Missing BigBlock

[Shaners]

My buddy has an 2500 Avalanche with the 8.1L in it.  The truck is about a year old and has about 12K on the odometer.

 

He had it to the dealer last fall for a miss in the engine.

 

The dealer did a top end cleaner, replaced a few spark plugs and wires and 2 of the fuel injectors.  The truck is back to the dealer now for the same problem.

 

Has anyone got an idea what could be the problem???  Is the dealer even looking in the right place???

 

It seems like he is still looking at the injectors being the problem.  I'm wondering if it isn't computer related, possibly something to do with the torque management program used with the 8.1L/4L80E combo.  My buddy says the truck is gutless out of the hole when he pulled a 4-place snowmobile trailer home from Canada yesterday, but seemed to tow OK down the Interstate.

[02 2500 Avalanche]

I would bring the truck to the dealer and hook it up to a Tech2 to see if there are any codes. The TM could be the problem, it could be retarding the timing way too much and killing the power.

 

 Alex

[CMNTMXR81]

If it were a miss in the engine, he should be readily able to feel it and hear it.  Is this the case?

 

I looked up on SI2000 and this is the only thing out there when I entered "Missing" for an 8.1L Avalanche

 

Service Engine Soon Indicator Illuminated, Transmission Slips, Engine Flare, Delayed 2-3 Shift, Shifts Missing, No Shift, DTCs P0730, P0756, P0757 (Replace Accumulator Assembly/Service Transmission) #03-07-30-005 - (02/12/2003)

 

Service Engine Soon Indicator Illuminated, Transmission Slips, Engine Flare, Delayed 2-3 Shift, Shifts Missing, No Shift, DTCs P0730, P0756, P0757 (Replace Accumulator Assembly/Service Transmission, If Necessary)

 

2002 Chevrolet Avalanche, Express, Silverado, Suburban

 

2002 GMC Savana, Sierra, Yukon XL

 

with 4L80E (MT1) or 4L85E (MN8) Automatic Transmission

 

Built Between February 1, 2002 and April 10, 2002

 

Condition

Some customers may comment that the Service Engine Soon Indicator is illuminated, the transmission slips, the 2-3 shift takes too long, or the transmission does not shift properly.

 

Cause

The condition may be due to an improper finish to the bore of the 2-3 accumulator housing, causing damage to the seals.

 

Correction

 

Important

Verify the vehicle build date in GMVIS. If the vehicle build date is between February 1, 2002 and April 10, 2002, proceed with this bulletin. If not within the build date, refer to SI for diagnostic procedures.

 

1) Road test the vehicle with the transmission fluid and engine coolant temperature stabilized at normal operating temperature. Confirm with the Tech 2® that there is a delayed 2-3 shift (greater than 0.45 seconds), or no 3rd gear operation.

 

Important

INSPECTION OF A TRANSMISSION FOR EVIDENCE OF CLUTCH MATERIAL OR FINE METAL DEBRIS IN THE PAN DOES NOT A DIAGNOSIS MAKE. The transmission will have non-magnetic metal in the sediment in the transmission pan. The manufacturing/machining process of the transmission case creates a very fine aluminum dust, which when combined with the cooling/lubricating fluid turns to a paste. Even though attempts are made to remove this completely, some will ultimately be missed and will end up in the transmission fluid reservoir (pan). This paste will always remain in the pan. It can not be picked up and pulled through the filter and affect the operation of the transmission.

 

 

2) Remove the transmission pan and inspect the fluid.

- If the fluid is in good condition, go to step 3.

- If the fluid is burned, go to step 6.

- If there is metallic debris attached to the magnet in the pan, go to step 6.

3) If the fluid is in good condition, remove the accumulator housing assembly and discard the assembly. Refer to SI Document ID #749332 for the procedure to remove. Assemble the new 3/4 accumulator assembly and reinstall the components.

- 3rd and 4th clutch accumulator housing is P/N 8684220.

- 3rd clutch accumulator piston seal is P/N 8661647.

- 3rd clutch accumulator piston is P/N 8683088.

- 3rd clutch accumulator piston inner seal is P/N 8661639.

4) After completing the repair, properly fill the transmission with DEXRON III® Transmission fluid.

5) Continue with Step 10.

6) If the fluid is burned or metallic debris is found attached to the magnet in the pan, the transmission will need to be removed and serviced internally.

 

Important

- All of the transmission internal components need to be removed from the transmission case assembly. The transmission case needs to be cleaned thoroughly before reassembly.

- When reassembling the transmission, it is imperative that the original accumulator housing assembly is discarded and a new assembly is installed.

- For transmission removal and installation procedures, refer to SI Document ID #758291.

- For the transmission overhaul procedure, refer to SI Document ID #658951.

7) Inspect the Direct Clutch and Forward Clutch assemblies. Replace them as required during the reassembly process.

8) Before reinstalling the transmission in the vehicle, use the new Transflow Transmission Cooling System Service Tool J 45096 to flush and flow test the transmission cooling system.

9) Reinstall the transmission and properly fill with DEXRON III® Transmission fluid.

10) Road test the vehicle, performing multiple 2-3 and 3-4 upshifts from a cold start. Confirm with the Tech 2® that 3rd gear is present, and that 2-3 shift times do not exceed 0.40 seconds.

 

Parts

08684220 = Housing, 3 / 4 Accumulator 1

08683088 = Piston, 3rd Clutch Accumulator 1

08661639 = Seal, 3rd Clutch Accumulator Piston Inner 1

08661647 = Seal, 3rd 4th Clutch Accumulator Piston 1

[Shaners]

Thanks for the info. but he hasn't had any tranny complaints.  He did say the "service engine" light came on coming back from Canada.  The first time this happened no SES light.

 

He's never had any oil usage or burning problems with this motor.

 

When he moves the truck around in the driveway/garage (idle /slight throttle) he's says it runs so rough it is shaking the truck.

 

At least he has a SES light, so there should be code stored somewhere.  He said it goes in Thursday...

[NascarFan]

I'm having a similar problem with my '02 2500 HD 8.1 Allison w/ 5800 miles.  It just started.  I'm hoping it was just bad gas.  I filled from a station I had never used the day before my problem started.  I refilled a couple of days ago and it seems a little better.  I was searching this forum for a post I think I've seen before on the need for early spark plug replacement when I ran across your post.

[Shaners]

The dealer replaced a few more fuel injectors, and maybe a spark plug wire or two.  I think his engine is running better, but not as well as he thinks it should...

[Black02Silverado]

Where did it disapear to?

 

Sorry when I saw that post I couldn't help but ask.

[bcfitzsimons]

Your buddy should see if he has an intake vacuum leak at idle.  Mine had one, and (I think-and mind you, this is just my wild hypothesizing) when the stealer told me that I was sucking oil fumes into the intake (see past service bulletins), which caused a false rich mixture read from the O2 sensors, which then caused a lean-run condition, which then caused a knock, I decided to change out the plugs myself.  The dealer had to retorque the intake bolts to some new specs, but they kept the same intake gasket (!).

 

I tell you what-those spark plugs were BAD.  Carbon buildup everywhere, but worse on some than on others (so much for platinums!).  My 8.1 would vibrate when it idled (not too bad, though), and acted like it was missing when coming off the line.  The knock has nearly resolved with the intake nut retorque, new plugs, and 4 (that's right, 4) episodes of totally Seafoaming the block.  I think that there was just too much carbon buildup from oil fume burning.

 

It's easy to check the vacuum on these motors-just tell your buddy to attach a gauge to the nozzle on the intake that the fuel pressure regulator hose connects to.  It's underneath the engine cover, on the driver's side, next to the manifold pressure sensor (second cylinder from rear).  

 

HTH-Fitz