LEAN on both banks

[cadman777]

Hey Guys,
Thanks for having this forum.
I searched it and others on the internet and still didn't find an answer for my problem.
Maybe someone in here has a known good answer?
Here's what's going on...
It's a 1998 Chevy Tahoe, 5.7L Vortec, 2wd, 4dr, front & rear A/C.
It has no cats and the EGR system is disconnected.
I has a performance cam, but nobody knows what it is.
It still has all 4 O2 sensors.
When it came to me it ran so rich it was choking me to death!
The back tailgate looks like it's a dirty diesel!
So I disconnected all 4 O2 sensors and then did this work on it:
1. cleaned the plugs b/c they were caked up with soot and carbon.
2. 4 of the plugs were about 1/4 of the way unscrewed, and carbon was all built-up in the threads at the head end of the hole.
3. so I cleaned up all the tapped holes (for making a good ground), and reinstalled the 8 plugs
4. before cleaning the plugs, it was misfiring on #8 real bad and on #4 & #2 no so bad but not good.
5. also, bank 2 was the side with all the misfires.
6. after cleaning the plugs, I installed them in random cylinders (no plug went into the same cylinder).
7. now, only #3 has a slight misfire (on the Tech2 scanner).
8. I also flipped the intake adapter seal so it wouldn't leak at the throttle body.
9. I smoke tested it and that was the only leak, which is fixed now (for the most part).
10. the CMP setting was 7 deg @ 1100 RPM, so I fixed that to 0 deg @ over 1000 RPM.
11. it has exhaust headers, and both connections to the head pipes were leaking, so I fixed them with new gaskets and fasteners.
12. the CKP pigtail wire coatings are disintegrating, but I didn't have time to fix that yet.
13. the oil sender (near the distributor) is leaking pretty bad, but waiting on parts to fix that.
14. the rotor, cap and wires were nasty, so I replaced them with a known good set.
15. when the new plugs arrive I'll replace them all too.
16. it passed an Injector Balance test @ about +/- 3 psi.
17. it passed a power balance test and a compression test @ +/- 6 psi (high=190, low=178).
18. the fuel pressure on the rail is a solid 63 psi @ WOT and a solid 53 psi all the rest of the time.
19. the oil is pitch black, but that'll have to wait till I get oil and filter.
20. it had a bunch of DTC's when it came to me, but now it only has P0452 (Evap circuit Low).
21. haven't looked into that yet.
At this point it runs pretty good, not very rich (cp. to before) but you can still feel a regular MISS and the Tech2 says LEAN on both Banks.
And that's with no cats, none of the O2 sensors hooked up (running Open Loop), the EGR system is disconnected (the EGR valve is still hooked up and working), and it has a (mild) performance cam.
So what I'm wondering is what may be causing the LEAN issue.
Anyone have any ideas?
Thanks for your input!

 

[RichLo]

You're going to have to put the upstream O2's back in at the very least. I would add those two to the list on new stuff to buy also, since it was running rich and missing for so long, they are probably shot or close to it.

Your definitely on the right track though! I would also finish everything that you have planned and drive it for a few tanks of gas to let the computer adjust to all of the changes before you over-diagnose it.

The EVAP code is usually just a bad gas cap, or something else making the gas tank pressure go too high or too low. Sometimes the purge solenoid goes bad but I would consider that rare unless it was regularly WAY over-filled and pulling raw gas into the evap canister. EDIT: or somebody deleted all of the EVAP stuff considering what they did to the rest of the emissions components.

 

[cadman777]

Hi Rich,

Thanks for your input.

Yes, I was planning on replacing the 2 fore O2 sensors for that reason.

My thought on running it was to put a can of SeaFoam in the tank and fill-it-up.
Then run it like that to clean some of the coke off the valves, pistons & cylinder heads.

I checked the EVAP solenoids w/the scan tool and they worked.
Fortunately, the owner didn't scrap that part of the system.

So I'll get the O2 sensors, change the oil and filter and oil sender.
The only thing that concerns me about installing 2 new O2 sensors is that the computer will go back to 'loading it up' with fuel when it sees steady LEAN signals on both banks. What do you think about that?

Thanks!

 

[Schurkey]

It's a 1998 Chevy Tahoe, 5.7L Vortec, 2wd, 4dr, front & rear A/C.

It has no cats and the EGR system is disconnected.

That needs to be fixed.

I has a performance cam, but nobody knows what it is.

Would be worth figuring that out. A degree wheel, a dial indicator, pop the valve covers, and spend an afternoon writing down the cam specs. You could get close without even removing the rocker arms 'n' pushrods from #1, if you're careful about setting-up the equipment.

It still has all 4 O2 sensors.

Ancient? Faulty?

I disconnected all 4 O2 sensors

Remove and replace would be better.

then did this work on it:
1. cleaned the plugs b/c they were caked up with soot and carbon.
2. 4 of the plugs were about 1/4 of the way unscrewed, and carbon was all built-up in the threads at the head end of the hole.
3. so I cleaned up all the tapped holes (for making a good ground), and reinstalled the 8 plugs

Probably due for new plugs, but this is a start.

4. before cleaning the plugs, it was misfiring on #8 real bad and on #4 & #2 no so bad but not good.

Misfire makes the O2 sensor(s) crazy. They report false "lean" signals, so the computer tries to enrichen the mixture.

5. also, bank 2 was the side with all the misfires.
6. after cleaning the plugs, I installed them in random cylinders (no plug went into the same cylinder).
7. now, only #3 has a slight misfire (on the Tech2 scanner).

Better, but not there yet. Need to find out why you still have misfire. If you did not have misfire on #3 before...I suspect a faulty spark plug.

But maybe you had #3 misfire before, and it was covered-up by the three misfiring cylinders on the other bank.

8. I also flipped the intake adapter seal so it wouldn't leak at the throttle body.
9. I smoke tested it and that was the only leak, which is fixed now (for the most part).

Is is fixed, or is it not fixed? "(for the most part)" is like being sort-of pregnant.

12. the CKP pigtail wire coatings are disintegrating, but I didn't have time to fix that yet.

That'll need to be fairly high on the list of priorities.

15. when the new plugs arrive I'll replace them all too.

Excellent.

If this was me, I'd be buying plugs with a shorter side electrode, intended for about a .040--.045 gap instead of the .060 GM calls for. But the ignition system--in good condition--will fire a .060 gap. Don't just crush the side electrode down to a .045 gap, though. If you bought .060 plugs, run them at .060.

A smaller gap is easier on the ignition system insulation, and on the ignition coil.

16. it passed an Injector Balance test @ about +/- 3 psi.
17. it passed a power balance test and a compression test @ +/- 6 psi (high=190, low=178).

Describe your "power balance" test. I think it's odd that you have a misfiring cylinder, but it can pass a power-balance test.

20. it had a bunch of DTC's when it came to me, but now it only has P0452 (Evap circuit Low).
21. haven't looked into that yet.

Did you CLEAR the codes intentionally, or did they resolve themselves without you needing to clear them?

but you can still feel a regular MISS

That's gotta get fixed.

and the Tech2 says LEAN on both Banks.
And that's with no cats, none of the O2 sensors hooked up

Means nothing. Without functional upstream O2 sensors, the computer has no idea whether it's rich or lean.

the EGR system is disconnected (the EGR valve is still hooked up and working),

Get the EGR functional again.

Yes, I was planning on replacing the 2 fore O2 sensors for that reason.

Good plan.

My thought on running it was to put a can of SeaFoam in the tank and fill-it-up.
Then run it like that to clean some of the coke off the valves, pistons & cylinder heads.

Good luck. It'll take more than that to clean the deposits. But ARE THERE deposits? How do you know?

The combustion chambers are easily and effectively cleaned by pouring a "urine stream" of water down the throttle body, with the engine at fast idle (throttle blocked partially open.) Water doesn't smoke like petroleum-based solvents, so the neighbors don't call the Fire Department on you.

So I'll get the O2 sensors, change the oil and filter and oil sender.

Get the EGR working, too. Ideally, fresh catalyst(s) and rear O2 sensors as well.

The only thing that concerns me about installing 2 new O2 sensors is that the computer will go back to 'loading it up' with fuel when it sees steady LEAN signals on both banks. What do you think about that?

Misfire causes the O2 sensor to report a false "lean" condition. You had multiple misfires, so I don't doubt the computer was deep into "rich command".

Fix the misfire, it shouldn't be "lean" any more...so the computer won't compensate by throwing excess fuel at it.

 

[0xDEADBEEF]

If it reads lean and smells stinky rich, in my experience that's a dead hole.

 

[cadman777]

0xDEADBEEF, thanks for that idea.​

I did a compression test on all the 'holes', and they call came up between 178 psi and 190 psi.
Didn't do a leak-down test on any of the 'holes'.
So what makes you think it's got a 'dead hole' with all good compression?

 

[0xDEADBEEF]

0xDEADBEEF, thanks for that idea.​

I did a compression test on all the 'holes', and they call came up between 178 psi and 190 psi.
Didn't do a leak-down test on any of the 'holes'.
So what makes you think it's got a 'dead hole' with all good compression?

By dead I mean it's not firing. If a cylinder isn't firing, it's just pushing air (or air and fuel) in the exhaust which makes the computer think it's running lean and needs to add fuel.

 

[cadman777]

Schurkey, thanks for your lengthy reply.​

It ain't my vehicle.
I know for a fact that the owner ain't gonna add EGR and cats.
So I gotta work with what I got.

On the smoke test, after flipping the intake adapter seal, there was a slight smoke trail out of a small area (about 10 degrees around the perimeter). In my book that's good enough to fix that major leak. Besides, the part is discontinued, and you can't get that stupid special double-lip seal. There isn't even an aftermarket pimp making them. But there are some aftermarket intake kits for 400 bux that don't seal worth a s**t.

I thought about doing the 'water clean' and may still do it.
But first I wanted to fix this lean problem.
Not being familiar with how this system works, I came in here for advice and a 'education' on it.
I want to know WHY it's doing this.

Please link me to instructions on how to figure out what the cam timing is.
Thanks.

I read about the plug gap thing, but decided not to do it just yet.
Didn't want to throw that extra change into this mix until it's fixed 'as-is'.

So what do you think can be causing the problem and solution?
I can change the plugs when the arrive, and add O2 sensors.
Other than that, I can't imagine anything else is causing it to misfire...
Unless the the cam opens longer which adds more air to the mixture, resulting in a permanent LEAN mixture?

Better yet, I can post the data/numbers for you to take a look at and tell me what you think it's not right.
Just tell me how to run it when collecting the numbers.
I suck at reading the numbers, b/c I have not training in the basics.

Cheers...

 

[cadman777]

@0xDEADBEEF, OK, thanks for the clarification.​

But since doing all the work, there's only a slight misfire on #3, according to the Tech2 scanner.
Do you know of a more accurate and reliable method for testing for misfire?

 

[RichLo]

What came first, the dead O2 sensor or the fouled spark plug?

Or wait... isnt that saying Chicken or Egg? I forget sometimes

You really need to tell the owner that they need to get it back to 100% on the standard 'tune-up' parts before you can diagnose more. If you keep running it with bad ignition components, smoked O2's, non-functioning EGR and a 'sorta fixed' vacuum leak, you'll never know what the root problem is. Those parts are all cheap... especially since you know they are bad anyway.

The cam without a tune may be suspect but you really need to bring everything else back to 100% first. Dont worry about smoking new O2's or spark plugs by running it a few miles with a possible lean or rich condition. Those are pretty robust components and need thousands or tens of thousands of miles running out of their acceptable range before they foul. The computer needs to find its new status quo before it can tell you more.