Slap ShotI have a question about piston slap. I know this is a GM engine issue. They like to make pistons with no skirts. I'm thinking about buying a '99 with 52,000 miles and it has a pronounced piston-slap noise when the engine is cold. I know GM has TSBs on this issue. If I purchase this Corvette with piston slap, will I have to plan on replacing the pistons or will it be OK to drive for another 50,000 miles?Via E-Mail
There is a Technical Service Bulletin out, but it starts with the '01 model year and involves a possible cut or split in the O-ring that seals the oil pump to the pickup tube. It pertains to not only the C5 Corvettes, but all LS1-based engines in all other cars and trucks. The bulletin number is 02-06-01-238. This may or may not be the cause of the knocking noise. Several repairs were attempted with new and redesigned pistons, and we even tried some tight piston-to-cylinder-wall clearances. We had some immediate success, but the noise usually came back after 1,000 or so miles.
A coating on the piston skirts helps suppress some of the noise. Whether or not it will last another 50,000 miles is debatable, but as long as it doesn't get worse over time, I'd guess it would last the lifetime of the engine. I once had a 3.1L Euro Lumina that showed 136,000 miles on the odometer when I sold it, and it had some of the worst piston noise (when cold) for the 90,000 miles I owned it. The noise quit after the car warmed up. It all comes down to what you can tolerate, and most C5 owners will not tolerate much in the way of piston noise.
Lock And KeyI have a '99 Corvette and it has a salvage title. I made repairs and put 2,500 miles on it this past summer. About a month ago, the steering Service Column-Lock came on. It says to pull the key and wait 10 seconds. I've done this too many times to count. The car shuts off at 2 mph. I can start it up and idle all day, but to move it is a pain. Is there anything you can tell me to repair for the spring of 2004?Terry Garwell
The notorious column-lock issues have been covered several times in this column. Shutting off is part of it, as the theft-deterrent system lets the car run, but not move. Usually, removing the key and waiting 10 seconds is a short-term fix, but you need one of the repairs.
There are two Chevrolet items on this: one is Bulletin No. 01-02-35-008, which according to the coverage does not include the '99; the other is Technical Campaign No. 01044A, which does cover '99 for customer satisfaction. Your VIN will determine which item applies to your car. Since your C5 is a '99, the bulletin repair (if covered) would require you to pay, while the customer satisfaction campaign is a freebie. I'm not sure why there are two different items, but hopefully you're in the freebie area.
Revvin' Without A CauseI own an '02 LS1 coupe and have completed several performance upgrades, but I've run across a problem. My upgrades include the following engine-specific changes: a 160-degree thermostat, a Pro-Torque converter, Nology wires and Beru plugs, a throttle-body bypass kit, a Twin Flow air-intake system, a high-performance MAF, an underdrive pulley system, a West Coast Corvette (WCC) modified throttle body, and a custom computer to align it all; a shift point change and rpm adjustment was also included.
When the car starts up, it revs up to about 2,500 rpm and works its way down to idle in about 5 seconds. Once the engine is warmed up, it doesn't happen again unless the engine is shut off for several hours. Should I be concerned about the high rev? WCC has told me it's because of the throttle body and nothing can be done about it. I'm looking for a second opinion.Matt Blackman