So in the ongoing saga of chasing my miss I pulled the EGR valve today and inspected all the vacuum lines while I was doing the work. The EGR valve is fine, holds vacuum, operates cleanly, but the check valve just allowed me to pull air straight through it. I would have figured a check valve would check the airflow at least occasionally.
Since this is an EGR with an electrical solenoid on it as well, the check valve may be just a red herring, but I am just curious whether anyone knows what the thing should do in the first place.
Thanks for the input.
Take care and enjoy the ride,
Greg
__________________ If the only prayer you say in your life is thank you, that would suffice. Meister Eckhart
When you learn from your own mistakes, that's experience.
When you learn from the mistakes of others, that's wisdom.
When you fail to learn from any mistakes, that's government.
Continuing Saga,...................... Hi Greg, I have been following your saga for a while now & I can see you are dedicated to get to the bottom line. First the EGR operation, depending under what conditions you vac test,engine off,engine running cold,engine at normal operating temp will have different results. The most important factor you have to remember is the ECU controls all functions by monitoring inputs from CTS,MAP,MAF,closed throttle,part throttle,WOT etc. The ECU will only energize that EGR solenoid at part throttle for 3 reasons that I can remember, #1 if energized at idle it would almost stall the engine,#2 conbustion needs the cooling effect of cooler EGR gases recirculating to help stop "pinging". #3 when the ECU decides to test the EGR SYSTEM it does it by montoring the O2 sensors by looking for a lean drop below 50mv while it is commanding the test. If it sees the results it passes ,if it fails it may perform the test a few more times,still failing ,sets CEL........... SO, GREG, from your description of your checks what you should be zeroing in on is a EGR pintle that is 100% CLOSED NOT ALLOWING EGR gases to come into the intake manifold at idle causing that 1/2 miss (choppy idle) as I call it. The only way to confirm this is to remove EGR VALVE, then spray something like WD40 at the exhaust port of the valve & check for leaking at the pintle to housing seat. Slight seepage is normal because of capillary action of the solvent but if it is gushing down at the pintle & seat it will give a lean condition, unmetered air............ Greg, there is only one way to get to the bottom line of your saga, it's been my motto for over 40 years, " Repairs through testing ", you have to fix it with SMARTS NOT PARTS! Only then when your diagnosis proves to you that you have a malfuncting part. If you want to go down this road, I'm with you, we can't leave one stone unturned going down the diagnostic road to success ! ------ Ray
Additional Info,--------- quote; "check valve is allowing to push air right though it". Greg----- Normally when the solenoid is not energized by the ECU as when the engine is off the solenoid will be in a relaxed open position, when the ignition is turned to #2 current is sent to the positive side of the solenoid through a protection fuse that protects emissions solenoids, at the same time the ecu is sending a ground circuit locking that solenoid CLOSED until it determines when to enable EGR operation. So when engine is started there is no vac flow through the solenoid to the EGR valve. When EGR operation is needed determined by the ECU,very simply it takes the ground circuit away ,the solenoid unlocks & vac flows for EGR operation. The theory behind this type of solenoid operation is that the windings in the solenoid run cooler because there is only current flow from key on during open loop time,very soon after closed loop the ECU will determine when to energize EGR. Easy example ----- cold engine start up verses 300 mile road trip time ! Those solenoids are going to last a lot longer with more time off than on. Hope this answers your question.---- Ray
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