CorvetteMike2024

Hello all,

I have failed my California smog test. Hi Nox readings at 15 and twenty five. Egr valve is not stuck. I think my EGR solenoid my be suspect. Any way to test solenoid? I also want to clean the egr passages. Anyone have any tips on cleaning the egr passages?
No check engine light.

Thank you for your replies

My vette is an 89

ex-x-fire

Tee up a vacuum gauge between the solenoid & valve, take the car for a drive. You should get a vacuum reading just above idle (may not work without the car driving) through to high rpms.
You could also put a vacuum pump on the egr, start up the engine, and apply vacuum. The engine should stall or run very rough.

topfuel67

How is your engine temp? On my 93 jeep I eliminated the engine fan and put a cheap electric fan. It couldn't keep the engine cool enough for the smog test. I put the engine fan back and it lowered the temp and nox.
I put the hypertech chip in my 89 and it runs considerably cooler.

CorvetteMike2024

I have both my fans on manual switches. It was running about 180 to 200 during the testing. I found a egr vacuum solenoid at Ecklers. EGR valve is working. Im going to yank the plenum off and make sure all the passages are clear in the plenum and intake manifold. Thank you for your replies.

ctmccloskey

I had the same problems with a 1988 C4 Coupe that I own. On my car the EGR system failed because the vacuum solenoid was not working properly. After removing the EGR I found a ton of carbon down in the passageways. I ended up removing the upper intake system to get access to the parts better.
The EGR valve I had would still move but not make the engine run rough upon application of vacuum. I ended up replacing the EGR, EGR Vacuum solenoid, Fuel pressure regulator, injectors, EGR Temp sensor and cold start injector and several feet of vacuum line.

The Carbon is hard and it can be removed or softened with carburetor cleaner. Then a set of Gun cleaning brushes would be real handy to snake out the passageways. I ended up using a Sand Blasting cabinet to blast out the remaining carbon, it was a real PIA..... The high pressure sand really cleaned the passages out and down to bare aluminum.

Check your Temp sensor in the EGR system, mine had failed as well so I heated up the parts with a torch and then soaked it in KROIL oil, it came right out. On my car before the emissions test (where I failed for High NOX) the temperature sensor was unusually hot and would start the protective covering to burn a bit. This might be an indicator that the EGR is not working properly.

I hope that you find a way to get the emissions back where they belong without spending a bunch!
Good Luck

CorvetteMike2024

Replaced the egr valve , egr solenoid, and egr temp sensor. Put a new cat on. Still failed emissions due to high NOX. Ran a scan on my vette today. Its going into closed loop. Rich Lean flag goes rich/ lean. Cross counts 171, Block learn 151. The engine runs good. Still haven't checked plugs. EGR duty cycle is working. Seems like I have weak vacuum though. Any suggestions?

JackDidley

Its been a long time since I datalogged but block learn should be 128 + or - 8. Something is causing a lean condition. Timing is not advanced is it ?

383vett

Maybe you have a slightly fouled plug or two. Might want to pull them.

mtwoolford

I've seen it happen; if those passages are blocked, nothing in the EGR system is gonna work

auburn2

Could it be a bad catalytic converter?

CorvetteMike2024

EGR passages are all clear. I removed the plenum and cleaned out the passages. They were all clear. Timing is spot on a 6 BTC. Seems like I'm not getting much vacuum off the throttle body port.

CorvetteMike2024

My car has always run lean. I haven't been able to richen it up.

CorvetteMike2024

I don't think my egr is opening up. I'm still failing emissions. Does my ecm control the egr? Running a scan does not show any opening egr signals. No codes. Any ideas?

vermatrix

Wow, I almost forgot about that Smog Check thing. That is one thing great about living here in Wisconsin, NO SMOG / SAFETY or ANY checks of any kind on your car. There are guys running around with really beefed up 383 stroker vettes and as long as they dont run straight pipes or cutouts, no one cares. Of course the bad part is having to store the car for 6 months of the year.

RetroGuy

It would be nice to live in a world where everyone was onboard with keeping our air clean/cleaner. I'm fairly certain the exhaust from older Wisconsin vehicles travels to California and settles in to enjoy our mild weather.

vermatrix

Well for one, prevailing winds are east not west. So you are getting more pollution from Japan and China then Wisconsin. Also, anything in the air that hits that Pea Soup in the LA Valley is instantly atomized into toxic waste. The whole CARB thing is more about established bureaucracy and state government overreach then it is about protecting the air. Its philosophy is based on pollution levels from cars made in the 60s and 70s. Your high performance cars pollute very little compared to then. Most of the muscle cars around here are clean burning, smokers are pulled over. Sorry if I made it seem like Cheech and Chong mobiles were running loose everywhere. Clean air is something we enjoy here and law enforcement definitely protects.

John A. Marker

What kind of exhaust system/mufflers do you have? On my 95, the exhaust was reworked by the PO and it only had Magnaflow mufflers. I pulled the O2 sensor and measured the back pressure. I had zero back pressure. This resulted in the EGR valve not working properly. I ended up putting temporary restrictions in the exhaust pipes to increase the back pressure. It then passed SMOG. You might check this as a possibility.

CorvetteMike2024

Stock exhaust with 2 pre cats and the big one.

xrav22

Make sure your balancer has not spun, so your timing will be actual. Mine had a crappy factory balancer on it.
keep plug wires from crossing, sparkplug gap changed in 85 per recall. I forget which way the gap went. Change the oil.
good luck

mtwoolford

If you fail a CA smog test, first things first, ignition tune up, plugs, plug wires, rotor, rotor cap. Once all that's known to be good, you can start chasing other things.