Just wanted to share a little story here. Maybe someone will pick up something new and maybe I can get a question or two answered.

The cast:

A customers 1992 Base Pick-up, 4X4, MANual trans, 310000 miles on chassis, 14,000 miles on reman engine.
Me, a 30-year diesel mechanic that has been grudgingly tinkering with a few gassers for the past ten years.

Symptoms: Erratic idle we have been fighting for awhile, but recently, very intermittently burning oil. Like smoke screen type burning that clears up after driving.

So I have checked a few things with the idle over a the past few months and decided that there is a vacuum leak. The PCV valve wiggles in the rock hard grommet, the dipstick is loose, the vacuum line from the throttle body to that valve on the power steering pump (What is that thing for???) has a splice in it and electrical tape around it. It's been drivable, so it's been on the back burner.

But this smoke thing is bad, bad, bad. Gotta take care of it. So it comes to the shop and I pull the #3 and #4 plugs and they are wet and #1 and #2 plugs and they are dry. Also have oil coming out the #3 and #4 exhaust port gasket.

OK, so what can cause oil to burn on just the rear two cylinders? Seized oil rings? Yeah, maybe, but that will be after other things are eliminated. Worn valve guides, or something wrong with the valve stem seals because the rebuilder used cheap parts, or did something wrong? Very possible since we don't know the quality of the rebuild. So lets start there.

Poop off the valve cover and take a look through the valve springs and the seals are in place. OK. I can't really tell if the guides are loose with everything assembled, so lets poop off that rocker assembly. I loosen the bolts a bit at a time, then pull one out and immediately realize I now need to replace the head gasket. Well, that sucks, but it doesn't solve the riddle. Pull off the rocker assembly and #3 intake spring and seal and everything looks good. Hmmm...

Stand there looking and thinking...

Boy, there's alot of places where the oil pools up in here. Where does it drain back? Ah! There is a slot in the front where it drains back over the timing chain, but what about on the back? AHA! With all of the Ultra Black I see maybe the rear drain if blocked by it.

Right, but wrong. I look at the back of the head and it's not Ultra Black blocking the drain, but the guide sleeve from the rear rocker assembly bolt. But did I knock it off? I pull it out and I can see shiny mark where it has been bouncing in there, wearing the aluminum smooth. Mystery solved. When parking uphill, the rear stem seals would get overwhelmed and suck oil. It's not the end of my story, sorry.

So I don't know the complete history on this engine, but after some other guy installed it, he had to put in a new front cover and the Toyota dealer changed the head gasket. Don't ask, I don't know why. A couple of the previous things I have fixed so far are a broken trans to block stiffener, missing bolts for said stiffeners, and installing the main ground wire to the correct side of the motor mount. So this time, I also found a bunch of bolts in the intake to head and exhaust to head were too short. Like they only had 2-3 threads engaged. That's ungood. Oh, yeah, there is one long bolt that goes through the thermostat housing, bolting the intake on. It was never tightened. Like it was backed out three threads. HMMM. That and the short bolts would explain why the coolant was seeping at that gasket. Ya think?

Anyway, these things happen. I've never done anything like that in the past two maybe even three days.

So it all goes back together. Did I mention I'm working alone? Do you know what a PITA it so to get the head off and back on with that timing chain going through it? Yeah. I used a bungee cord to hold it up, then lifted the head a bit and put a cleaned welding rod through it and across the top of the block to hold it. I guess I screwed up somewhere, because after I got it started, it didn't sound quite right and - big duh! I gotta set the timing. So I dust off the timing light and it's retarded. OK, simple enough. Except it isn't. The distributor is all the way advanced. OK, no big deal. Poop off the dizzy and turn it a tooth. HMMM, now it's way advanced and the dizzy is fully retarded. Whale crap! I got the chain off a tooth.

Off with the VC and roll it to TDC and my paint mark is in line with the dimple. I was pretty sure that I kept the chain tight on the crank gear, so what's up? I start rocking the crank back and forth across TDC #1 and I notice that the valves on #4 aren't right. At TDC #1, #4 exhaust valve should just be closing and the intake valve should just be opening. "On the rock" is what my college instructor called it. (Thank You Allan Jackson)

OK, I guess I wasn't as good as I once was. Adjust the chain one tooth, watch the rock... OK, Adjust the chain two teeth the other way. Drop the dizzy, pull the dizzy, turn the dizzy, drop the dizzy. OK, that looks right. All together and fire it up and adjust the timing and BOOM! Runs great.

Whew! No erratic idle anymore.

Next day, start it cold and it idles at about 1200 and slowly lowers the RPM as it warms up, just it should. Fully warm and adjust the idle to about 800 aaaand coolant dripping off of the transmission.

Did I mention it's been a few days since I missed a bolt? Yeah, there is a coolant manifold thingie on the back of the head that the EGR pipe bolts to and I missed the bolt. Can't get my hands in there from the top, but a reachy-grabber thing got the bolt in the hole from underneath and a wobble socket on a long extension got it tight.

New PCV valve and grommet. I'm guessing it was very old or even original since it was so hard. The dipstick I got from the dealer. The seal on it was again, hard and not sealing. I'm not sure it would mess with the idle at all, but I know if you pull the oil fill cap off, the idle changes, so maybe? I also replaced that vacuum hose. The nipple on the TB is 8 MM and on the vacuum thing on the power steering pump is a 7 MM, so I went with some 7 MM silicone hose to stretch over the 8 MM nipple and the other end stretches over the bulb on the nipple so I'm confident in that. So which was causing the idle problem? Was it a combination of all three? Just one? I don't know and don't care. Really, I don't care. Not one bit. Nope, no care here. Except I hate it when I fix something and don't know what I did. OK. I care a little bit. But it's running great now and he will be happy. Next up is pulling the Xfer case in his Chevy for reseal. Then a wheel seal on his dump truck and a lower roller on his dozer and the instrument cluster on his other Chevy and new slacks on his other dump truck, and by then there will be something else that needs attention.

So I had a question, but I don't recall what it was now. Oh well, maybe I'll recall later.

But that's my story. Nothing revalatory or anything spelled like that, but I just thought I'd share for your reading (?Pleasure?).

 

I do have a smartass comment: use the factory service manual.
Timing for instance need a jumper jumpered, else you read advanced.

 

Yep. Used both. Timing didn't change when I put it in, but that was the first time I checked it though the engine sound changed. I'll do it again with and without the jumper.

 

Couple of things...…

Jumper won't take the timing to base if the idle speed is much higher than 850-900. Also jumper won't take timing to base if the Throttle position sensor is not sending the ECU its 'throttle closed' signal.

Once in a blue moon, the idle-up control valve on the power steering pump will fail in such a way that PS fluid is asperated into the intake. This can make smoke.

 

Fun story!

 

Awesome information. Thank you for spreading the word.

I hadn't thought of the valve on the PS pump, but since I only had two plugs wet, I think that would have eliminated that since I would expect all cylinders to be burning the PS fluid. Also, it should do that all the time, not just nose up? A quick check would be to pull the downstream vac hose and check for oil? Not trying to argue anything here, I'm just thinking about troubleshooting tricks.

So that idle up valve, does it sense PS pressure, open up and allow air around the throttle plate, raising RPM?

 

Yes.

Sometimes when oil is introduced from a small orifice, in the middle of the plenum, it will migrate more strongly to the runners downstream.

 

Got it. So it sounds like just because the plugs aren't all aren't wet, doesn't eliminate oil getting sucked into the intake. Ok. I eliminated the brake booster and PCV because of that, but it sounds like I got lucky.