Closer_2001

iTrader: (6)

The Wife's '04 L59 Z71 Tahoe, which is relegated to family taxi duty and periodic towing of the 6000# boat has done one heck of a job over the last 3 years...

I picked it up with 95k on the clock in late 2009 from owner #2 including a folder of service records and have bestowed my usual religion of maintenance and detailing ever since. As of the stroke of 2013 - 167k on the odometer.

Over the past few weeks as the temp has dropped, I noticed a rougher than normal idle. Since the TR55s were installed at 96k, I figured it was probably time. As the holidays took their course and the TR's remained in a box on the shelf, the CEL appeared and a quick HPT scan revealed PO171 and PO174. A PT.net search and email with my good friend who runs the service dept at a local Chevy/Caddy dealer netted "Teal Color" intake gaskets in route.

Finally today I took the time to make the swap.

Unfortunately - I was horrified to see all the gunk in the intake and intake ports! This engine has seen documented 3k-5k oil changes since new - Synthetic from this owner. I'm curious if the leaking intake and over-rich fueling may have made this worse ?



Also of interest - I run E85 through this when towing short distance or over 10 tanks or so - look at the spray pattern down the intake ports. Seems something is cleaning the ports...



Interesting to visually see the OE orange gaskets distorted - no wonder they were leaking!



I thoroughly cleaned the intake, head ports, TB and valley - 7 cans of intake cleaner!!

I also ran Seafoam through the top end - which caused minimal smoking (E85 doing it's job)!?, Crankcase (and did a hot oil change) and half a bottle in the fuel.

TR55s should finish out this round of maintenance - goal is taking this one past 10 yrs and 200k miles!

Onetogofast

iTrader: (9)

A little bit of maintenance here and there goes a very long ways!!!

AKlowriderZ71

iTrader: (22)

That all looks very typical to me. I wouldn't be too alarmed about it.

Did you take a look at your knock sensors while you had the intake off?

Closer_2001

iTrader: (6)

I didn't - haven't seen any strange codes or behavior so I didn't even think about it. I bet I can have the intake off in less than 20 min now after doing it though. Hopefully not needed!

KHester84

Proof we can all use a catch can or two on these LS motors

1FastBrick

iTrader: (17)

X2 This is pretty typical. What your seeing is the gas the pools up outside of the spray area and clings to the walls and gums up.

This is why they tell you to use Quality Gas and not just the cheapest you can find. They also recommend the use of Fuel additives every so often to help combat this.

As the injectors start to get the same type of varnish on them, they will start to drip as they open and close. The larger droplets from the drip will cling to the walls and gum up.

They will clean up a bit with some brake clean and a rag. Just be careful not to get derbies in to the ports. You also don't want the cleaning solvent to build up in the cylinder. I would pull the spark plugs out, disconnect the injectors or fuel pump circuit, and also pull the connectors for the coil packs. Then crank it over a few times. This should allow any small derbies to be ejected out the spark plug hole.

Reconnect everything, prime the fuel system, and fire it up. Add some injector cleaner to the tank on the next fill up.

HTH