For the 3rd time, my 3rd Maxima, I'm having to learn that I have low compression in a cylinder during SMOG time.



I have a 92 SE in California. What are the options for this VE30DE?

 

They actually compression test each cylinder in California!? Wow.

What exactly are you asking though? Are you asking how to fix it? Are you saying they failed your car and you have to get the compression in that cylinder up to re-test? Not sure what your question is.

 

No, they aren't doing a compression test.
I'm not passing because of my High HC. I did a search but nothing here tells me on what to fix.
Meanwhile I visited the mechanic and they discovered the low compression. 120 on Cyl 4. 170 on the rest.

 

When is the last time the cat was changed? Some high flow cats don't seem to last more than a couple years. Anytime i've failed emissions its been due to the cat. This time i managed to find myself a brand new oem cat so the next magnaflow cat that goes i'll replace it with the oem which should last much longer though there are some descent aftermarket cats you could put on for your test then put the high flow back on afterward if your running a high flow cat but with high hydro carbons its probably cat or o2.

 

You can almost surely still pass emissions with low compression in a cylinder. I have year after year after year.

I would much more quickly suspect incorrect timing or even a bad cat over low compression in one cylinder throwing you over the threshold into failing emissions.

What is your HC limit there and how high over that limit are you?

 

I'm only failing the 15mpg test.
HC Measured 98, Average 30, Max 78.

So I was recommended doing thick oil and an oxygen sensor. But do all signs lead to the cat?

BTW. Thank you for your inputs. This made me feel bummed all yesterday.

 

I'd lean towards the cat but when is the last time you changed the o2? Setting the timing can make a diiference too but i think a new cat would do the trick and drop your high hydro carbons lower than what a timing adjustment will get you. I actually went through that issue on my last etest and took it for a retest after having the timing adjusted and it did effect the numbers. I did that a couple times before just bitting the bullet and changing the cat. I cant recall the changes the timing adjustments made but it was either advancing or retarding the timing changed the numbers at high idle and changing the timing the other way changed the numbers at low idle (7500 rpm) but still couldn't get the numbers in spec. but after swapping the cat it passed with flying colors bringing the high hc way down well within spec. I also did the o2 for piece of mind before the first retest and after having the timing adjusted and still no pass.

 

Thank you for the info. I bought a new O2. So, let's see.
If it is the cat, is it a good time to buy the 3 inch exhaust?

 

Really don't think a 3" exhaust is necessary unless your planning on boosting it. If your not planning on boosting it put that money into a cattman ypipe or warpspeed if they still have em. I don't think a 3" pipe is going to do much for you if your not boosted though.

 

OK, (ACMax92)
After the O2 replacement, the HC values were worse. i guess it's Cat time.

 

Yes sir cat should do the trick.

 

The new Cat did the trick. Thank you!!!!!
Good for 2 years.

 

Figured it would. Glad you got it sorted out. If you got a descent aftermarket one it may last longer. I just went with the magnaflow high flow cat at the time because they were cheap until i found a new in the box oem cat that i never would have bought new from the dealer at a grand. I just really lucked out finding one in the local classifieds new in the box never installed for under 100. I don't even think the seller really knew what it was even worth. Anyhow if you have the flanges still and your cat is a bolt on you could probably bolt your old cat back on and save the new one until next time you need it. Just a thought.