egr solenoid

[GravyDavey]

If you do, I'll buy one from you.

[Saudade]

Admittedly, I'm not sure under what conditions the ECU commands the solenoid to energize. As noted above, when energized, no vacuum is drawn from the egr valve which keeps it closed.

So just for fun, I warmed up my '88 and blipped the throttle while watching the egr. I could see the egr pintle move in response to throttle input. Then raised and held (around 2500) and saw the pintle fully open, then close as the exh backpressure equalized. Can't say if it completely closed. Repeated this a few times. Then unplugged the solenoid and did the blips again. I could not see any real difference.

Your high CO is due to a rich condition. Check your sensors, make sure your TPS is adjusted correctly and your air filter is clean. Go back to Cruiser's site for the details.
Most common cause for rich is a bad O2 sensor.

Once you correct the CO levels, your NOx will rise a bit. The rich condition cools the exh a bit and can lower your NOx levels. Once you clear this, exh temps may rise and increase NOx but the working EGR will keep them in check.

[GravyDavey]

Yeah, I've been chasing a rich condition for a while. Got a smoke tester last week and found 4 vacuum leaks. Fixed 2 of the leaks (MAP TB port and MAT sensor). Unfortunately, 2 of the leaks are from the emissions equipment, temp sensor in the airbox and egr pintle. I'll bypass that temp sensor all together once it passes smog. I just have it connected to pass the visual inspection. Propped open the airbox blend door and it comes up to temp within 10 minutes. Holds tight at 195 pretty much. Sensors all seem to test fine.

[Saudade]

The "sensor" in the airbox controls the servo at the front of the airbox. When cold, it allows vacuum to close the servo and pulls air in from the hose connected to the exhaust manifold. Once warm, it blocks vacuum and the servo opens to alliow fresh air in from the front of the airbox.

Mine went bad. Rather than replace it I popped the vacuum line off (from the vacuum harness and wrapped a small piece of electric tape around it and put the hose back on. Vacuum leak solved. It also looks "untampered". Just FYI, I took the hose to the exh manifold off one year and failed due to a "tampered" system.

If you want to replace it, here's the part on eBay.

https://www.ebay.com/itm/183821281714

[cruiser54]

I have 6 solenoids, 4 transducers, and 2 EGR valves.

If we could shut off that round opening/port of the EGR at the manifold, everything else would look just fine.

[GravyDavey]

"Once you correct the CO levels, your NOx will rise a bit. The rich condition cools the exh a bit and can lower your NOx levels. Once you clear this, exh temps may rise and increase NOx but the working EGR will keep them in check."

You were spot on here. NOx went up quite a bit on the 2nd test. The only thing I changed though was to put on a new cat.

[Saudade]

So you passed?

[GravyDavey]

Yes, no problem with the new cat. It was really close with the old one. These aftermarket cats don't seem to last too long. I passed twice with the old cat which was a Walker.

[Saudade]

Nice. Too bad those dang CARB cats are so expensive. Last one I put on was a Walker back in 2014. Had some issues with other components over the next few smogs, but passed no problem this past May.

Good for 2 years!!

[GravyDavey]

Well, I now have a low vacuum reading. Floating a bit. I'll start a new thread on this because it's not related to the EGR.

[cruiser54]

Davey, have you ever removed the EGR valve and verified that it is closing completely?

[GravyDavey]

It was definitely leaking vacuum from the pintle. After I passed smog, I removed the EGR completely and capped the opening using a egr gasket and piece of steel plate. That was my last known vacuum leak. I haven't had a chance to put the smoke machine back on it to make sure my EGR delete job was good.

I haven't messed with the EGR since I took it off. I was thinking about cleaning it, but when I saw that it would be pretty easy to delete it. I went that way.

[Saudade]

Well, you're good for 2 years. save it for next time.

In the meantime, you can pop the lid off the transducer and check the diaphragm. Just make note of which way it goes on. You can check the egr itself with the smoke machine of with a handheld vacuum pump.

[GravyDavey]

Cool. What am I looking for when I open up the transducer? Torn diaphragm? Something else?

[Saudade]

A torn or worn out diaphragm and any cracks in the tubes where the hoses connect. Make sure those short hoses are good too. The diaphragm is pushed by the spring which allows vacuum from the solenoid to vent (low backpressure). When enough back pressure from the exhaust is present, it pushes the diaphragm upwards to close the hole (high backpressure). This allows vacuum to the egr valve. That vacuum then pulls the pintle off it's seat and bleeds exhaust back into the intake.





Sadly, the transducer doesn't seem to be available as a separate part as it comes with the EGR. However I have seen some similar on other EGRs. Don't know if they would work.