and you didn’t ask me this yesterday… duuuurrrr i can check bullitens on that thing retard
maybe this
#PIP3081: SES Light and P0300 When Towing , Cruising Uphill or on Hard Acceleration - kw 4.3 5.0 5.7 accelerate cruise cylinderhead DTC L30 L31 L35 LF6 LU3 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 - (Jul 23, 2004)
Subject: SES Light and P0300 when Towing, Cruising Uphill or on Hard Acceleration
The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Condition/Concern:
The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3,4,5 or 6 will be the ones to experience this.
Recommendation/Instructions:
If the P0300 SI diagnostics did not isolate a concern, the following may help:
Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance:
• Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide.
• Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone.
Reassemble the cylinder heads using new valve seals.
.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
Models:
(96 - 02 Chevrolet Astro) and (96 - 02 GMC Safari) and (96 - 00 Old Body Style Chevrolet Suburban) and (96 - 00 Old Body Style Chevrolet Tahoe) and (96 - 02 Chevrolet Express) and (96 - 00 GMC Yukon) and (96 - 00 Chevrolet Old Body Style C/K Truck) and (96 - 00 GMC Old Body Style C/K Truck) and (96 -02 GMC Savana) and (96 - 99 P32 Cab and Chassis) and (96 - 02 Chevrolet S-10) and (99 - 02 Chevrolet Silverado with 4.3L V-6 Engines (96 - 02 GMC Sonoma) and (96 - 02 GMC Sierra with 4.3L V-6 Engines)
OR
#PIP3470A: Light Throttle Chuggle Hesitation And/Or Misfire - Possible Reversed Injector Nozzles - (Feb 9, 2009)
Subject: Light Throttle Chuggle, Hesitation, and/or Misfire - Possible Reversed Injector Nozzles
Models: 1996-2000 Chevrolet Astro, Blazer, C/K Pickup, Express, S10, Silverado, Suburban, Tahoe
1996-2000 GMC C/K Pickup, Jimmy, Safari, Savana, Sierra, Sonoma, Suburban, Yukon
with 4.3L
This PI was superseded to suggest using the Tech 2 cylinder balance test to isolate reversed fuel injector nozzles. Please discard PIP3470.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may complain of an engine misfire, buck, chuggle, or fishbite feeling at operating temperature. Typically, this concern occurs on deceleration, shortly after cresting a hill, or shortly after TCC engagement. In some cases, the customer may complain of poor idle quality as well. If questioned, the customer should advise that this did not occur until recent engine repairs that required R and R of the fuel injector metering block.
The intensity of this condition can vary from a light bump to a severe buck, which may also induce a driveline clunk or propshaft ringing noise that can be mis-interpreted as a transmission or driveline concern.
Upon inspection, all Tech 2 data is generally normal with the exception of some random misfires that occur during the concern. This condition feels similar to a chuggle concern that is caused by incorrect CMP retard but it normally feels a bit more pronounced.
Recommendation/Instructions:
If SI diagnosis does not isolate the cause of this concern, CMP retard is adjusted correctly, and this did not occur until recent engine repairs were performed, monitor the Misfire Data List while performing a Tech 2 Cylinder Balance Test. Whenever a fuel injector is turned off, the related cylinder should count misfires on the Tech 2. If an incorrect cylinder counts misfires when a specific fuel injector is turned off with the Tech 2, this concern is most likely due to reversed fuel injector nozzles.
If the Tech 2 will not allow you to perform this test for some reason, or if it has isolated reversed fuel injector nozzles, remove the upper intake plenum and compare the location of each fuel injector nozzle to the cylinder identification numbers that are molded into the Fuel Injector Metering Block.
If any of the nozzle locations do not match the identification numbers, remove the nozzles, install them in the correct location, and re-evaluate the concern.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
OR
maybe it’s a TCC shudder
Inspect the following components in order to avoid misdiagnosis of the TCC shudder and possibly disassembling a transmission and/or replacing a torque converter unnecessarily:
• Spark plugs--Inspect for cracks, high resistance or broken insulator.
• Plug wires--Look in each end. If there is a red dust (ozone) or a black substance (carbon) present, then the wires are bad. Also look for a white discoloration of the wire indicating arcing during hard acceleration.
• Distributor cap and rotor - Look for broken or uncrimped parts.
• Coil--Look for black on bottom indication arching while engine is misfiring.
• Fuel injector--Filter may be plugged.
• Vacuum leak--Engine won't get correct amount of fuel and may run rick or lean, depending on where the leak is located.
• EGR valve--Valve may let in too much unburnable exhaust has causes engine to run lean.
• MAP/MAF sensor--Like the vacuum leak, the engine won't get the correct amount of fuel for proper engine operation.
• Carbon on intake valves--Restricts proper flow or air/fuel mixture into cylinders.
• Flat cam--Valves don't open enough to let proper fuel/air mixture into cylinders.
• Oxygen sensor--May command engine too rich or too lean for too long.
• Fuel pressure--May be too low.
• Engine mounts--Vibration of mounts can be multiplied by TCC engagement.
• Axle joints--Check for vibration.
• TPS--TCC apply and release depends on TPS in many engines. IF TPS is out of specification, TCC may remain applied during the initial engine crowd.
• Cylinder balance--Bad piston rings or valves that seal poorly can cause low power in a cylinder.
• Fuel contamination--Causes poor engine performance.