I've searched and couldn't find much info about others who just failed the idle test.

Its a customers car I just put back together after a full rebuild, everything went back to stock and it seems to be functioning very well.

It passes the e-test in the higher rpm with flying colors, which tells me that the cats are good, but the idle is waaay off.

HC ppm limit 200 it reads 573
CO% limit 1.00 it reads 4.52

Any idea why? I replaced the 02 sensor and it idles perfectly at 800rpm. Now when we did the test we pulled off a little vacume cap thinking it might make it run lean at idle to help pass but no dice.

 

Is the air pump functioning properly? Were the cat's thoroughly warmed up before the test?

Dave

 

To me, that much HC is telling me that it's running too rich at idle.

One suggestion which I always follow (not sure if it's even 100% accurate though)...

Disconnect the vacuum hose on the purge control system where it meets the front side of the intake manifold (near the throttle plates) and plug the holes up. This would be in between the check valve and the manifold.

The internet-wisdom (aka possibly an urban legend) is that if the purge system vents off evaporative emissions into the manifold while you are testing, you get a burst of HC. I am not sure if this system functions at IDLE or not... I don't have my service manual here.

Pulling off vacuum hoses will not work on an FD because it has no airflow meter.

 

Right I know that pulling off a vacum line wont technically effect it because of the lack of an AFM, but if I pull it off after the TB it should suck in air and make it run a bit leaner...sorta...it was worth a try anyways lol.
The air pump does kick on and I drove it around for a good half an hour before the etest, so the cats should have been warmed up.

 

Oh one other thing, the muffler has a bunch of holes in it, its all rotted out at the bottem. Would that effect it? It wouldn't make sense to me but I thought I should mention everything that is wrong with it lol.

 

What kind of cat is on the car? MAybe it's clogged or hollow or not there at all?

 

The muffler shouldn't make any difference. Set the idle at 950, and check it again. For some reason, some FD's seem to run cleaner with a slightly elevated idle.

 

the muffler makes no difference. what are the 2500 RPM numbers like Joe?

 

Didn't think the muffler should matter. The cats that are on it are original Mazda cats, I checked them and they are all there and are clean, not broken up or clogged.

Heres the full report from the last test we got done

2500rpm reading
HC ppm - limit 60 it read 58
CO% - limit 0.33 it read 0.00
NO ppm - limit 450 it read 224

Curb idle
HC ppm limit 200 it read 573
CO% limit 1.00 it read 4.52

That test was done with 4 liters of Karosene (sp?) in the fuel tank when it was almost empty. The etest guy said that Karosene makes them burn cleaner at idle. We also tried Mythel Hydrate in previous tests, and the curb idle was a bit better but still wouldn't pass.

Any other tricks

 

Are you sure you have got proper and full combustion at idle??? Cause a combination of high HC and CO usually means incomplete combustion.....
If you want some sort of certainly about this, plug in a new set of plugs, let it idle for 10-15mins, switch off and remove the plugs. Check them for gasoline residu and colouration...

 

Again, is the air pump working correctly? If it is not, you won't pass, and it is more critical at idle. Also, just because the cats are working somewhat, does not mean they are not partially coated and disabled.

However, I still suspect a faulty air pump (or its controls or piping). The air-pump air is needed to oxidize the excess HC and CO due to the rich mixture at idle. And, since not much exhaust is flowing at idle, the air pump is definitely needed more at idle than at higher revs.

 

try lifting the rpm up for the idle test like 1000 or so and see how the numbers are. also it looks like the o2 is not working at idle or it is running really stinkiy rich. does it smell at idle enough to burn your eyes?

 

Like he says!