MileHighSierra

Hey there. Have 201k miles on my 2000 ECSB 5.3 Sierra. Just changed plugs and wires to see if it would mitigate this random P0137 and P0157 O2 sensor codes I get, to no avail.
If i drive around at partial throttle, the codes never seem to get set off. It's only if i get on the highway and go WOT that the codes get set off.

After driving around a bit more, the codes fall off and the CEL goes away.

I do have Torque Pro and an ELM327......I don't get any misfire codes, although I do notice that on cold starts the truck runs slightly rough.
Could this be the intake gasket manifold issue? Are the cats bad and that's why the Bank 1/2 Sensor 2 codes get thrown?

I was told that these codes do not affect fuel trim or how the truck should run. It generally runs great, although I notice from time to time a stumble when I try to go WOT in certain situations.
Any ideas/experiences you guys have had with these would be helpful. Thanks!

MileHighSierra

Also, I notice that my Knock Retard can be up to 7 degrees of timing at 30-50% throttle under load. I use 85 octane.....as I am at 5300ft and that's what we have for base fuel.
Essentially, my dynamic compression ratio goes from 9.5:1 to about 8.0:1 here at altitude. I have run 91 and I don't really see a difference in KR.

1FastBrick

iTrader: (17)

Are the bank 2 sensors switching at all. They won't be as predominant as the front ones but you should see a change.

Likely it's the sensors.

The knock is likely a false knock as it has been a common issue on the earlier 99-00 trucks.

Have you run any fuel injection cleaner through it?

MileHighSierra

I have actually looked at the O2 volts with Torque Pro. Honestly, the #2 O2 sensor doesn't seem like it switches very well. I will maybe log it here tonight and then screenshot and post the picture so you could take a look.

Haven't had any fuel injection cleaner through it. I am a petroleum engineer by trade, so a lot of the solvents I find in those cleaners I find a little be too caustic for my liking (diethyl ether being one of the compounds).

What are typical timing figures you should see at WOT and partial throttle for these 99-00 trucks? I'm seeing 27-30* of timing.....and even high at partial throttle.

MileHighSierra

Has anyone had a MAF been bad that doesn't necessarily throw a code? I logged my MAF results and it is not a square wave curve. This is just the mass rate and not the voltage from Torque pro.

Is there anyway to monitor fuel pressure with Torque Pro? I have the GM PID's loaded, but it doesn't seem to want to give me rail pressure, etc.

Thanks!

1FastBrick

iTrader: (17)

Yes, I had a bad maf with no codes. How ever my truck is flex fuel. It kept trying to compensate for the difference.

The 2000 does not have a fuel pressure reference that's why it doesn't work on the App.

The rear 02's are generally very slow to compensate. How ever sometimes they can stick all together or not go past a certain value. I have ran several types of fuel injection cleaner through my truck as well as performing things similar to the seafoam treatment through the intake.

Most concentrates or cleaner formulas are designed to be mixed with up to 20 gallons of fuel. The silverado being 26 gallons means it is diluting it that much more.

Given your field maybe you can get your hands on pure Techron.

The carbon build up in the early motors can cause the knock retard. However the software has also been an issue in the performance world with guess seeing false knock.

As far as the lean code, the intake gaskets usually fail and it's usually toward the bottom side making it difficult to locate or test for. The OEM rubber compresses down and starts to take its compressed shape. Over time with repeated exposure to the ethanol and other solvents in the fuel, it no longer seals. Gm revised the rubber to be more resistant to the ethanol in today's fuels so it retains its shape better.

MileHighSierra

I think that the symptoms kind of add up to being the intake manifold gasket. It seems to run great, and at partial throttle there are no hiccups at all. In fact, the WOT hesitation seems to be somewhat random as well.

1FastBrick

iTrader: (17)

With the milage you have, It's definitely possible. These should be the OEM # 89060413

MileHighSierra

Awesome...thank you so much. It's interesting...the idle quality improves after the engine warms, which would lean towards the gasket improperly sealing. I also think that as vacuum increases with RPM (as I.C.E. are basically air pumps), it must slightly pull extra vacuum and cause the hesitation. If i accelerate smoothly at 80% throttle I don't get the issue.

Thanks a ton. I think one weekend I'll just pull it and check out the top end of the motor.

1FastBrick

iTrader: (17)

Good deal. Keep us posted on what you find.