This one has got me stumped. I have been running my car with the vacuum line to the EGR plugged off for a few months. The car would stumble at cruising speeds with the EGR connected. When the EGR is plugged off it runs fine. A couple months ago I installed a new EGR vacuum solenoid. That didnt help. So finally I got around to buying a new EGR valve and installed it . That didnt help. So I plugged that one off and it runs fine.
My oxygen sensor probably has never been changed and its at 84k miles. I have bought a new one , but I have to get the old one heated with a torch to get it out .
My question is , does the o2 sensor control how much vacuum the EGR should draw. That my explain why the egr isnt working properly.

Thanx in advance.

Len

 

I would check every hose you have under your hood.
You will probabaly find the problems.
ESPECIALLY THE UNDERSIDE!
You are on right path

 

Thanx KED ,
But I guess Ill run this by the engine tech board and see what develops.

 

EGR only gets activated when the car's warmed up, at a high road speed, and the engine is at a low rpm. I think Karl's along the right track; I wonder if your EGR solenoid is somehow stuck open, and allowing a constant vacuum to your EGR. Follow the egr vac line as it goes from the EGR, into the vac solenoid. The other line exiting the vac solenoid is the vacuum "source". Try following that line backwards, and plugging it off. Then you'll eliminate the EGR solenoid.

 

Thanx TomP ,
If I block the solenoid off wont that also eliminate the EGR valve.

Also the car is messing up at highway speeds and warm. Its almost like it is pulling too much vacuum away from the engine.

It feels like at highway speeds that the engine is hesitating , like its leaning out too much. The cars idle is sometimes mildly eratic almost as if it has a performance cam , but it never stalls. The acceleration is sluggish with the EGR connected.

With the EGR disconnected it runs great except for the mildly eratic idle.
My EGR solenoid runs off of a box that looks almost like a MAP sensor . It has a 4 wire plug and 2 run to the EGR solenoid. I assume that box tells the solenoid when to open and close.

Does the 2.8l camaro/firebird engine have a higher performance cam than the basic 2.8l.
If it does than that might expain to me why the idle isnt as smooth as my 3.1 Lumina.

 

ALL MPFI
1985-1992 60* V-6
have the same cam.
ALL MPFI
NOT TBI as in S-10 Blazer, tho!
I had that happen, egr caused the SES light to come on then go off.
Turned out it was a cracked housing EGR hose on the bottom side, by exhaust manifold.
Problem solved for free (found new proper sized hose in spare stuff).
Only takes a look.
You are describing classic bad worn vacuum hose problems.

 

Yeah Ked ,
I think youve put me on the right course. I finally got a chance to look under the intake at the back of the engine , there is a 3 line fitting under there. One line doesnt look too sporty . I'm going to take a better look at it tomorrow night .
Thanks for the help and TomP too.
Ill keep you guys posted.
Thanks Again.

 

Plastic breaks easy.
Use 5/16" windshield wiper hose to patch cracks.
Even after my 3.4 swap, I had to remove the upper intake to cure a few stray bad/worn hoses.
Happy hunting!