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Date:         Tue, 22 May 2001 23:42:13 -0600
Reply-To:     Steve Blackham <steph@uswest.net>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Steve Blackham <steph@uswest.net>
Subject:      Confessions of a Emissions Passer
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

We are not talking a flatulent here!

Last summer on my trip through the northwest my catalytic converter began to ring like a bell. When I returned home and removed it, the goodies inside just fell out in crumbs. Not having a spare $120 I just put the empty shell back on. It has run great ever since.

Anticipating trouble in getting past my yearly emissions test this month I started a month early. April-17 I got my first test with the following readings:

2500 RPM (actually 2629) HC CO% Standard 220 1.2% Readings 87 0.87% Passed Passed Idle (923 RPM)

Standard 220 1.2% Readings 871 1.53% Failed Failed

I think these figures don't look like they are caused by the cat. Cruising is fine, idle is the problem and HC is the problem. It's running slightly rich at idle. Hmmm. Better check the exhaust system for leaks before the CAT. Sure enough, the exhaust manifold Y gaskets are shot again and leaking just enough to corrupt the exhaust mixture at idle. I replaced these gaskets and tried out my new CO meter I ordered from JCWhitney (critique coming later). I found it still hard to get the correct CO values for both idle and 2500 RPM. When I would get it right for one it would knock the other off. Idle still seemed to be the problem. Adjusted it to the best place I could get and took it back for another test as follows:

2500 RPM (actually 2583) HC CO% Standard 220 1.2% Readings 57 0.84% Passed Passed Idle (987 RPM)

Standard 220 1.2% Readings 338 1.01% Failed Passed

Better but still not quite there. Why was CO within range but HC still high. Originally thought it was the FPR (fuel pressure regulator) because my idle readings appeared to be 31 #s. Well, I ordered a new one and the new FPR came up with the same readings. My gauge must be a couple of #'s off. OK thats not it, WHAT? I took an hour or two and reread my "Probst" fuel injection manuals which seem to indicate that normally high HC levels are ignition problems. Since I just replaced the plugs and the rotor still looked good I figured I'd better look at timing. I had originally thought that the digifant ignition system was like the new Ford systems where you didn't need to adjust the timing unless you had disturbed the distributor. In checking "Bentley" I find not so. I followed the directions in Bentley for checking timing with a timing light, disconnected the Temp II wires, and the engine went immediately to 2500 rpm. This is the speed that " Bentley" says that is necessary to test timing. The readings show that it is about 20 degrees advanced. I adjust the distributor housing to bring the reading to the case half mark and the engine drops in speed. The exhaust immediatly turns from the pungent smell of high HC to a more normal smell.

I re-adjust the idle and 3000 rpm CO readings using both the CO meter and a volt meter on the O2 sensor and things seem to match this time. The engine seems to purr. It doesn't hunt any more. Road test shows good power in all loads. Great I think. She should pass this time.

This morning, I took her back in for a retest. A little gun shy I ask them to just test the CO amd HC readings off the county system first to see where we were. CO was fine at about .6% . HC was still a problem at around 300. I quickly pulled an allen wrench and screw driver out and began adjusting the AFM and throttle body idle adjustments. By raising CO a little, HC seemed to drop. Understandable if you've ever seen the relation between these two charted. If I raised the idle up a little to the mid 900's things seemed to get better. HC dropped to around 80. Not bad for a vehicle without a CAT. This should do it and asked for the official test:

2500 RPM (actually 2574) HC CO% Standard 220 1.2% Readings 32 0.72% Passed Passed Idle (977 RPM)

Standard 220 1.2% Readings 130 0.84% PASSED! Passed

In retrospect, my problems seemed to be an exhaust leak, bad timing, fine tuning of the AFM wheel, air by pass and throttle idle setting. No doubt a fresh CAT would improve these figures but this is not bad (for me or the enviroment).

One down and eleven more to fix ( or at least adjust). My son's Jetta is next on the list. Oh, the whoes of a multi-VW owner.

-- Steve Blackham Centerville, Utah

77 transporter converted to camper (Westy top) 83 Vanagon (New and current project) 87 Weekender


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