in its current state and wonder how much damage I may have done to the engine due to incomplete combustion or the like.


https://cimg2.ibsrv.net/gimg/www.yot...9bb8995434.jpg

https://cimg3.ibsrv.net/gimg/www.yot...ba12824cd0.jpg

It was probably leaking oil and rather than pull the dizzy and replace the O-ring they siliconed the distributor base where it meets the block...
Pull it, clean it, REPLACE the O- ring and time it....

I've never had to change timing because of changing a rotor bug and cap? Maybe i'm missing something...I learn something new everyday, but you'll have to prove to me that changing the rotor cap changes timing...
there's a reason the cap will only fit in a certain position on the distributor and is a fixed position...
I'd think changing blinker fluid would have more of an impact on timing than a new rotor cap....

https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3Dt0VVtE1BPMs&ved=2ahUKEwikuOXly97gAhUSW q0KHRdUCZYQwqsBMAF6BAgKEAo&usg=AOvVaw3bY_vggbay-dpeTejXj1G9

The bottom 0ring
https://cimg3.ibsrv.net/gimg/www.yot...21cb08e4ac.jpg

Agree...leaking shaft o-ring.

Changing just the cap shouldn't affect timing (the timing is determined by the coils in the distributor, which don't interact with the cap). But if someone shot glue/gasket compound/RTV in there anything could be true. My guess is the timing was never set correctly in the first place, but I wouldn't rule out something more exciting (like a cracked base in the distributor).

In California, having the timing that far off would fail smog, even if the tail pipe emissions could pass. And it's not doing your engine any good to drive it that way. I'd use a heat gun (or hair dryer or wait for a sunny day) to warm up the "stuff" to improve your chances to pull the distributor free without damage. Get the replacement o-ring first https://www.rockauto.com/en/catalog/...g+gasket,7148; 87-4runner is probably right and that's all you need.

Two other things could give you that high timing reading.
1) the smog tech didn't short TE1 to E1 in the diag connector. I would assume they know better than that, but it's a possibility
2) The TPS is misadjusted or faulty and not closing the idle switch. (This could also cause your poor idling).

Either one of these will prevent the ECU from going to base timing, and the timing will be all over the place, usually quite a bit higher than the 5 deg base value.

Well, that's a good point. Have you checked the timing yourself? I would still put clearing the RTV "on my list." But if the timing is actually correct you might want to wait for a good time before you start opening cans that may be full of worms.

Honestly there was nothing else changed with the truck since it started idling hard, and this started right around the time when I replaced the cap. I didn't draw the connection because I was just trying to put a part to use and wrapped it up once I saw the truck started and ran. (This is just another thing proving the axiom one ought not tamper with something that isn't broken.) Anyway it seems worthwhile buying an oem cap to replace this one which I believe was non-oem. I know the cap should not change the timing, but if this aftermarket cap is not an exact match to the existing distributor, it doesn't seem improbable to be shifted a number of degrees out of alignment. It is enough of a job breaking the seal on the distributor and sourcing a new o-ring or reliable silicone that it seems worth first just finding an oem cap and trying that.

I did check the timing when the engine was hot, and one thing that stands out was how the mark on the pulley was not stable but bouncing around a bit +/- the 12 deg mark. I must say I forgot to short the T1/E1 jumpers but still think it ought be more stable. I will do this timing light test again the next time it's warmed up with the diagnostic enabled, though I am now trying to drive it as little as possible as I've heard more knocking/wheezing sounds when running. I hope the engine has not been compromised ..

Your paranoid... the cap isn't going to change the timing... period! Drive it...
the old cap might be cracked or something that would make it miss, run crappy but won't change the timing... will NOT change the timing...

sorry, I am not just paranoid: the vehicle will not pass smog and as such cannot be registered -- something is amiss ..

Ah, jeez. Check the timing! Don't forget the jumper, to put it in base mode.

Out of base mode, the timing is supposed to shift around a little (that's the purpose of the knock sensor), though usually not much at idle. If it does bounce a lot with the jumper in, that is a sign of a bad bearing in the distributor.

And while I am not as absolute as 87-4runner, the chance that changing the distributor cap contributed to your problem is VERY remote. Putting the old cap on, or hanging out at O'Reilly, is a waste of your time. There are tools to determine what to do, and you have them! Use them.

22° isnt big enough to scream a MIS plugged high-tension wire, but check the firing order anyway. While your there look for crosstalk on the trigger wire, and leakage in the high-tension wires.

And of course as mentioned it needs to be in base timing mode with the throttle closed.

A +/- 2° shift with the jumper out seems about normal, this happens due to variations in the RPM from load and such. More than that I would suspect the distributor bearing, but it's right there in front of you so check it.