Carbon

[gp90se]

..... and even diesling

 

We went over this in another threat, an EFI car cant have run on because no more fuel gets pumped into the motor.

 

 

Check a couple things first, have someone start the car while its cold with you under the hood and ya hands near the manifold/downpipe, check for leaks there

 

That diesel sounding motor is prolly from not being allowed 2 warm up earler in life in the cold. my buick does it, not as bad and it's starting to bother me, but as long as ya let it warm up before driving it, I don't think you will cause anymore damage.

[Prospeeder]

Oh, i was just saying what carbon knock is or can be, WHen the carbon turns red hot and ignites the fuel, i didnt say just in W bodies or anything, just in general, that could be a carbed vehicle too, but yea, EFI cars cant diesel

[GP1138]

Very normal, they ALL do it, just how they were manufactured, it dosnt hurt anything, the reason if you didnt guess, is because when its heated up all the way, the metal expands a bit and makes a tight fit, while when cold it doesnt and the piston slops around in the cylinder, thats my take on it from my Auto teacher, (GM tech for 20 years) he says GM assured everyone it was completly normal and wont have negitive effects

 

Mine said it was because GM put the piston wrist pins in the center of the piston instead of slightly off center, resulting in better gas mileage, but the loss of the slap deadening due to the piston sliding against the cylinder wall, which was what the off-center pin was designed to do.

[Prospeeder]

Really, Hmm, mabye the 3100 and 3400 were different or somthing, It may be a combo of the 2, the skirts being to small and the wrist pins being off center

[GP1138]

Really, Hmm, mabye the 3100 and 3400 were different or somthing, It may be a combo of the 2, the skirts being to small and the wrist pins being off center

 

Thing is, they're on center now, causing the pistons (when cold and not expanded like when warm) to bounce off the sides of the cylinder walls, causing the slap sound when cold. Older engines (Gen II?? I can't remember exactly when they did it) were off-center, causing a tiny hit in gas mileage but no slap during warmup due to the piston being flush with one side of the cylinder.