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OB1214

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Deposits like that at 7k aren't exactly normal BUT could be in your case. Not knowing how the engine was treated and maintained in the past could be indicative of carbon deposits being burnt up since you've put the effort into making the truck happy with new parts. Taking into consideration the evap issue you're having, and not having a quality part, in theory could be your exact issue. Since the new parts fixed it for a minute, get a good one and see what happens after that.

Here's what I'd do before changing parts. Give it the ol' Italian tune-up. Put it to the floor. Do it for Dale. Get that old gunk burnt out. Sometimes it's that simple. A lot of us tend to think more than we should. Being a former European car tech and dealing with those difficulties, sometimes the simple things go overlooked because you know too much. The simple things become complicated because what's actually just a bad coil pack makes your brain think capacitors in the ecm.

Schurkey, what oil and filters do you use? How did your tests come back? We all know modern oil can do it and the filter is the failure point, which you're obviously smart enough to abide by. I'm sure we've all speculated trying it but I surely don't have the stuff between my legs to actually try it!
The truck needed all those parts as all the electronic sensors were not reading when I hooked top my scan tool and read the live data. Those spark plugs I put in when I first got the truck. I know for a fact the truck was well maintained previously, however it was sitting for 5 years prior to my purchase. If you look at my meet Roxy thread you can see a picture when I took off my valve covers off and see that there was NO sludge. Indicting regular oil changes. This was a fleet vehicle prior so it went in every couple of months for inspection, oil changes, etc.
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Schurkey

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26,000 miles on an oil change. Now thats how you kill your motor.
Well, that engine only has 260K miles on it, so you're right--I don't know how extended drain intervals will work out long-term. The lab says the oil is still fit for use. So far, so good.

the motor looks, and is within all top end specs, just like a new motor that rolled off the showroom floor.
You don't know that. You have not tested all that. You SUSPECT all that.

I'm making compression, EVERYTHING in the cylinder is sealed; if a valve seal or stem seal or rings were bad I wouldn't be making compression, and I will also have excessive amounts of blow by. Also note I don't have any blow by in the crank case.
Valve stem seals don't affect compression. You cannot test valve stem seals with a compression tester.

Rings can allow oil IN to the combustion chamber without lowering cranking compression pressure or producing excessive blow-by. Good cranking compression does NOT rule out rings allowing oil into the chamber.

GM was trying to make their emissions tighter and gapped the plugs much bigger, which actually made the motor run like poop he said to gap them at 45 thousands.
1. GM certified and warrantied those engines to run on .060 plug gap. If they misfired, emissions would go up and they'd be in violation of EPA regulations. I'm not thrilled with .060 gaps; I avoid using that big a gap on my vehicles. I don't recommend .060 gaps on any modified engine that runs hard. HOWEVER, that is NOT the problem in this case.

2. If you put in a new set of fine-wire plugs, changing the factory gap is a mistake. You can RUIN those plugs by re-gapping.

He also said that the plugs were mostly due to lean condition and that my timing was fine.
"Lean" plugs run clean, with the porcelains bright-white. Computer-controlled engines, running at 14.7 AFR have clean plugs with bright-white porcelains until the plugs have got a zillion miles on them, and then they're light-grey.

7000 miles on plugs, and the porcelains are crusty? SOMETHING is in the combustion chamber that shouldn't be.

He did tell me that since it have a little shake in the idle and not at 1000, 2000, 3000 etc it's mostly because there's "slop" in the timing chain at an idle, and the chain becomes tighter as the motor revs up. I will be looking at this with a timing light and lock out the advance timing in the distributor.
There is no advance in the distributor. The advance is electronic.

Slop in the timing chain? Maybe. But he hasn't tested for it. He's guessing.

The fuel trim definitely went down because I regapped the plugs to 47 thousands.
Doesn't make sense. The plugs may have been faulty, but the gap--by itself--was not the problem. Have you used a spark-tester calibrated for HEI to verify that the coil isn't partially-failed?
 

WhiteUCF

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The truck needed all those parts as all the electronic sensors were not reading when I hooked top my scan tool and read the live data. Those spark plugs I put in when I first got the truck. I know for a fact the truck was well maintained previously, however it was sitting for 5 years prior to my purchase. If you look at my meet Roxy thread you can see a picture when I took off my valve covers off and see that there was NO sludge. Indicting regular oil changes. This was a fleet vehicle prior so it went in every couple of months for inspection, oil changes, etc.
OB1214

What I was trying to get at was more along the lines of the quality of fuel and oil that was used in the past. Most fleet vehicles don't get the tlc you're giving it. They're just maintained. Especially if it's just a run around vehicle. A clean top end doesn't necessarily have any bearing on how the combustion chamber looks. I should've elaborated more.

I'm gonna check out your other thread now while I finish my coffee!
 

OB1214

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After regapping the sparkplugs to 47 thousands the truck had better fuel econ. If you look at my long-term fuel trims they went significantly farther down at certain engine speeds. The motor just sounded better when cruising, not as loud in the cab. However, after driving 175 miles, the motor had a slight random shake. Nothing to be worried about. I will be catching up with some more reading in the service manuals to see what I could test. I will be pulling some of the plugs out in a couple of days and seeing what they look like.
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OB1214

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Any update?
Not really, unfortunately. For the past few weeks, I was studying for finals (Already got all my grades and passed all my classes this semester :)). I just got home from school a couple of days and it was pouring rain. Hopefully tomorrow I can get out there. I was doing some reading the other day and found out that there is no EST bypass for the '96. Can anyone confirm? I have read the only way to set the timing is with a TECH 2 and or the PID for Cam Timing. If anyone has the PID for the cam timing please let me know what it is. I am using an OBDII wifi dongle with the Torque Pro App. I will be checking for slop in the timing chain by rotating the crank and looking at the distributor rotor and seeing if they move in sync. I suspect there is slop if so, does anyone have recommendations for a timing set. I would prefer a double roller. Has anyone done this, and if so are there any clearance issues and such? Please let me know.
I know that I will need to drop the pan too for taking off the timing cover, this will be a plus since the pan gasket has an extremely slow leak. (The pan is a little wet and I only add about a quarter to half a quart in between oil changes). If anyone has any tips on dropping the front diff and steering. please let me know.
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Schurkey

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there is no EST bypass for the '96. Can anyone confirm? I have read the only way to set the timing is with a TECH 2 and or the PID for Cam Timing.
There is NO way to adjust ignition timing. Turning the distributor DOES NOT change the ignition timing. It changes the alignment of the crank sensor signal to the cam sensor signal, so that they are synchronized. This makes the computer happy. Also assures that the rotor-tip-to-distributor-cap alignment is optimum.

does anyone have recommendations for a timing set. I would prefer a double roller. Has anyone done this, and if so are there any clearance issues and such? Please let me know.
Good luck with a double roller. The reluctor for the crank sensor takes up the room needed for the extra-wide timing chain.
 

OB1214

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After hooking up a Snap-on scanner that I borrowed, I was able to read the cam retard. The retard was -2* which is within spec of -2* to 2*. Yes ideally it should be zero, but dropping a distributor in without a scan tool and minimal tools up at school, I would say that's pretty good. After confirming this I decided to take the distributor cap off and rotate the crank and unfortunately, I will need to replace the timing chain as the rotor lagged way behind, probably in the ballpark of 20 to 25 degrees. I am looking at a Cloyes double roller CLO-9-3510TX9. All gaskets will be replaced with only the best, Fel-Pro.
My goal is to have to timing set replaced within the next month.
A little over a month ago, I went to a local junkyard and got some new air core motors. I replaced my oil pressure gauge but think it may be a little off. Tomorrow I plan to confirm good oil pressure and adjust my gauge if needed. If my oil pressure is good, I will follow through with the timing set.
I'll post my reportings soon.
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Schurkey

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After hooking up a Snap-on scanner that I borrowed, I was able to read the cam retard. The retard was -2* which is within spec of -2* to 2*. Yes ideally it should be zero, but dropping a distributor in without a scan tool and minimal tools up at school, I would say that's pretty good.
Agreed.

I decided to take the distributor cap off and rotate the crank and unfortunately, I will need to replace the timing chain as the rotor lagged way behind, probably in the ballpark of 20 to 25 degrees. I am looking at a Cloyes double roller CLO-9-3510TX9.
1. That timing set is wrong for factory roller-lifter camshafts.

2. 20 to 25 degrees of slop? WOW! I've never seen a running engine with that much slop in the chain. Are you SURE that the distributor gear/cam gear aren't worn?

3. I'm deeply suspicious of timing sets with roller thrust-bearings. If the bearing dies, you've put a dozen teeny-tiny needle bearings into the oil pan, after first getting past the timing chain. If they get caught in the chain, they could cause real problems. If they get past the screen/mesh on the oil pump pickup, they could cause real problems.
 
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