• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

CA SMOG FAIL: High HC @ Idle Only

Egr flow too high?

Sounds less important for now. I wonder if I start with vacuum valve or the actual egr valve???
Stuck open EGR valve will cause poor idle, it could be related to your other running issues too. IDK the strategies 2.4 uses to monitor EGR flow other than the EGR temp sensor, but modern cars use MAF data and other sensors to make the calculation.
I would check the EGR first, but you can also unhook the sensor, see what the resistance is on it. Seen a few that had the wiring break on them or the sensor fail, when the valve was fine. Just beware, if it's the sensor, there's 2 different sensors, resistance is opposite directions...NTC or PTC.
yay, EGR identification riddles. For clarity...

Valve is the dohicky on the strut tower that has two vacuum lines, or is it the dohicky that lives under intake where two pipes merge?
Now I have to ask this question, which I didn't get a confident answer on in another post, a while back.f

Could this fault be the cause of having the vacuum lines backwards on the EGR solenoid (strut tower dohicky)? I'm not 100% certain which nipple is supposed to go to intake, and which is to go to valve...or if it matters any at all
Maybe... The solenoid applies vacuum to the EGR valve.

Apply 12v and ground to the solenoid and see if the engine stalls. Swap the hoses around and recheck.

Bad EGR sensor would throw a sensor code.

Bypass the solenoid, apply vacuum directly to the EGR valve. (Use engine vac, hand pump, or even a vac hose in your mouth) Engine should stumble. But yours says EGR flow is too much, so .. BLOCK OFF EGR to the intake manifold and that code should go away and idle should be better IF it's a true code.
Last edited:
I’m going to drive it to The Bay for the weekend. Maybe I can find a spare EGR in the nor cal junkyards…will also test when I return
If you wanna get fancy, you can monitor the EGR temp sensor voltage (connected) or put the meter on the two terminals (disconnected) and monitor the resistance changes with EGR flow. We have scan tools for that on OBD2 cars.

I've never had an excessive flow code on a brick. I've only had a temp sensor code be tough to fix because all the JY parts were bad too.

A stuck open valve is possible in your scenario. Apply and remove Vac to the valve and you should see the shaft moving in and out. (Credit to another Bricker for mentioning that test in another thread)
Thanks Zvolv for so much good insight.

I think the plan today is to just send it! Skip the yard parts, because I agree, they're all SUS!

When I get back, I'll dive into testing. I suppose it's not a big deal to just order a new EGR and move on. I was lucky in 2017 and found a EGR for the Miata in the Fairfield yard. Never had that riddle again.

It was a similar stumble at idle...mostly when car was warm, then I'd have hot start issue. The Volvo is pretty much acting the same. I'd love a factory diagram of the EGR vacuum connections, just to officially rule that variable out.
No problem, Myles. I appreciate a Thank You.

All the EGR valves I found had ports that were clogged with rust, but the pintle would still open and close properly.

I broke an EGR pipe once and I just cut a piece of a beer can out and slid it under the pipe at the intake to stop the air leak. You could just do the same and the EXCESSIVE flow code should no longer be present.
I've had the excessive flow code before, came from an open wire on the sensor.

The vacuum to/from the solenoid on the strut tower may be an issue if not plumbed right. Been ages since I saw it, seems like there's an in/out/vent setup. Getting those swapped around can cause some issues, should be a vacuum diagram including what lines go where on the solenoid...should be on the pass. strut tower.

For checking the valve, easy enough to supply vacuum to the valve itself, see what happens. Also, if you've got a high flow when it's cold, grab onto the pipe where it attaches to the intake. If it's stone cold like the intake but you have a high flow code, chances are wiring or sensor. I grabbed a few valves when I was fighting the intermittent code on mine, only to find a broken wire. Insulation was intact, wire wasn't, so no visible issue until I did the old Ford 'wire wiggle test' with an ohmmeter on the sensor connector. Should be around 600 ohms cold if memory serves, but it's been a while.
Mine was throwing an EGR temp sensor code. I forget the readings, but it took a few "in spec cold" sensors to get the CEL to go away.
So I put about 1,200 miles on the car last weekend. It was a road trip from Lost Wages to The City by The Bay....and back. No misfires or other engine management related concerns. The EGR related leak is still persistant, so it doesn't idle reliably.

Y'all got me thinking about EGR valve riddles, and my uncertainty in getting the correct one. There are two LH2.4 era cars in my local yard. One is a 240 and the other a 940, both NA. Should/Would/Could those have the same EGR valve I need? Debating grabbing them to test, as a new replacement isn't the easiest thing to source.