WolfMann

So the story goes, a couple weeks back the truck starts idling rough, the timing mark seems to wander between 5 and 8, couldn't get it to 0, and there's a strange rattling kind of noise, maybe an occasional shudder. So I go through everything I can think of, check the timing guide, check timing chain position (removed cover and reset chain just to be sure, new chain probably less than 1000 miles), adjust valve clearance, measure voltage at battery, adjust distributor position, everything checks out, still no luck, rough idle. Here's where it gets weird, I have to go to town to run some errands, get to the spot where I switch to 2 wheel drive and notice (as I'm unlocking the hubs) that the truck sounds perfect, no noise, no shudder, I pull out the timing light and the things running at 0. Naturally I'm ecstatic but confused, so I set the timing back to 5 and carry on. Truck runs great the rest of the day. Sure enough a few days later the weird idle symptoms return. So now I'm reaching out for advice, I'm not quite sure where to look for the root of this problem, I'm wondering if it's maybe some malfunctioning part of the emissions system (does anyone know of a part, that would cause these problems if not working properly?) It's been getting cold up on the mountain, will cold weather cause these issues? (first winter with the truck). Would an exhaust leak be a likely culprit? Could really use some outside opinions as I'm feeling kind of stumped, any help is appreciated, thanks guys.

Thommo Thompson

why r u running at 0 degrees BTC?
it should be idling about 10-12 shouldnt it?
this post doesnt mention the engine. first rule, seeking advive, tell us what engine. haha :p

WolfMann

83 toyota pickup, 22r long block. Underhood decal says 5°btdc.

Thommo Thompson

yes thats set with the vacuum advance unplugged. thats the industrybstd, all timing settings are vacuum unplugged. with advance on it should be much higher. so when u say its at 5, if that with advance plugged in thats too retarded

Thommo Thompson

ok if timing is ever being retarded to zero, then static timing must be set wrong to begin with. static shoukd be 5.
if something is causing it to drop to differenet static timings, it may be a vacuum leak or a tempremental broken vacuum advance diaphragm or a dodgy bvsv valve which controla the advance vacuum signal.

WolfMann

That would make sense, what happens is I'll set the timing to 5 (both vacuum lines plugged, hot engine, idle about 950) but when I plug the vacuum back into dizzy it stays at 5. If I rev the engine it advances, and when I apply vacuum to the lines with distributor cap off I can see the springs moving, so I assumed thats just how it works, and that it was working ok. Is there a certain part of distributor that relates to idle advance?

WolfMann

I don't want to set it to 0°, but I do want to be able to, know what I mean. I think I'm more wondering, what it is that clicked on that ride to town, the timing mark had been jumping between 5 and 8, and all of a sudden its sitting at 0, and the noise thing really gets me, strange rattle at idle that just disappears the same time this timing thing happens. Could it be an oil pressure thing? Like the chain has a little more slack because lack of pressure behind tensioner? It would explain the noise, but would a chain with a bit of slack cause the wandering timing mark? I would think so right?

slacker

iTrader: (1)

yep .. oil pressure it could be .
are you running the stock oil filter ?

WolfMann

I've been running fram for the last oil change. No problem until recently.

WolfMann

So it mysteriously cleared up again, had almost convinced myself I was imagining things too (these are noisy motors after all). But I get into town and sure enough the thing is running whisper quiet, again the timing mark which wouldnt reach 0 (couldnt turn dizzy anymore) Is sitting at about 2° btdc. Truck runs like this (beautifully) all around town. Just made it back a little while ago. Here's the thing though, on the way back after climbing a steep hill, I noticed the oil light flickering at idle! Would immediately disappear if I gave it a little gas. But I'm now 90% sure my problem is oil pressure related.

WolfMann

So I've got a couple more questions:

I'm intending to pick up an oil pressure gauge to get a more accurate sense of what's going on, can anyone recommend one? Digital or manual? And is it possible to find one with the proper plumbing?

I'm assuming the rattling noise I'd been hearing and the wandering timing mark were the result of the chain not having enough tension. I've read that the tensioner responds to the oil pressure in truck, is this how it works, more pressure more chain tension?

The way it was idling rough for awhile and then cleared up after getting to town makes me think there might have been some sludge or gasket material caught up somewhere that suddenly broke loose. If this is the case can anyone recommend a way to clean oil passages without hot tanking the block? I want to drop oil pan, clean it, and check the screen on oil pump pick up, but I'm worried about missing something in a passage somewhere.

Thanks guys

L5wolvesf

This sounds like a vacuum issue. Are the hoses/connectors as old as the truck?
Have you put a vac gauge on it - maybe set one temporarily in the engine bay so when you pop the hood you can see it.

Also your signature doesn't mention your vehicle info and your location isn't showing.
I mention location because the high altitude compensator is vac operated if you have one.

Thommo Thompson

hang on, u shouldnt want to get it to zwro degrees
it never runs at zero degrees. it should never be at zero unless u have a vacuum retard diaphragm.. the static is 5. so it should be impossible to be less than that. if u set the static at five, ir shoyld inly ever be more than that. if its goins less, then something is broken, likely, the timing chain, or maybe the distributor itself.

WolfMann

L5, a vacuum gauge is probably a good idea, and my first thought was either vacuum or electronic issues. But the thing that makes me think oil is the rattling noise in front, I can't think of an emissions unit that would result in that kind of noise, and I don't think it's it's the water our fuel pump given that it's intermittent.
I'll look into the signature, and getting some of my truck info there.
I'm interested in the altitude factor, I don't have an HAC and am living at about 4500ft. Town is probably 2000ft lower. But I've never noticed a problem with that before. Would be interested in knowing how much of an impact that has on engine performance.

WolfMann

Thommo I've run it at 0 before, I like the way it runs at 5 or 8 better, but Chilton (and possibly Haynes) recommend setting it at 0 (with vacuum advance disconnected) so I believe it should be possible to reach by turning the dizzy. What confused me was despite removing and installing dizzy in several positions, not being able to reach 0, and then after this sudden change finding the timing at/close to 0.

Thommo Thompson

right but with the vacuum plugged in, it should never be at 0. What im saying is, u should never have it in running condition showing 0 degrees. only with vacuum disconnected should u see anything close to 0.
Perhap what you original meant when you said "the timing mark seems to wander between 5 and 8, couldn't get it to 0,", was you couldn't get the static timing to 0 with advance disconnected? is that more correct?
If so, then its possible that an centrifugal; advance spring has come loose in the distributor housing, which would be the reason for the noise and would give a very ad hoc up and down timing reading.
If this is the case, then the reason you cant get it to zero, is because the weights are too easily flung out without the spring to hold them (or one of them) back sending the dizzy into a constant over advanced state.

Thommo Thompson

also, ignore that 0 degrees. its just wrong i was about to start my reply with, "IGNORE HAYNES" haha. but decided to bight my tongue, but then i found this next thread by pure coincidence.
https://www.yotatech.com/forums/f115...timing-165832/

go with 5 when you get it all working.

L5wolvesf

A "rattling noise" up front, that isn't valve clatter does sound like a timing chain issue as the other guy pointed out. Is it constant or intermittent?

If you don't have an HAC then it can't have a vacuum leak from the related hoses. But you could have a vac leak elsewhere. How old are your vac hoses?

WolfMann

Thommo I like to run it at 5 or 8 myself, and I'll take another close look at the dizzy soon. I don't think the noise is coming from there but I'm expecting a mechanics stethoscope in the mail soon, so I should be able to isolate it.
​​​​

WolfMann

L5, I replaced all the old rubber hoses with new silicone ones a couple months ago, they still look brand new. To be fair I haven't gotten to test every single piece of emissions equipment but I've been over most of it. I just cant imagine a faulty piece of emissions making that noise up front.