Testing EGR while car is running

[Q45dude]

While the car is running, if any of the vaccum hoses from the EGR are pulled and there is no change does that mean the EGR is not functioning properly??

thanks

[Infinitiguy19]

Read this: http://www.nicoclub.com/FSM/Q45/1994_Q45/

[Q45tech]

The exhaust system doesn't have enough back pressure at idle to properly flow enough exhaust gases back into plenum..... but some occurs.

However manually pushing the EGR master valve upward can disrupt the idle because the ecu doesn't expect the extra oxygen poor air and may stumble or die..............why egr is blocked until 1400 rpm and until coolant temp is warmed up above 150F.

Pushing the master valve up is a good easy idle test for exhaust to plenum flow blockage but it doesn't tell the whole truth just shows part of system is working.

[Q451990]

I agree with PPastos in terms of reading your FSM, but to answer your qestion - no.

The test is to rev the car while feeling the bottom of the valve. You should feel it lift and flutter between a certain RPM range. Something like 1500 and 3000 RPM I think.... the FSM will tell you the exact range. You also want to push the valve fully open from the bottom while the car is at idle to see if the engine chokes down or almost chokes down. If it doesn't the port in the plenum is probably clogged.

Heath

[Q45tech]

The technically correct method is to monitor MAF voltage under cruise steady load and view the grams per second mass air flow drop by 5-10% when egr valve opens.......................this might only be a change of 1.8 dropping to 1.7 volts at 55 mph on a level roadway.

The air flow drops by 10% because the egr reuses the 10% over and over and over to reduce the combustion temperature.