Take a peek under the hood. The plugs are circular, perhaps 6mm diameter.

My former Accord was a 90EX and had the plugs.

good luck

 

Removed the 4 EGR port plugs by drilling, tapping and slide hammer.

The ports were not plugged solid but did have a fair amount of carbon build up. Removed the 5th plug and found a minimal amount of build up so I decided to not remove the 6th plug as this would require pulling the fuel rail and possibly disturbing 21 year old injectors.

Called the dealer and ordered the O-rings for FITV and IAC valves and also the fuel regulator O-ring. The port plugs are in stock.

Now 2 questions:

1.Do you guys install the port plugs dry or coat the edges with a sealant to help prevent a vacuum leak?

2.To help the car pass the NOx smog test, what octane fuel do you recommend? I heard that mid grade or premium is better because it burns cooler (less BTU's) than low grade and lowers the combustion temp which would help with the NOx reading.

Thanks.

 

1.Do you guys install the port plugs dry or coat the edges with a sealant to help prevent a vacuum leak?
Response: Dry, I re-used my old plugs and plugged holes w/ liquid steel epoxy. I read that new plugs are thin metal plugs. Lube won't hurt IMO.

2.To help the car pass the NOx smog test, what octane fuel do you recommend? I heard that mid grade or premium is better because it burns cooler (less BTU's) than low grade and lowers the combustion temp which would help with the NOx reading.
Response: I doubt it will help, but won't hurt. Higher octane does not burn cooler but ignites at higher temperture and burns w/ slower flame speed (my recollection).

good luck

 

Got the car back together last night and it seems to run a little smoother.
Only did a short 2 mile road test. Noticed that the vacuum gauge still only reads 2 to 3 inches of vacuum during acceleration while road testing.
I thought I read somewhere that more vacuum was required. Like up to 8".

Also as previously stated, I get no vacuum reading at the EGR supply hose (#16) when the car is in park and engine rpm is raised above 2000rpm, at normal operating temp. Is that normal?

So after I run the GTP treatment out of the current tank, I will refill with a mid grade or premium, then go in for my retest.

Hopefully the car will now pass the NOx test.

Any other advice on what to check?

Thanks.

 

The 8" vacuum is supplied by the Constant Vacuum Control (CVC) in the vacuum control box. Inspect the vacuum supply from throttle body to vacuum control box and vacuum line from control box to EGR valve for leaks. If no leaks, you may have a defectve CVC.

Yes, you should have voltage to the vacuum solenoid valve w/ fully warmed engine and idle speed.

You should download a 90-93 Accord Manual from Online Manuals links in DIY forum. I think there is a 91 Accord manual which should work for your 90 Accord. It has the diagnostic tree you need to perform.

good luck

 

Update on failed smog (High NOx numbers). Problem Solved.

On Friday 5/20, took the car in for the 1st retest. Car passed with very low numbers!

Here's the retest results.(compared to the original test).

15 mph NOx: 75ppm vs max limit of 559, Original test passed barely at 554. 15 mph HC: 20ppm vs max limit of 83, Original test passed at 7ppm.
15mph CO: .05 % vs max limit of .75, Original test passed at zero.

25mph NOx: 133ppm vs max limit of 516, Original test failed at 778ppm.
25mph HC: 10ppm vs max limit of 65, Original test passed at 6ppm.
25mph CO: .01 vs max limit of .63, Original test passed at zero.

Hard to say which changes I made resulted in the low numbers or which change had the most impact. Probably each of the changes lowered the to numbers to some degree.

Changes I made prior to retest:
1.Cleaned the EGR valve and EGR intake runners.
2. Set Ignition timing from 17 degrees to 14.
3. Ran a tank of G2P (Guarantee to Pass) treatment.
4. Used 89 octane vs 87 octane.
5. Ran car for 45 minutes before test. 1st test only 10-15 minutes.
6. Smog technician used two big cooling fans in front of radiator. 1st test used no fans.

Thanks to all of the experts who shared their experience. Much appreciated.

 

Good to hear and thanks for getting back. Too many times no one ever knows the end of the story. When that is really what helps everyone in the future......

 

Just wanted to give my thanks to the forum and share my similar experience.

Recently my 1990 Accord EX failed the (NO) portion of CA emissions test.

Had the EGR valve cleaned, no change. Had the EGR ports cleaned, BIG CHANGE!

Here are my NO (ppm) readings for smogs starting in 2005.

15 mph 178 797 656 673 179

25 mph 255 406 359 721 161

Year 2005 2007 2009 2011 2011/Clean EGR Ports

I ended up going to the Honda dealership to get the service done, because I didn't want to waste my energy trying to convince a mechanic to do something he's unfamiliar with, and that my 21 year old Catalytic converter and oxygen sensor aren't the problem!

Job: 2.5 hrs. (Other places may take longer)

Rate: $150/hr. (Quality=ouch!)

Word of warning: If you tell a mechanic to clean your EGR ports, they won't necessarily know the exact operation that needs to be performed. Be clear in telling them that the individual port plugs have to come out. They can't just scrape out junk from the side.

California uses pollution as a reason to get you to buy a new car, and trash the one you have. But how much pollution is created when making a new car?