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2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
07-09-2016, 11:23 AM (This post was last modified: 07-09-2016 11:28 AM by Jimmy.)
Post: #1
2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich after intake gasket failure.

Customer calls me. Says truck WAS running great (he's good with knowing running right or not) when all the sudden it sounds and runs terrible and stalled out when he stopped. He got it running again, tried to drive further, temp gauge started climbing, pulled right over, coolant low.
Soooo, turns out intake gasket let loose. Milkshake city all the way to the top of the dip stick! So I did the intake gaskets. Front coolant ports looked really corroded on the intake and heads, obvious long term slow leaks (history of topping up coolant). Cleaned everything up really well, including dumping a ton of used motor oil through the engine to wash it out. Got it all back together, and it runs like CRAP.
Oil is full and looks clean. Coolant is full and looks clean. Exhaust looks clean. It's like the surgery went perfectly, but the patient is now gravely ill! I show misfires rack up high numbers immediately on cylinders 5 and 6 at idle. Higher idle- mostly on 5 only. Fuel trims ST and LT work their way to high negative numbers quickly. I cleaned MAF, no change. It won't run with it disconnected. It does run significantly better with MAP sensor unplugged. It doesn't register any misfire data with MAP unplugged, but it does still seem to misfire but less. I think it just doesn't monitor it with MAP unplugged? It does still show closed loop. Test drive goes pretty good under throttle, mostly idle and min throttle is rough. Feels like all 6 firing for sure under heavy throttle.
With MAP plugged back in, driving is much worse and SES blinks. Clearing codes during drive helps briefly, like fuel trims are making it run worse? MAP data looks normal, based on SNAP ON fast track values, which leave a lot of leadway. No signs of vacuum leaks, above or into crankcase. No knocking or clicking. Codes are for random misfire, one time for both banks too rich, and a fuel sender code (getting the false low fuel light). Before starting this job, scanner showed all monitors complete and no codes except the fuel sender code.
At idle, if I disable fuel injectors one at a time, 5 and 6 does almost nothing. Actually seems to smooth it out a little when disabled. Spark plug 5 looked a little black, plug 3 less black. Compression on those 2 cylinders both at about 120 (not too bad, but not good). Haven't checked others.
And now for the other angle... cam angle that is! Cam retard showed -10. Well I had marked the rotor position very accurately before pulling the distributor, and it dropped back in perfectly. Absolutely 110% positive it did not get it a tooth off! Square shaped, tight fitting hold-down is not adjustable. Not beyond a few degree basically flex it. I rounded out the hole enough to adjust it to zero. No change in how it runs. But now I'm wondering if the timing chain jumped a tooth to make that -10? Like maybe that super charge of coolant into the oil made it jump? LOL That slimy milky crap was all through the intake, all the way out to the air breather! But after cleaning out all the slime, carbon buildup was nothing beyond normal, and I saw no signs of fuel leaking at the 6 legged spider. I'll peak in there with my bore scope next I guess. And check the fuel pressure. Maybe it got shell shocked. Or maybe I've created a problem there. But, anyone have thoughts on a quick way to confirm valve timing without digging into the cover? I will try working the crank and watching the rotor and see if there is a lot of slop. I'm baffled by the fuel trims being driven negative. I even tried unplugging upstream 02 sensors - no difference in misfire. Would bad valve timing = missing air expected = lean out the fuel trims?? Timing chain jump doesn't seem likely to me at all. But the -10 at distributor, and the 120 compression makes me wonder! And again, under decent throttle it seems to run normal. No plug wires crossed... oh wouldn't that have been nice! Thanks if you managed to read all this. Will update what I find : ).
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07-09-2016, 03:37 PM
Post: #2
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
Have a lot of experience with the 4.3 engine (have a fleet of Astro vans) so sounds like you are headed in the right direction, although I have never seen a 4.3 jump a timing chain, and I have many pushing 300k miles.

Here's the only "quick check" I can come up with. There are at least two timing marks in the crank pulley. (some have three) To line up the distributor properly one of those marks must be aligned to the timing case mark that's at the 1 o'clock position and the other must be at the timing case casting mark around the 4 o'clock position. (check with a mirror if needed) The reason for multiple marks is in the van version you have to work from the bottom because there's no clear sight-line from up top. When two marks line up then you put the distributor in at it's mark. The ECM does the rest provided you are not off a tooth. If you are off a tooth or the chain is stretched out the ECM can only correct for maybe 10 degrees before turning on the CEL. If you choose the wrong crankshaft mark you open a can of worms. The right timing to see with a scan tool will be in the +10 to +20 range at idle, so you could be one tooth off and the ECM can only make up so much.

Now, if you were properly aligned on disassembly that would have been the time to check. IOW, before you moved anything. OTOH, the ECM looks at crank position (in the front cover) versus cam position (part of the distributor) so if everything lines up externally a timing chain issue should appear as an issue with crank or cam sensor codes.

BTW, recalling the fuel pressure regulator is located inside the manifold so if that got fouled with messy oil / coolant you may have a fuel pressure issue as well. Fuel should read about 55 psi running and hold near there for a LONG time after the key is shut off.

One last hint: When turning the crank to align your marks go only in one direction, (clockwise) and never back up.

Keep us posted on your progress.
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07-10-2016, 09:26 AM
Post: #3
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
(07-09-2016 03:37 PM)Rupe Wrote:  Have a lot of experience with the 4.3 engine (have a fleet of Astro vans) so sounds like you are headed in the right direction, although I have never seen a 4.3 jump a timing chain, and I have many pushing 300k miles.

Here's the only "quick check" I can come up with. There are at least two timing marks in the crank pulley. (some have three) To line up the distributor properly one of those marks must be aligned to the timing case mark that's at the 1 o'clock position and the other must be at the timing case casting mark around the 4 o'clock position. (check with a mirror if needed) The reason for multiple marks is in the van version you have to work from the bottom because there's no clear sight-line from up top. When two marks line up then you put the distributor in at it's mark. The ECM does the rest provided you are not off a tooth. If you are off a tooth or the chain is stretched out the ECM can only correct for maybe 10 degrees before turning on the CEL. If you choose the wrong crankshaft mark you open a can of worms. The right timing to see with a scan tool will be in the +10 to +20 range at idle, so you could be one tooth off and the ECM can only make up so much.

Now, if you were properly aligned on disassembly that would have been the time to check. IOW, before you moved anything. OTOH, the ECM looks at crank position (in the front cover) versus cam position (part of the distributor) so if everything lines up externally a timing chain issue should appear as an issue with crank or cam sensor codes.

BTW, recalling the fuel pressure regulator is located inside the manifold so if that got fouled with messy oil / coolant you may have a fuel pressure issue as well. Fuel should read about 55 psi running and hold near there for a LONG time after the key is shut off.

One last hint: When turning the crank to align your marks go only in one direction, (clockwise) and never back up.

Keep us posted on your progress.

Thanks Rupe. It will be a day or two before I get back to it. I'm sure I dropped the distributor back in exactly as it came out, and crank did not get moved at all. If it's off a tooth, it must have been to begin with which would means ecm didn't care @ -10. My now slotted holddown gives me about a tooth of adjustment, maybe. Body (plug) and cap (wires) orientation look correct and scan data show cam retard now at zero (was at -10) But what I don't know is if the cam itself got retarded by 10 degrees, and I've only corrected the distributor. But I take it you think that's pretty much impossible... chain would either stay accurate tooth for tooth or be a total failure? Is there a way to accurately observe if valve (rocker arm) movement begins at the right time? Within 10 degrees?? LOL!
Hey, do you know the sprockets number of teeth? I'm wondering how many degrees one tooth off would be.

I'll check for amount of slack in the chain by rotating crank back and forth while watching rotor. Unless it's real sloppy, I'll assume(oh that dangerous word) that valve timing is correct. I suspect the fuel reg is leaking. I should see that with a bore scope in through the throttle body when I cycle the fuel pump and check the fuel pressure.
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07-10-2016, 10:40 AM
Post: #4
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
The problem with checking the valve timing via a degree wheel like the race builders do it is we have no published specs for the stock cam. IOW, unless you have a source for when a valve opens (so many decrees after TDC) it's near impossible to guess. I can tell you from experience that you'll have around 5 - 8 degrees of chain slack on a high mileage engine and the ECM seems to take care of that if all else is set to the marks.... and there is a mark on the rim of the distributor for #1 rotor location. Use that and center your (now slotted) clamp then see what happens. It will seem to run ok a tooth off but the scan numbers will be out in left field and the CEL will be on.

I don't recall the # of teeth on the cam sprocket but as a rule a tooth will be enough to throw things off by more than 25 degrees. Also, once it's got enough slack to skip it will usually do it again, so constantly changing... and usually to a point where it will not start.
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07-10-2016, 12:34 PM
Post: #5
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
Presto detecto problemo!

First, bore scope effort was useless... too many turns to get where I wanted to see.
But, attaching fuel gauge, not a hint of fuel. Thought my fitting wasn't opening the valve. Well, cycling the key I get a quick 65 or so, then falls off to zero as fast as you can imagine. Several key cycles no change. I'm assuming it's dumping it in the intake. I know it's very little volume to deplete the pressure when pump is not running. So I expect it's not returning to the tank. And of course, it's not leaking at my gauge : ). A steady leak into back of intake would certainly explain the fuel trims AND both back cylinders getting misfire. I did start the engine again and watch the pressure. Idle is a good steady 55psi. WOT climbs to about 65. Looks great until key off and instant drop to zero.

I've never done a v6, but have replaced either entire units, or swapped in a good injector on v8's, many years ago. Never saw a leak or pressure problem(other than pump, power, or ground related) before. Am I looking at replacing the whole unit or just the regulator?? Depends on what I see when I get her apart again?

Thanks so much for your input. Can I post pics here at some point or do I need to host them somewhere with links? I'm totally out of date. Getting too old for this stuff : )

BTW, 112K for miles on this. I've got some significant time into it now. Plus parts and hopefully not too much more $ to fix the fuel problem. He's gonna get a pretty big bill for this one. Scary part is, I'm not overly confident in the intake gasket LONG TERM, because the ports surfaces were so corroded. Nothing available to replace that lower intake with, new or used. All discontinued in the new department. And not something you find used on a shelf. I don't pull junk yard crap.
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07-10-2016, 01:45 PM (This post was last modified: 07-10-2016 01:47 PM by Rupe.)
Post: #6
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
I've had good luck with major brand rebuilt injector clusters, which come with the pressure regulator. This beats doing your own bench rebuilding with remanufactured parts, which is just too time consuming. That said, pay attention to the hose routing. (take a picture works well) One hose goes around another in a weird fashion so everything clears on reassembly... and it's really a tight fit. Changing the cluster should take no more than a few hours all total. (on a van) If you have trouble routing the hoses use a heat gun to soften them a bit and it will fit into the bracket easier.

Here's a tip I found for that cruddy manifold surface. After cleaning it best possible you degrease with brake parts solvent then coat with a thin film of JB Weld to fill in the pit marks, which you allow to harden overnight. In the morning use a flat file or sandpaper on a block to make the surface perfect again. JB Weld will hold up to around 550 degrees, which it will never see in a coolant passage. That said, the aftermarket gaskets seem to seal fairly well anyway, provided you follow the torque sequence. 3 steps up to 135 inch pounds for the bolts going into the heads.

Again, posting pictures here is possible but must be reduced in file size to under 500kb, which will be around 30% of the original with a typical cell phone camera. IOW, save the shot then hit edit and change 100% to 30% then save it again. I did some last night and that will get you near 350kb, which is fine for viewing here. In order to attach the photo you must use the "new reply" button rather than the "quick reply" box found below. At the bottom of that screen there's a box for attachments.
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07-10-2016, 03:57 PM (This post was last modified: 07-10-2016 04:00 PM by Jimmy.)
Post: #7
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
BTWI'll start with seeing what the dealership has to offer.
I think it will be the updated one with wires running along the tubes, if it's like the earlier v8's I've done in the past.
https://www.amazon.com/Standard-Motor-Pr...erado+1500
Link for reference to the style I'm talking about. This one on Amazon is cheap enough, and I thinks it new... but it's chinese... order online... set up for more headache!
I have bench tested them before, just using compressed air over the fuel in the body and jumpers to the pins. Swapped out a leg from another retired unit and had great results.
Anyway, for this intake manifold, I "hand machined" it by using a wet sanding technique I invented myself when I had a blown headgasket on my ATV.
I've got a thick peice of nice flat glass that I clamp to the table and have wet sanding paper glued onto. It was a little heavy and bulky to keep it flat, but I took it down to where the remaining corrosion/pitted areas weren't too low. I have pics of that process, will try to post them later. I figured the old gasket wasn't doing too badly up until it let loose, so this should hold well for awhile. I've seen in the past where they fail but surfaces look fine. I think if the intake was slotted for the gasket (like the plenum), so that it held it laterally instead of the plastic gasket, they would last the life of the motor. I'm just glad I don't have to take but only the top half back apart. I torqued the lower down in about 6 or 7 increments. Very slowly and meticulously, ending at about an extra 10 inch Lbs for good measure. Also used blue loctite. Time will tell. Will keep the JBWeld idea for future! Is there one specifically for aluminum or is it just plain old JBWeld?
BTW... by benchtesting, I meant for function and finding a dead one. I've never attempted any sort of balance testing, although I considered it at the time. I was going to do one side at a time with my homemade metering setup I made for VW CIS. VW CIS? Mentioned in this forum? Can I get evicted for that? : )
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07-11-2016, 12:27 AM
Post: #8
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
The dealer "OEM" part will be expensive. Up until recently I was able to get Delphi from a local jobber so that's what I have been using for years.

You're not the first guy to come up with a home brew refinishing deal. I have a steel plate I have been using for years and have also had luck using a "air-board sander" from my body shop stock. The JB Weld is more recent since everything is starting to get tired and parts are hard to come by. The original JB Weld product is what I have been using since I looked up the temp specs. They claim it's ok to 550 degrees for a LONG time so even the occasional trip near 250 on a hot day when the driver is not paying attention should be fine. 195 degrees should be a walk in the park.

Personally I feel the failure of these intake gaskets is the base gasket material just goes soft with age. Every one that I have seen leak is also deformed and appears to be mushy in substance. IOW, it falls apart when you try to remove it. I don't think setting it in a machined slot is the answer. More likely the real fix would be to make the intake cast iron like the head then go back to the old fashion composite gasket material. Less of the "expansion / contraction" issue associated with aluminum.

Wanna chat about CIS systems of the early 70s? (ha!) I cut my teeth on the old L-Jetronic stuff and the early VW systems prior to that in the late 60s. Heck, I have forgotten what they called it before they used an air-flow meter. (Bosch electronic FI?) It was "the system" for both Porsche 914 and VW Squareback / Fastback models circa 1968.
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07-12-2016, 09:04 AM
Post: #9
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
Looks like I will get a 19210688 at the dealer for 290.00
Other option locally was Borg Warner 63885 for 9 bucks more!
Not sure if it will come with a bracket, or if it will fit current bracket.
Not much savings on amazon, ebay, or wherever, and many Delco OE unit are reviewed as good but not really Delco. Saw Delphi units costing as much if not much more online.

Funny, I read numerous places that the stock unit fires all injectors at once, not sequentially... very misleading. But I imagine moving the control point to the end of the legs makes for much better response time.

CIS? My earliest was a 1979 Rabbit. Plain CIS. Completely mechanical except for the electric fuel pump. Then my later ones were CIS Lambda. Prone to the electrical problem of the whole vehicle electrical problems!

LOL went from chevy trouble to vw trouble. My boring early 90's Camrys almost never have troubles : )
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07-15-2016, 08:15 AM
Post: #10
RE: 2001 silverado 4.3 V6 auto... QUICK method to check valve timing?? Rough and rich a
New fuel injector works great!
All in all, total success. Now comes the test of time for the crappy manifold...


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