1G failed smog, rough idle

er82 · Jan 24, 2015

I tried to pass CA smog test for my 90 DSM AWD but it failed at idle due to high HC.
I changed spark plugs and gapped to 0.032", ignition coil, changed oil to 20w50, filled up tank with fresh gas. It's got spark plug 10mm spark plug wires. Cat is from another DSM that's been sitting for a while. Although, I don't think the cat is the issue as it passed 2500 rpm test (pic attached).

Here is link to idle video (smoke is vapor because it's cold):
http://s236.photobucket.com/user/edya19/media/IMG_1765_1_mpeg4.mp4.html

Compression:
#1 180
#2 150
#3 160
#4 175

Would that compression cause rough idle and fail the test?
All the vacuum lines appear to be connected, soft and flexible. Car is stock except for intake filter. I tried to pass test twice, second technician said it idles like it has a cam. As far as i know it's all stock.
Anyone have any ideas?

badassgsx · Jan 24, 2015

I was having smog issues also
and my solution was a new catalytic converter.
You will pass with flying colors believe me
Just buy an aftermarket cat and have it welded on
shouldn't cost too much

er82 · Jan 24, 2015

I was trying to avoid buying a new cat as the CA certified ones are $300.

badassgsx · Jan 24, 2015

Just buy the 100.00 or less cat and weld it up
i am in ca also
I tried everything and that was my solution new cat = passed smog

DSM1G90 · Jan 26, 2015

I failed HC also on the first sniff test even though I have a very smooth 750rpm idle and no CEL, but a good tune, new BPR6EY (grooved electrode) plugs at .028 and a fresh oil change of 10/30 got me in specs again .. with a motor with almost 100K miles on it.

er82 · Jan 30, 2015

I got a new cat and it improved the reading by 4 times, but still failed HC test. It measured 360 and allowed is 120. I guess next to try would be MAF and o2 sensor. Any other ideas? The car also wants to stall on a hot start for first few seconds or so. I'm not sure if this is related.

enriquez2000 · Jan 30, 2015

er82 said:
I got a new cat and it improved the reading by 4 times, but still failed HC test. It measured 360 and allowed is 120. I guess next to try would be MAF and o2 sensor. Any other ideas? The car also wants to stall on a hot start for first few seconds or so. I'm not sure if this is related.

cheat the test? weve done it out here by adding 2 gallons of e85 to half tank of 91.. drive around and get your cat really warm and voila...

You can also drop your exhaust before the new cat and do the intake seafoam to clear carbon then bolt the cat back up.. sometimes things just get dirty and need flushing. Just dont do it with the new cat attached

http://seafoamsales.com/vacuum-line-method-with-sea-foam/

er82 · Mar 2, 2015

enriquez2000 said:
cheat the test? weve done it out here by adding 2 gallons of e85 to half tank of 91.. drive around and get your cat really warm and voila...

You can also drop your exhaust before the new cat and do the intake seafoam to clear carbon then bolt the cat back up.. sometimes things just get dirty and need flushing. Just dont do it with the new cat attached

http://seafoamsales.com/vacuum-line-method-with-sea-foam/

An update in case anyone was interested. I did the seafoam procedure. Though I didn't see the smoke come out of the exhaust. I cleaned the MAF and changed the o2 sensor. Then I drained the fuel tank to about 1/4 tank. Before the test I got it warm, drove on the freeway (1 exit) and filled it with 2.5 gallons of e85. So it passed the smog test.

Thanks for the help.

DogWhistle · Mar 2, 2015

Awesome! Glad to hear you passed. E85 FTW. Surprised it's that tough to pass honestly. Hope we never get SMOG or Emissions back in MN.

enriquez2000 · Mar 2, 2015

er82 said:
An update in case anyone was interested. I did the seafoam procedure. Though I didn't see the smoke come out of the exhaust. I cleaned the MAF and changed the o2 sensor. Then I drained the fuel tank to about 1/4 tank. Before the test I got it warm, drove on the freeway (1 exit) and filled it with 2.5 gallons of e85. So it passed the smog test.

Thanks for the help.

I use this procedure on so many cars and it almost always works. Sometimes you have to mess with the tune if you run rich but e85 has almost no emission output. And i love the smell of a pure e85 car.

steve · Mar 3, 2015

Every time I failed it was due to a old/slow O2 sensor. I see you changed it.

There is nothing to clean in a DSM MAF unlike a hot wire MAF in other cars. For future reference.

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1G failed smog, rough idle

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