1998 yukon Mystery p0300 and rough idle still

[exp500]

There are alot of things that can turn the oil pump shaft, such as a steel ruler from a 12 " square. Even your scanner shows you are a tooth off.
What I have noticed on these is that oil pump shaft usually advances when dist removed. I think it may be a Preload/backlash reaction or just removing from the gear too fast.Only once have I restabbed a new dist without moving oil pump.
Line up exactly on Triangle8. Leave dist hold down only slightly loose, just enough to be able to turn it with 2 hands. Set CMP Retard and tighten fully.

 

[OilBurner2003]

Compare them and make sure that dimple orientation on the gear matches your old one but, yeah, I’d try this way.

Compared both distributors, they both line up to where they should. Got the new dist on the pump first try! I was lucky, until it barked off and didn't wanna start. Must have messed up somehow, re-trying now.

 

[OilBurner2003]

There are alot of things that can turn the oil pump shaft, such as a steel ruler from a 12 " square. Even your scanner shows you are a tooth off.
What I have noticed on these is that oil pump shaft usually advances when dist removed. I think it may be a Preload/backlash reaction or just removing from the gear too fast.Only once have I restabbed a new dist without moving oil pump.
Line up exactly on Triangle8. Leave dist hold down only slightly loose, just enough to be able to turn it with 2 hands. Set CMP Retard and tighten fully.

Got it installed and tuned within spec! Finally done! And then the misfires came back. Woohoo! It needed to be done anyway so I'm not worried.

 

[OilBurner2003]

Compare them and make sure that dimple orientation on the gear matches your old one but, yeah, I’d try this way.

It would appear that I have it fine tuned within spec now! God forbid, I’ve never spent so much time on one part before…Now that everything’s installed, I am still noticing misfires. The distributor needed to be changed anyway, so I’m glad I did this. Maybe I should have done the smart thing and replaced the lower intake gaskets while waiting for the distributor...I'm not sure why I didn't do that. Probably had a lot of confidence that the distributor was part of the problem. Anyway, I have the lower intake gaskets, so I can start whenever. I still have fuel trims and stuff like that to read, when I figure out how to read them, or have you fine gentleman read them. But that's where I'm at now.

 

[east302]

Good deal, glad to hear you got that sorted out.

There should be PIDs for short and long term trims for each bank. STFT1, 2, something like that.

Also grab the upstream oxygen sensor voltage reading for both banks. Should be sensor 1 bank 1, bank 2. You should see both going up and down in voltage, neither should be steady.

 

[OilBurner2003]

Good deal, glad to hear you got that sorted out.

There should be PIDs for short and long term trims for each bank. STFT1, 2, something like that.

Also grab the upstream oxygen sensor voltage reading for both banks. Should be sensor 1 bank 1, bank 2. You should see both going up and down in voltage, neither should be steady.

Not sure If I replied, Now that I have the engine running I should be able to graph that. Most likely tomorrow! I'm curious on what the results will be.

 

[OilBurner2003]

Good deal, glad to hear you got that sorted out.

There should be PIDs for short and long term trims for each bank. STFT1, 2, something like that.

Also grab the upstream oxygen sensor voltage reading for both banks. Should be sensor 1 bank 1, bank 2. You should see both going up and down in voltage, neither should be steady

Not sure how to read fuel trims, I may or may not have selected them all because I don’t know which is which. I’m looking for the O2 Sensor voltage now.

Edit: Something caught my eye, not sure if it’s normal or not. All three oxygen sensors are changing voltage when I watch them, except Bank 1 sensor 2. It stays the same while the others change, even when I give it some gas. Stuck at .450? Whatever that means! Figured I should include it.

 

[east302]

Not sure what the banks 3 and 4 are really reading from, but they’re so out of whack that I’d ignore them. Banks 1 and 2 look like more valid numbers and the ones to see.

It’s adding a little more fuel on bank 1 (driver side cylinders 1357) than on bank 2 (both are positive short trims) but when added to the long terms it looks reasonable. I think the target is having one bank’s short plus long term equaling 10% or less. Oxygen sensors are probably fine, then, but it wouldn’t hurt to see if their voltages are switching (about 0.1 to 0.9 volt)

Others can confirm, but nothing stands out as a red flag on those.

I’ve read that you can sort-of confirm an internal intake gasket leak by plugging the oil cap, PCV and breather holes in the valve covers. Crank it and see if you’re getting a large vacuum at the oil dipstick. Never tried it - mine have always leaked externally by the time I saw that something was wrong.

 

[Fless]

Not sure what the banks 3 and 4 are really reading from, but they’re so out of whack that I’d ignore them. Banks 1 and 2 look like more valid numbers and the ones to see.

It’s adding a little more fuel on bank 1 (driver side cylinders 1357) than on bank 2 (both are positive short trims) but when added to the long terms it looks reasonable. I think the target is having one bank’s short plus long term equaling 10% or less. Oxygen sensors are probably fine, then, but it wouldn’t hurt to see if their voltages are switching (about 0.1 to 0.9 volt)

Others can confirm, but nothing stands out as a red flag on those.

I’ve read that you can sort-of confirm an internal intake gasket leak by plugging the oil cap, PCV and breather holes in the valve covers. Crank it and see if you’re getting a large vacuum at the oil dipstick. Never tried it - mine have always leaked externally by the time I saw that something was wrong.

I agree with the upstream sensor fuel trims. Pretty much anything within 10% is good; 5% is great.

Was this at idle or elevated rpm?

 

[OilBurner2003]

Not sure what the banks 3 and 4 are really reading from, but they’re so out of whack that I’d ignore them. Banks 1 and 2 look like more valid numbers and the ones to see.

It’s adding a little more fuel on bank 1 (driver side cylinders 1357) than on bank 2 (both are positive short trims) but when added to the long terms it looks reasonable. I think the target is having one bank’s short plus long term equaling 10% or less. Oxygen sensors are probably fine, then, but it wouldn’t hurt to see if their voltages are switching (about 0.1 to 0.9 volt)

Others can confirm, but nothing stands out as a red flag on those.

I’ve read that you can sort-of confirm an internal intake gasket leak by plugging the oil cap, PCV and breather holes in the valve covers. Crank it and see if you’re getting a large vacuum at the oil dipstick. Never tried it - mine have always leaked externally by the time I saw that something was wrong.

What a interesting way to diagnose. Also can't

I agree with the upstream sensor fuel trims. Pretty much anything within 10% is good; 5% is great.

Was this at idle or elevated rpm?

This was at idle.