1991 GTA - has a tip in stumble and chuggle in low-rpm/high-gear, cruise BLMs of 108. I went through all the test on everything to no avail. Even the EGR tested well according to the service manual. On a hunch, I pulled the vacuum to the EGR and plugged the hose so there was no vacuum leak. All my problems were solved.

EGR duty cycle is going to 99% as soon as I touch the throttle. I think that is normal. But, since it's a negative backpressure design, I wonder if the vacuum bleed off isn't working well. The manual says to apply vacuum to the EGR valve and start the engine - the vacuum should drop and the valve should close. Well, it does, but not instantly. So, maybe the backpressure bleed-off diaphram isn't working well?

Or, maybe the exhaust gas is somehow too rich and the slightest EGR bogs the engine?

Any ideas before I pull the plenum and throw on a new EGR? BTW, I took out most of the EGR wall in the plenum and the exhaust is catless with a flowmaster.

 

TTT

 

try again