Bad hydraulic roller lifter?

[travis]

I’m pretty sure I know the answer but want to confirm before I tear back into this thing yet again...

1999 L31 Vortec 350. I haven’t started it since yesterday. Yanked the passenger side valve cover and found several rockers looser than they should be. No bent pushrods, but the #6 intake pushrod can be easily depressed fully with not much effort. Number 8 intake is a bit harder but same thing. None of the others are like this.

Are these lifters junk?

[BillK]

Was it making noise ? Why did you decide to check this ? If it has a lot of miles on it the lifters might be bleeding down when it sits but if it isn't making noise then why mess with it.

[GARY C]

I’m pretty sure I know the answer but want to confirm before I tear back into this thing yet again...

1999 L31 Vortec 350. I haven’t started it since yesterday. Yanked the passenger side valve cover and found several rockers looser than they should be. No bent pushrods, but the #6 intake pushrod can be easily depressed fully with not much effort. Number 8 intake is a bit harder but same thing. None of the others are like this.

Are these lifters junk?

Possibly but not likely unless there was something odd for that year, coming from a GM family mostly surrounded by GM friends I have never known of a valve train related issue. Unless you know the history of the maintenance it's hard to say but my personal abusive treatment has never effected their longevity.

You should be able to search on line to see if there is a theme with that year.

[MadBill]

Presumably, everything was okay yesterday? How long did you let it run? Was it noisy, rough-running, both? A friend has a GM V-6 truck that would often start up noisy and rough- running cold, but usually clear up or be good the next start-up. His problem turned out to be randomly sticking valves.

[travis]

This issue started several weeks ago. Driving home from work the thing suddenly lost a lot of power and was popping out the exhaust at mid to heavy throttle opening.

Bank 2 is running full rich, bank 1 is normal. Fuel pressure is the same as it has always been. I have replaced the intake gaskets, fuel injectors, O2 sensors on bank 2, plugs, wires, and probably a few other things that I’m not remembering at the moment. There is a misfire that is getting progressively worse, which I think is the reason bank 2 is going full rich. At this point the truck won’t pull itself out of my driveway.

This thing has always had a random lifter that would clatter on a cold start but it always cleared within about 20 seconds, then it may not do it again for weeks. Now at least a few lifters are noisy and will not clear up and seem to be getting worse, thus my suspicion that at least one has failed completely. #6 intake is the worst...that cylinder cranks 150 but takes a lot longer to get there than any of the others. They all crank between 150 and 180. Cold idle oil pressure is 60-65psi. No bent pushrods and none of the valve springs appear broken or sagging.

Could 1 cylinder not pulling its weight really throw everything off so badly? I’ve worked on a lot of worn out junk and never seen one behave like this before, but none of them was a Vortec engine either. Me trying to learn on something made within the last 20 years is sending me on a wild goose chase it feels like.

All the bank 2 plugs are reading stupid rich, except #6 which is the oddball. Only half the plug is reading rich.

21338844-0E23-4BF8-972F-9FB06FDCE08E.jpeg

[travis]

I’m pretty sure I know the answer but want to confirm before I tear back into this thing yet again...

1999 L31 Vortec 350. I haven’t started it since yesterday. Yanked the passenger side valve cover and found several rockers looser than they should be. No bent pushrods, but the #6 intake pushrod can be easily depressed fully with not much effort. Number 8 intake is a bit harder but same thing. None of the others are like this.

Are these lifters junk?

Possibly but not likely unless there was something odd for that year, coming from a GM family mostly surrounded by GM friends I have never known of a valve train related issue. Unless you know the history of the maintenance it's hard to say but my personal abusive treatment has never effected their longevity.

You should be able to search on line to see if there is a theme with that year.

I don’t know if it’s common, but a friend of mine purchased a brand new ‘99 Silverado and had issues with random lifter clatter as well. All the lifters was replaced under warranty.

[GARY C]

I’m pretty sure I know the answer but want to confirm before I tear back into this thing yet again...

1999 L31 Vortec 350. I haven’t started it since yesterday. Yanked the passenger side valve cover and found several rockers looser than they should be. No bent pushrods, but the #6 intake pushrod can be easily depressed fully with not much effort. Number 8 intake is a bit harder but same thing. None of the others are like this.

Are these lifters junk?

Possibly but not likely unless there was something odd for that year, coming from a GM family mostly surrounded by GM friends I have never known of a valve train related issue. Unless you know the history of the maintenance it's hard to say but my personal abusive treatment has never effected their longevity.

You should be able to search on line to see if there is a theme with that year.

I don’t know if it’s common, but a friend of mine purchased a brand new ‘99 Silverado and had issues with random lifter clatter as well. All the lifters was replaced under warranty.

Was it an LS? some of the early LS engines had an issue with lifter to block clearance and noise, I bought a 2001 2500 HD 6.0 gas with 199,000 miles that had lifter noise (sounded like a diesel) still had the noise when my nephew gave it away at 360,000 miles but never had an issue as far as running.

[BillK]

Travis,

Those engines are pretty bulletproof. I have a 99 Tahoe I bought new. It has 250K on it and still runs like a top.

If it is running as badly as you describe it should be setting some misfire codes. Is the "service engine soon " light on ? Does the light work ? Are there any codes stored ? What is the actual fuel pressure ?

I sort of question the 150 - 180 lbs compression ? That sounds a little high for an 9.5 to 1 engine.

Have you actually checked the ignition timing ? I think those engines had a problem with distributor gears stripping but I wouldn't think it would even start if that was the case.

The only two times my Tahoe has left me sitting have been fuel pump failures. The first time it acted just like yours is. Second time it just stopped completely.

I think you need to ignore the valve train for right now and do some more troubleshooting. Lifters don't usually just fail all of a sudden. I would place my bets on a fuel issue. Any chance you got some crappy gas ? Can you pump some out into a glass jar and let it settle to make sure it isn't full of water ?

Just thinking out loud

[makin chips]

This issue started several weeks ago. Driving home from work the thing suddenly lost a lot of power and was popping out the exhaust at mid to heavy throttle opening.

Bank 2 is running full rich, bank 1 is normal. Fuel pressure is the same as it has always been. I have replaced the intake gaskets, fuel injectors, O2 sensors on bank 2, plugs, wires, and probably a few other things that I’m not remembering at the moment. There is a misfire that is getting progressively worse, which I think is the reason bank 2 is going full rich. At this point the truck won’t pull itself out of my driveway.

This thing has always had a random lifter that would clatter on a cold start but it always cleared within about 20 seconds, then it may not do it again for weeks. Now at least a few lifters are noisy and will not clear up and seem to be getting worse, thus my suspicion that at least one has failed completely. #6 intake is the worst...that cylinder cranks 150 but takes a lot longer to get there than any of the others. They all crank between 150 and 180. Cold idle oil pressure is 60-65psi. No bent pushrods and none of the valve springs appear broken or sagging.

Could 1 cylinder not pulling its weight really throw everything off so badly? I’ve worked on a lot of worn out junk and never seen one behave like this before, but none of them was a Vortec engine either. Me trying to learn on something made within the last 20 years is sending me on a wild goose chase it feels like.

All the bank 2 plugs are reading stupid rich, except #6 which is the oddball. Only half the plug is reading rich.

21338844-0E23-4BF8-972F-9FB06FDCE08E.jpeg

Could onjy having one cylinder being down on compression only cause that? I say no. I had 150 on 5 cylinders and 100 on the 6th and it ran the fastest 1/4 mile time it ever ran in that, condition. 2001 Vortec 4.3L V6. Same engine minus 2 cylinders.

[travis]

Travis,

Those engines are pretty bulletproof. I have a 99 Tahoe I bought new. It has 250K on it and still runs like a top.

If it is running as badly as you describe it should be setting some misfire codes. Is the "service engine soon " light on ? Does the light work ? Are there any codes stored ? What is the actual fuel pressure ?

I sort of question the 150 - 180 lbs compression ? That sounds a little high for an 9.5 to 1 engine.

Have you actually checked the ignition timing ? I think those engines had a problem with distributor gears stripping but I wouldn't think it would even start if that was the case.

The only two times my Tahoe has left me sitting have been fuel pump failures. The first time it acted just like yours is. Second time it just stopped completely.

I think you need to ignore the valve train for right now and do some more troubleshooting. Lifters don't usually just fail all of a sudden. I would place my bets on a fuel issue. Any chance you got some crappy gas ? Can you pump some out into a glass jar and let it settle to make sure it isn't full of water ?

Just thinking out loud

It’s throwing a P0174 code...bank 2 lean condition, and is maxing out the fuel trim on that side. The plugs in bank 1 look perfectly normal.

The 180 psi cranking compression is about what I would expect with a factory rated 9.4-1 engine with the stock cam.

Fuel pressure is 55-58 psi at idle.

I haven’t really considered fuel or anything else common between the banks because everything on the drivers side has normal scan tool readings and the plugs look normal.

[rfast racing]

Check fuel pressure regulator when they go bad on them they send a lot of fuel to cylinder 6 and 8 because of the location. You can push the throttle all the way open look through the throttle body with a bore scope and have someone turn the key on and see the fuel run out of the little tube. Also another sign is the intake will be clean around the pressure regulator

[BillK]

rfasts suggestion on the regulator is a part I forgot. What does the pressure do when you turn the engine off ? It should hold for a few minutes. If it drops down to zero almost immediately then the regulator is most likely the problem.

[novafornow]

All being said, as far as lifter failure, it happens. Had a one fail in less than 500 miles.

[travis]

The FPR was replaced when I replaced the injectors, but both the old one and the new one hold pressure fine.

Distributor gear still looks brand new...I suspect the distributor was replaced at some point. Cam and crank position sensors have been replaced recently (different issue). I have tested the MAF and TPS (both test good), plugged the few vacuum ports, and checked multiple times for vacuum leaks. I can’t find a vacuum leak anywhere, which makes me think a misfire is causing the O2 sensors to read lean, which in turn is making the computer to try to compensate by cranking up the fuel trims on bank 2, which is causing bank 2 to run stupid rich. I may be completely off here though and just grasping at straws at this point.

The engine still starts at the flick of the key. The truck has 294k miles on it...the engine was supposedly rebuilt about 90k miles ago (as all used cars on Craigslist are ). Someone has been in the engine before I got it 4 years ago...the internals are really clean and there are globs of silicon squished out around the timing cover and oil pan, although someone may just have fixed an oil leak. Oil pressure is still great. I have run the engine in the dark looking for spark jumping. I’m out of ideas at this point.

There are no other codes being thrown. Maybe the computer failed? With the valvetrain noise getting worse and not quieting down I’m leaning towards at least 1 lifter being the issue.

[travis]

Possibly but not likely unless there was something odd for that year, coming from a GM family mostly surrounded by GM friends I have never known of a valve train related issue. Unless you know the history of the maintenance it's hard to say but my personal abusive treatment has never effected their longevity.

You should be able to search on line to see if there is a theme with that year.

I don’t know if it’s common, but a friend of mine purchased a brand new ‘99 Silverado and had issues with random lifter clatter as well. All the lifters was replaced under warranty.

Was it an LS? some of the early LS engines had an issue with lifter to block clearance and noise, I bought a 2001 2500 HD 6.0 gas with 199,000 miles that had lifter noise (sounded like a diesel) still had the noise when my nephew gave it away at 360,000 miles but never had an issue as far as running.

It was a ‘98, with the L31 in it. I spoke with him this morning...he still has the truck and it has 270k miles on it now