Failed Smog test

[michigan_accord]

So the 88 accord failed 2 days ago. It failed its first test about 2 weeks ago for bad idle and timing, but emmissions were fine. After I fixed the idle and timing however, the NOx shot through the roof and it failed as a gross polluter at the 25mph test.

I am trying to figure out what caused this. Abviously advancing the timing (it was retarded too much for the first test) didnt help, but it seems like a huge jump.

The tech said he didnt think it was the egr, since the 15mph test was fine. He thought it was some leaning situation, but wouldnt that also affect the other tests??

Here is a jpg of the two different tests.

any ideas on what to start with?

http://img523.imageshack.us/img523/7943/smogtestjb5.jpg (http://imageshack.us)
Shot at 2007-07-02

[MessyHonda]

time to SEAFOAM.....it says helps pass emission test...

[mbc]

Clean out your EGR port (between valve and carb) if the valve is still good. Then replace your catalytic converter. Your NOX levels will fall. Doing this will raise the HC levels a little, but you shouldn't have a problem there.

[mbc]

There are many threads regarding this topic. You will find other member's experiences through a search on this subject.
Matt

[snoopyloopy]

see if your state has a buyback program. if there's other issues w/ your car needing attention and they'll pay more than you'd get in a sale, turn it in as a gross polluter and get a new one.

[AccordEpicenter]

what year/model is this? How many miles?

[88Accord-DX]

Make sure you air intake is nice & tight for cool air. Clean out the EGR & knock out any carbon in the pipe. Last you can replace the catalytic convertor. Sometimes you can widen the plug gap a little & it helps. Not sure if you fuel injected, but injector cleaner & cleaning the 02 sensor helps out too.

Edit- Typically causes of high NOx emissions are high combustion temps, excessive high engine compression ratio, carbon deposits in the combustion chambers, low cooling system, blocked water jackets, etc.
EGR system problems- burned gases are not being injected into the intake manifold & combustion flame temps. are too high.


Here is a link to read about 86-89 Accord high Nox readings. http://www.usedcarmart.co.uk/forum/archive/index.php/t-7321.html