EGR system
 

I believe EGR system was added after 93 model year LT5.
I always thought EGR came into play after cold start and its purpose was to aid in faster warm up in order to control emissions.

A few minutes I was talking to a local mechanic regarding light detonation at light throttle and he was saying that it may be due to clogged EGR valve.

Does EGR come into play after motor has been fully warmed up?

Your thoughts?

Re: EGR system
 

EGR was added in 93. It was planned for the earlier models but was not included, hence the boss on the side of the plenum.

What you are thinking of is the air injection system which helps push air in to the exhaust system to help the cats get up to temp quicker.

EGR only functions while at a cruise.

Re: EGR system
 

Hey Jeff,
Do you know under what specific conditions the EGR valve opens and closes?
Does it operate either fully open or fully closed or is it proportional?

Re: EGR system
 

That was my next question.

Re: EGR system
 

I suspect he is referring to a malfunctioning EGR valve. In which case the operating parameters for it are not that relevant. If the valve won't close properly, you can have driveability issues. I don't know that detonation is one of those issues, though.

I don't know how prone the LT5 system is to that, nor how easy it is to check or clean the valve, etc, since my car does not have EGR.

Do you get detonation at light throttle?

FYI, as Jeff mentioned, the AIR pump warms the cats up faster. EGR I believe is to prevent excessive NOx emissions by cooling down the combustion chamber

Re: EGR system
 

I am getting mild ping when fully warmed up, 2000 to 3000 rpm, moderate acceleration.
One suggestion was to drive the hell out of the car (to 7000).

I was thinking of running BG K44. Should besafe, right?

Re: EGR system
 

Quit running that cheap 87 and step up to some 93 :p

Re: EGR system
 

Ha, ha. Very funny!
I use to run Sunoco 94 'till they droped it about 5 years ago. Since then, either Exxon or BP (Amoco) 93 - Mostly Exxon.

Re: EGR system
 

are you talking about tip in knock or does this happen with no throttle changes?

Re: EGR system
 

At tip-in. Starts right around 2000 to 2200, sometimes continuing to around 2600 to 2800.
This only occurs with slight acceleration and goes away if I push the throttle more aggressively.