poss.egr problem

[bigblack]

Ok what I thought was a nice car has some issues.I just bought this 89 corvette(well traded my jeep for it)And am having some issues.I have another post for the no spark issue,but here is the one for maybe egr problem and maybe the answer to my bad pinging.With car not running I put a vacum pump on egr.It holds vacum fine.With car at idle Tried the same and it will not hold vacum no matter how many pumps i give it,and the car dont run any different.No change in idle at all.Is this normal on a 1989.I also noticed I have no vacum at the line to the egr at a idle or where at 2000 rpm.Is the egr solenoid bad?I checked timing,plug wires,plugs,cap,rotor,vacum leakes...But egr has me stumped.All I have is a cheap chiltons manual and it dont tell you much at all.Car runs great as long as you dont step on the gas(then it pings bad)And is getting like 23-24mpg on the hwy.

 

[topless82vette]

Isn't a tpi's egr normally closed type ( where vacum actually closes it rather then opens it) ? One way or another if the valve opens and no changes occur in how the engine runs egr passages are clogged. TPI is notorius for clogging right behind the throttle body in the plenum. Pull your throttle body off and spray some brake cleaner in the egr ports that should unplug it if there is carbon buildup.

 

[vetteoz]

I also noticed I have no vacum at the line to the egr at a idle or where at 2000 rpm.Is the egr solenoid bad?.

Have you vac on the input side of the EGR solenoid?
EGR only operates under certain conditions; recall car has to be moving above a certain speed / below a certain TPS % so you won't see it operate in the garage.

 

[bigblack]

Ok that makes alitle more sense.I was going nuts tonight checking it out.I have vacum to solenoid,but with it plugged in (wiring) and car at idle or any rpm I get no vacum to egr itself.When solenoid is unplugged I noticed that vacum travels through the solenoid but with power to solenoid it blocks vacum to egr side.I am still confused why egr hold vacum when car is off,but not while car is running.And why the hell the cars idle never changes while pumping vacum pump on egr while its running??Could egr port be plugged or I dont know???

 

[TedC]

L98 uses a negative pressure EGR. If you read up on these EGRs, they have two valves. ECM controls the primary valve via the solenoid. You can see the primary one using a mirror. Inside the EGR is a second valve that is controlled by back pressure (or the lack of). Make sure the EGR holds pressure at different temps. The springs age and then valves don't seal properly. If you manually hold up the primary valve, idle speed speed should be impacted. ECM does not send any EGR signals while in P or N.