[ba] 5 cylinder now idles - but still not making the grade smog-wise

[Steven B]

NOx is usually a result of high compression or high combustion temps.  Have you noticed pre-ignition at all?  It would be worthwhile to run compression numbers on all cylinders, perhaps you have excessive deposits on the combustion surfaces.  What can cause high combustion temps?  How warm are the engine coolant and oil getting during the test?  
 
I'm not sure I agree with the comments about the newer cats ... 3-way cats require the injection of air into the exhaust for the third catalytic reaction.  I'm sure the high price of cats in California now is a direct result of the new laws this state has enacted regarding catalytic converters ... they have to be somehow certified for the specific application, and installed by a certified smog technician.  "certified" = $$$$  I'd bet all that a "certified" cat is for a car as old as we're talking about is would be a new part from Audi.  There is little doubt that a new cat would help, but it is always best to see if you can make it without having to spend too much ... 
 
Steve Buchholz

From: Michael Heth <classic_coupe at serversmiths.com>
To: ba-group at audifans.com
Sent: Saturday, September 10, 2011 8:12 PM
Subject: Re: [ba] 5 cylinder now idles - but still not making the grade smog-wise


On Sep 6, 2011, at 7:22 AM, k1drbar wrote:

> I'm sorry Michael but I don't remember what model year your car is ... if
> you are messing with the idle screw I'm assuming it is an older model
> without an ISV.  
> 
> One of the first things I do when a change results in unexpected behavior is
> to eliminate the part I just changed as the culprit. 
> 
> I hope that you are able to find the manual as it has some good instructions
> for troubleshooting.

> Good luck!
> Steve Buchholz



Say Folks,

Thanks much for all the tips and advice.

To be clear(er) it is a 1982 URQ(MiniMe), the original Coupe GT. (It now gets lots of attention since the great unwashed have finally figured out that Audis are actually very cool and capable cars - they all assume it is a full fledged URQ).

I had noticed (when I first went to change the air filter) what I thought was a torn hose but when I looked again I couldn't find it (so I thought it was my imagination). In the work of reinstalling the large rubber boot of the FI, the hose had been severed and dropped down out of sight. The upper portion was just barely discernible once I had it all apart again. So I sealed it all back up (what are the chances of being able to find a custom bent FI hose for a 29 year old car? I figured "nil" and went with a repair which came out fine - cost about $.15).

So then we were starting and idling just fine. I (optimistically) took it in for a retest. The nitrogen had gotten better and passed on on the idle portion but the 1500 RPM figure was still 150 PPM too high.

So now I have to figure out how to get that down.

The test tech said it could be the Cat since mine is 7-8 years old. But I thought I had bought a pretty good one @$150 from an outfit in Oregon. He said I should be able to find a way to test it myself (they have a repair outfit behind their "test only" facility and are cagey about clues since they want me to use them to sort it out).

I know some folks have sometimes squeezed past by running a particularly clean fuel but I'm already running Chevron Premium so I think I'm there on that point.

I doubt the timing could have anything to do with it as everything except the 1500 RPM nitrogen is just peachy.

As alway, any tips advice much appreciated.

M./

Michael Heth
classic_coupe at serversmiths.com



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