Unbelieveably Frustrating

[bcfitzsimons]

Well, I'm about at the end of my rope-

 

I brought my 2002 8.1L into my local dealer 2 weeks ago for a warm spark knock for the FIFTH time in 10 months.  Decarbonized the engine, changed the plugs, checked the EGR, fuel injector cycle test, fuel system test, etc.  Nothing panned out.  The dealer called GM Tech Assistance, who sent someone there.  They diagnosed mis-torqued intake manifold bolts, with subsequent loss of vacuum (should they have replaced the gasket? ???)

 

It took one week to diagnose the problem, and then one week to get the new torque-to-spec bolts in.  Picked up the truck today-and the spark knock's STILL there.

 

I've been working with Chevy customer assistance, who's given me a 100000 mile warranty on the engine.  So, I figure, since GM now owns the engine for the next 5 years, I'm going to bring it back Monday.  I kind of feel bad for the dealer-they give their customers a free rental car through Thrifty, and the rental bill was $420, while they only got $210 from GM for the intake bolt switch-

 

Has anyone else had warm spark knock troubles?  The knock's there even with 93 octane in the tank.  Anyone have any suggestions?  Save for demanding a new motor be placed into the truck (only 15000 miles on it!)?

 

Needless to say, I talked to my lawyer right before I wrote this-

 

Any help would be appreciated-

 

Thanks-

Fitz

[bcfitzsimons]

Oh yeah-I figured since the rental car bills will surely outstrip any profit on the part of the dealer for the repair bill, my dealer will probably help me press for a new motor, too-

 

Fitz :angry:

[CMNTMXR81]

Well, of the intake is now bolted down properly and no leaks are present therefore leaning you out, You have to look into the engine itself.

 

Have they checked all valvetrain?  Perhaps theres slack somewhere.  A bad lifter?  Lifter boss broken which isn't holding the lifter in place, bent pushrod, loose rocker

 

If everything in the valvetrain checks out, You may have to go deeper.  How about wrist pins on the piston/connecting rod being bad?  A piston skirt possibly broken?  Both of which could be causing the piston to rock while going up and down in the bore.

 

Either way, it may be cheaper and more advantageous just for them to replace it then tearing it apart, attempting to fix it and hope they get it.

[Tucson_02Silverado]

Could also be a deeper problem as the cam and/or crank was not aligned and the engine is actually pre-advanced.  Thus with standard timing settings is too far advanced.  Try a test by retarding the computer timing at least by 6.  Should be able to be set by a TECH2 tool.  Otherwise front tear down for visual inspection.

[CMNTMXR81]

Yea, good point.  I forgot about that.  Since they are 0 degree BTDC timed, anything retard back will be easily changed.

[bcfitzsimons]

Well, I have to take the truck back to the dealer this week.  Talked to Chevy customer assistance, and they asked for the dealer to do another diagnostic check on the engine.  I don't have a problem with that-if I'm going to ask GM to shell out $ for a new block, the least I can do is allow them to convince themselves that it's the only way to solve this problem.

 

I talked to the service people at my dealer, and they said that they're at a loss as to what to do.  The guys from GM Tech Assistance who went to my dealer to examine my truck could only come up with a loose intake as the cause;  as of this morning, the knock is back, with the same severity as before.  

 

At this point, I really do think it's something deeper in the engine that's causing this.  A misground crank, bad bearing, bent rod, cracked piston-something that expresses itself only under load.

 

Also-the guy at Chevy customer assistance said that depending on what my dealer says, a new engine for my truck may be on the way-

 

Fitz.

[Kania2k1]

When does the noise make itself apparent?  Is it under any acceleration or only at WOT?  I've got a little knock at WOT on 87 and 89, on my 5.3L

[bcfitzsimons]

It makes itself apparent under moderate or WO throttle, just after you dip into it, and then it persists until the tranny downshifts (if it can).  It'll also sometimes happen as you let off the throttle too.

 

Fitz.

[mamachala]

In a Chevy truck forum at Edmunds.com some guys were complaining about piston skirt slap in the 8.1L. Mine only has 8000 miles on it and I'm noticing what I think is preignition. My 160 thermostat is on order, maybe that will help.

[DHuts]

I took my 2500 HD, 6.0 in last week for the 5th time with the same persistent problem. They had a new computer update that took care of the problem! You won't eliminate all spark knock, especially if you pull a trailer, but it sure make my truck run and sound better..

[gtpz71]

I'm not sure if this applies, but you may want to check it out.

 

Service Bulletin: #02-06-04-023A - (06/14/2002)

 

Audible Spark Knock (Detonation), MIL Illuminated, DTC P0332 Set (Replace Rear Bank Knock Sensor and RTV Area Around Sensor) Audible Spark Knock (Detonation), MIL Illuminated, DTC P0332 Set (Replace Rear Bank Knock Sensor and RTV Area Around Sensor)

 

1998-2002 Chevrolet Camaro, Corvette

 

1998-2002 Pontiac Firebird

 

with 5.7L Engine (VIN G -- RPO LS1)

 

1999-2002 Chevrolet Silverado, Suburban, Tahoe

 

2002 Chevrolet Avalance

 

1999-2002 GMC Sierra, Yukon, Yukon XL

 

2002 Cadillac Escalade, Escalade EXT

 

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, Z, N, U -- RPOs LR4, LM7, L59, LQ9, LQ4)

 

This bulletin is being revised to add Cadillac Escalade and Cadillac Escalade EXT to the Models. Please discard Corporate Bulletin Number 02-06-04-023 (Section 6 -- Engine/Propulsion System).

 

 

Condition

Some customers may comment on a mild to severe engine ping (commonly referred to as spark knock), usually worse during acceleration and/or an illuminated MIL. Upon investigation, the technician may find DTC P0332 set.

 

 

Cause

This condition may be the result of corrosion of the rear bank knock sensor due to water intrusion into the sensor cavity. This condition is more apparent on vehicles in which customers frequently wash the engine compartment.

 

 

Correction

Replace the rear bank knock sensor and build a dam (wall) around the sensor using RTV to divert water away from the sensor. Use the procedure and part number listed below.

 

Remove the intake manifold. Refer to the Intake Manifold Replacement procedure in the Engine Controls sub-section of the appropriate Service Manual.

 

 

Remove the wiring harness assembly from the knock sensor.

 

 

Remove the rear bank knock sensor.

Install the new rear bank knock sensor. Tighten

Tighten the knock sensor to 20 N·m(15 lb ft).

 

Install the wiring harness assembly to the knock sensor.

 

 

Apply a bead of RTV silicone sealant approximately 9 mm (3/8 in) wide and 6 mm (1/4 in) high along the outside edge of the ridge on the engine block valley cover around the rear bank knock sensor. DO NOT form a complete circle. Leave the rear section open as shown.

From the underside of the intake manifold, completely remove the rear intake manifold seal (foam material).

Install the intake manifold. Refer to the Intake Manifold Replacement procedure in the Engine Controls sub-section of the appropriate Service Manual.