My 98 Chevy pick up with 5.7 knocks/pings under acceleration and when going up hill. It dosen't do it at idle or light acceleration. I've also noticed if it sits a couple days it has a strong fuel smell when I first start it, then goes away after the truck runs for a few minutes. The SES light has never came on. Any ideas? Thanks.

 

Have you tried a higher octane fuel? Sounds like a computer problem.

 

Yes, I've tried higher octane fuel. It don't seem to help any.

 

I took the truck to the dealership and they adjusted the timing. Now it doesn't ping as much but when it gets to opp. temp it will ping if you step in to it. Also when at opp. temp if you shut it off and start it back up, it will knock when it pops off. It also turns over slower.

 

Knock you say? What do your spark plugs look like? How many miles are on the engine? This is the 5.7L vortec with the plastic plenum, CPI/intake poppet valve system, correct?

Sounds like either 1, excessive carbon in the combustion chamber, leaky injectors poppets, or too high fuel pressure/rich fuel mixtures. Sounds like your SCPI (Sequential Central Port Injection) could be the culprit.

 

Yes, it's the 5.7 vortec. Haven't had a chance to check the plugs, the truck has 154,000 miles on it. If it sits for 2 or 3 days you can smell fuel when you first start it for about 30 seconds.

 

Well if you smell fuel, either it isn't getting burned in the combustion chamber, leaking externally, or it's running super rich.

I say check your spark plugs, engine vacuum and fuel pressure.

 

Sounds like its pre detonating from the pinging. Need to have a scanner hooked up and read real live data while its running. I bet that air/fuel mixture is way off. And it probably gets hot pretty fast too. Take them spark plugs off to see what color they are first.