All questions of "WHY", or "Just block it off" aside -- Texas
Dept. of Motor Vehicles makes the definitive requirement...

Does anyone know how to test the TBI EGR valve? I tried a
bench test vacuum application, with no results. The local
O'Reilly counterman (who has been right more often than not)
says that test doesn't work for these units -- even new ones
won't respond that way. And at $50+ per copy, its a little to
expensive to just replace.

thanks
ken koester

 

the EGR valve comes in 3 flavors, positive back pressure " P ", it needs some back pressure in the exhaust to work. negative back pressure " N ", it need to see a bit of vacuum in the exhaust to work. and one that doesn't care what the exhaust does. normally the different valves can be identified by either a " N " or a " P " on the end of the part number, the one that doesn't care won't have either a P or an N on it.

before you try this, you need to check to see if the EGR ports are open. with the motor at idle simply reach under the valve & lift up on the diaphragm, if there is little or no change in the motor your ports are clogged up & will need to be cleaned. a quick on car test i use to check the EGR valve is with the trans in park & with the motor at idle is to put direct vacuum to the valve & see if it opens, then do it again with the motor up around 2500 RPM. if the valve opens at idle & the EGR ports are clean, the motor will run very ruff or die, at 2500 you will hear a difference in the sound of the motor, normally it will drop by 100 RPM or more.

your O'Reilly counterman is kind of right, most people won't put their mouth on a dirty valve, but the positive & negative valves can be tested off the car, you must have a continuos good vacuum source hooked to it & either blow or suck on the port where the pintle is at.

bad EGR valves are common on all the TBI motors, i have replaced a ton of them. i also recommend to my customers they replace the EGR valve solenoid when ever i replace the valve.

 

Denn - I have an 88 TPI setup and I'm having EGR issues...you mentioned the Positive, Negative and Doesn't Matter EGR valves...None of my manuals indicate which I should have...can you tell me which or is there a link. I'm sure I'm not the only one woundering. Thanks.

 

Thanks for all the info my car's SES light just went on i flashed it, and a 32 came up, havent looked at the EGR yet but all the extra info going in will help