knocking or popping sound at start up

[dickgeorge]

Mostly when cold, if I have to stop in traffic right after starting, then tremendous hesitation. Sometimes 1-2 seconds before engine speeds up. Then hesitation at 2800 RPM and it lasts for a day. Overnight, restart and drive and about 5-10 miles later all is okay again until the next time. No codes and no pending codes. 2001 5 speed. New MAP, new air oil separator and rubber boot.

[edevlin]

"Every so often I get a popping sound from the exhaust when I start the car and accelerate. Almost like a hesitation. What I have to do is accelerate hard a couple of time and it goes away."


Mine does not really pop, but you can hear the exhaust gurggle, not when I accererate, but when I let off the gas. It does sound like unburnt fuel igniting, but just checked my mixture last week and its right on the money. I suspect it is just my exhaust system allowing you to hear more of what is going on. Anyone else with headers 100-cell cats and a high-flow muffler hear that sort of thing?

Ed

[Burg Boxster]

Originally Posted by edevlin

Mine does not really pop, but you can hear the exhaust gurggle, not when I accererate, but when I let off the gas. It does sound like unburnt fuel igniting, but just checked my mixture last week and its right on the money.

Ed-
I have a stock '99 w/ the 2.5 monster but had a similar gurgle sound when I let off . It went away when I replaced my AOS which I had a feeling was going bad. Not sure when/if you last inspected your AOS, but I'd pull the j-tube and also inspect your throttle body for more than a light misting of oil. Otherwise, you could be right and it might just be your headers.

[fatmike]

Originally Posted by edevlin

"Every so often I get a popping sound from the exhaust when I start the car and accelerate. Almost like a hesitation. What I have to do is accelerate hard a couple of time and it goes away."

Mine does not really pop, but you can hear the exhaust gurggle, not when I accererate, but when I let off the gas. It does sound like unburnt fuel igniting, but just checked my mixture last week and its right on the money.

Ed, my '02 S did this too. I checked the AOS, and it was fine. It kept getting worse until I ran a bottle of Techron thru... Amazingly easy fix, car runs like new now. Gas mileage dramatically improved too. My car is stock.

[NickCats]

Ok guys, what is the deal with Techron ?

Does this stuff really work, or is it snake oil ?

If it is worthwhile, where can I get it ( I don't see any Chevron stations listed in Illinois on their website ) ?

Thanks,

Nick

Originally Posted by NickCats

Ok guys, what is the deal with Techron ?

Does this stuff really work, or is it snake oil ?

If it is worthwhile, where can I get it ( I don't see any Chevron stations listed in Illinois on their website ) ?

Thanks,

Nick

Nick, I have used it. About once per year. You can buy at any of the better auto parts stores. It's a black bottle. They have it pre-measured for 12 gallons and 20. I use the big one. Cost about $11.

[HammerESQ]

Techron is good.. I've seen the results first hand tearing down a 911 motor that I ran Techron through with every oil change.

HOWEVER.. I have seen a more direct improvement in my Jeep and my 951 using the Lucas products. I highly recommend the Lucas fuel additive (http://lucasoil.hodgsoncorp.com/lucas_fuel_treatment.htm

It solved a bouncing idle issue in my Jeep, and marginally improved throttle response in the Boxster.