88grandmarq
04-19-2005, 08:15 PM
I found this posted on corral.net. So, if you got a EGR code (31,32,33,34 or 35) and have crappy MPG, this might explain why.
This also applies to all you guys who think blocking off the EGR "improves" performance.
Quote:
"you shouldn't run the block-off unless you're either not running EGR or there's an alternate supply for it, because...
...the fuel management strategy assumes the presence of a functioning EGR system and you'll get an overly lean part-throttle cruise if you block it off and don't have a chip tune to tell the computer not to...and when you have a lean part-throttle cruise, the EEC picks that information up from the O2 sensors and adds fuel. But it doesn't just add fuel to part-throttle cruise operation, it adds compensating fuel even during open-loop (non-O2-feedback) conditions such as startup, idle, and WOT.
Short story is since the EEC assumes a functioning EGR, and if you haven't instructed it otherwise, you're setting yourself up for rich running and resulting performance/driveability issues by blocking off its flow."
This also applies to all you guys who think blocking off the EGR "improves" performance.
Quote:
"you shouldn't run the block-off unless you're either not running EGR or there's an alternate supply for it, because...
...the fuel management strategy assumes the presence of a functioning EGR system and you'll get an overly lean part-throttle cruise if you block it off and don't have a chip tune to tell the computer not to...and when you have a lean part-throttle cruise, the EEC picks that information up from the O2 sensors and adds fuel. But it doesn't just add fuel to part-throttle cruise operation, it adds compensating fuel even during open-loop (non-O2-feedback) conditions such as startup, idle, and WOT.
Short story is since the EEC assumes a functioning EGR, and if you haven't instructed it otherwise, you're setting yourself up for rich running and resulting performance/driveability issues by blocking off its flow."