[mike 96 ws6]

This 98 Chevy Tahoe has ~200k miles but it still runs good other than a rough idle. The only powertrain code is p1345- (scanner current code screen capture here)
Today I found the reason for the rough idle - the fuel meter/injectors assembly (aka 'spider') is leaking fuel into the #6 and #8 intake ports therefore flooding/fouling plugs on these cylinders and causing a miss at idle-to-part throttle. I ordered the parts today/be here in the am.
And I'm thinking the code p1345 is partially caused by a worn timing chain or slack in the distributor drive geartrain combined with the rough idle. And I'm hoping the code will go away after repairing the fuel meter/injector leak. But if not, what next?
#1 - should I loosen the distributor and set cam sensor timing (spec = +/- 2 degrees)? (note, distributor has never been loosened/adjusted since factory new)
or
#2 - should I relearn the crankshaft position?
... obviously a new timing chain, distributor geartrain, or whole new motor ect is in order for this truck but I don't have the $ and I need this truck running tommorrow till October if possible...

As always, thanks for any help!
Mike

[sbchevfreak]

Likely chain stretch. Does your AutoEnginuity have the ability to do crank retard angle adjustment?

[LATECH]

Most of the P1345 I have repaired have been a worn dizzy gear.

[mike 96 ws6]

Originally Posted by sbchevfreak

Likely chain stretch. Does your AutoEnginuity have the ability to do crank retard angle adjustment?

I don't recall seeing "crank retard angle" but I'll check tommorrow and post back here. I do know it will do 'crank position sensor relearn'. Is that what your asking?

I installed the new fuel meter/injector assembly today and cleared the codes but P1345 set again as soon as I cranked it up. The camshaft sensor retard (listed as CMP with Autoenginuity) was at 23 degrees (above 1000 rpm) so I tried to adjust it via loosening/turning the distributor. I could not adjust it to spec (0, +/- 2 degrees) since the cap was hitting the fuel supply lines. So I removed the distibutor and re-installed with the shaft 1 tooth towards clockwise. Then I couldn't get the cam retard above -45 degrees. I must have accidentally moved it 2 teeth or something. It was dark and I was tired and I lost one of the cap screws so I quit until tomorrow.
I'll have more information tomorrow.

Originally Posted by latech

Most of the P1345 I have repaired have been a worn dizzy gear.

That's good to know. I'd rather replace the dist gear than the timing chain.

Thanks for the help guy's!!! I'll post tomorrow with an update.

[LATECH]

When you get the dizzy installed look at the cam retard value, IIRC -7 or less is where you wanna be, but check it to be sure. I dont have tech support to check the actual spec. (not at the moment anyhow)
The procedure is called cam crank position correlation relearn. The scanner function/relearn wont allow you to perform the function unless you are within range first with the dizzy.
Put the gear on drop the dizzy in and get it on .
Different scanners/equiptment may call the procedure by a different name. no one wrong here. All good info.

[mike 96 ws6]

Originally Posted by mike 96 ws6

I installed the new fuel meter/injector assembly today and cleared the codes but P1345 set again as soon as I cranked it up. The camshaft sensor retard (listed as CMP with Autoenginuity) was at 23 degrees (above 1000 rpm) so I tried to adjust it via loosening/turning the distributor. I could not adjust it to spec (0, +/- 2 degrees) since the cap was hitting the fuel supply lines. So I removed the distibutor and re-installed with the shaft 1 tooth towards clockwise. Then I couldn't get the cam retard above -45 degrees. I must have accidentally moved it 2 teeth or something. It was dark and I was tired and I lost one of the cap screws so I quit until tomorrow.
I'll have more information tomorrow.

Just to follow up on my post:
The problem I had not being able to get the cam retard within 23 degrees-to-negative 45 degrees was because I didn't have the connector plugged in. Brain fart on my part. As I said I was tired and working in the dark.

Yesterday, after I realized this I was able to re-install the distributor 1 tooth ccw and set the cam sensor retart to spec with no problem.

But I have a new problem. Now I'm getting a misfire code for #6 and random misfire. The scanner shows some misfire on #4 as well. Both cylinders only misfire at idle or low rpm acceleration. The compression on #6 cylinder is 50 lbs. I'm thinking that the raw gas being pumped into #6 cylinder for so long has either washed the rings down or the valve guides, or both. Now that the spark plug is not fouling and the intake charge is correct, #6 is firing, but is firing past the valves causing #4 to misfire as well.
Does this sound like a correct analogy?
I guess that head will need to come off to repair the valve damage, but what about washed down rings? There is no blue smoke from the exhaust indicating a washed down oil control ring. So will repairing the head be enough to get it running smooth?
Thanks again!
Mike

[LATECH]

You need to determine if it is rings or valves. Do a "wet" test on the low cylinder. You know, put in some oil to seal the rings. If the compression jumps up a bunch then the trouble would be rings and would mean a tear down of the engine. If you get little or no significant gain in compression then either the head gasket or a valve comes into play.
When tearing down, you can back off the valves on the cylinder in question and air charge the cylinder to find if it is coming out the intake or exhaust or crankcase. Out the intake is intake valve, out the exhaust is exhaust valve, out the oil fill (crankcase) will be rings or head gasket. If the wet test revealed no increase in compression and the air charge test reveals it come from the crankcase then it would be the head gasket blown into the oil return area.

[mike 96 ws6]

Thanks for the excellent info latech. I knew all this stuff when I worked on vehicles for a living years ago, but I'm getting senile and rarely work on vehicles now days (if possible). But this Tahoe belongs to a good friend and he's spent a bunch of $ to get it fixed by a couple of local shade tree mechanics with no joy.
I'll re-test compression tomorrow with oil in the cylinder and post the results, then we'll go from there.

[sbchevfreak]

yeah, meant cam retard, sorry.

[mike 96 ws6]

Originally Posted by sbchevfreak

yeah, meant cam retard, sorry.

Originally Posted by latech

no one wrong here. All good info.

All good!!!

I pumped 2.6 oz of 2 stroke mix oil into #6 spark plug hole with the piston coming up on the compression stroke and tested compression = no significant difference when cranking the motor (ignition disabled). Then I pumped 2.6 x 2 = 5.2 oz with #6 at bottom dead center coming up on compression stroke = no significant difference.
So I pulled the heads and leak tested = #6 held gasoline in the chamber for less the 15 seconds. All other chambers held gas fine. I found #6 exhaust valve burnt and the guide badly worn. The heads are at the machine shop and I hope to get them back later today.
#6 cylinder wall shows some signs of wash, but the rings are holding gasoline (leak down) as well as the other 7, so I'm hoping it will be okay to run.
I'll post the results when I get it back together.

Thanks again to both of you for your help!

Mike

[LATECH]

SWEET.