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Thu Jan 15, 2009 6:13 pm

I just got home form the local smog check station. I failed do to "Too Lean at Idle" syndrome.

State requires 5% CO2 at idle.

The OXY is also too high at 15% and should be around 1 to 3% for the state.

I could get no more than 3.8%

Everything is fin at upper RPMs and in spec.

O2 sensor checked correct.

The tester played with the wheel in the AFM, but no change. Ended up going back to where it was.

I have done all the obvious, Plugs, wires, cap rotor, fuel pump, fuel filter, air filter, Cat is also new, etc..

Any ideas on how to richen my idle mixture.

Any suggestions would be greatly appreciated.

Thu Jan 15, 2009 8:23 pm

A minor vacuum leak will cause a lean idle and will not affect running at heavier loads. Lots of threads out there on vacuum leaks.

Thu Jan 15, 2009 8:28 pm

I have found that I have to run the van on the free way for at least ten minutes at a good clip before I take it in.

Thu Jan 15, 2009 8:29 pm

Could be sucking unmetered air. means a vacuum leak. Put a vacuum gauge on it for readings.

Hopefully the tester put the black toothed wheel inside the AFM back to (zero). From there you should be able to richen the mixture.

Also, the idle mixture screw on the AFM, in my experience, is out ~6 turns to pass smog. Mine runs better at 2-3 according to seat of the pants testing. But you could try to have this seated ( closed ) and back it out from there to get the idle numbers. Some of the idle mixture screws use a slot type screwdriver and some use an allen wrench. Check for yourself how many, full, turns it takes to gently seat the screw. If less than three, I doubt the mixture can be adjusted via the AFM and you'll have to look else where.
Another point about the AFM is that the epoxy seal that is used to glue the thing together, along with the rivets, breaks down and causes internal unmetered air. This info comes from an FI rebuilder. So, see how many turns out the idle mixture screw is. How old is the AFM?

This should help get you started.

Thu Jan 15, 2009 8:33 pm

The first two suggestions posted are a great starting point. To have the thing smokin' hot before strapping yourself to the dyno is the best advice to grab a baseline.

Thu Jan 15, 2009 8:49 pm

Thanks for the tips. I had the bus pretty hot and it was running for about an hour in the shop.

He did poke around with a smoke wand looking for vacuum leaks with no luck.

170K miles on this boy.

Where is the mixture screw? I hear you have to drill something to get to it? Any pictures? I'm clueless.

I was surprised how far he turned the black toothed wheel on the AFM wheel with absolutely no change in the readings. Ended up back where it was when we started.

Thu Jan 15, 2009 9:08 pm

The mixture screw is right on top of the AFM. It may have a black rubber plug about 1/2" in diameter. Once you see it, you'll have the "Ah ha" moment.

Also. instead of moving the cog, just gently push/bump the wiper assembly about 1/4" back and forth from its idling position. You should notice the engine sounding different with this slight movement. It should increase the idle rpm a bit and/or smooth out the idle quality when moved CCW. Move it more and it should get doggy.
You will be able to watch the smog results from this. But you can check these parameters yourself just for the knowledge if nothing else.

Could check fuel pressure to make sure the regulator is uo to the task. The vacuum source is ported. Moving it to manifold will increase fuel pressure. Would be a temporary fix to pass. Then just put it back to ported.

Fri Jan 16, 2009 10:27 pm

Looks like I might be out of luck with the CO2 adjusting screw to get the mixture more rich at idle. I checked it and it is 1.75 turns from all in.

Bummer !

Fri Jan 16, 2009 10:44 pm

Inside the AFM there is a spring. How many coils do you think it has. If it's two or three, or five or six, that's obvious. Doesn't have to be exact.

Point is that if it has ~three coils, adjusting the black toothed wheel should show results with 2-4 clicks either way. Mine has about 6 coils. Makes for a lazier sweep. I can adjust to ~10 clicks either way. I can go a bit more but my mind tells me I am too far off before the engine responds as poorly.

You should verify correct distributor timing, vacuum readings, and fuel pressure readings. Using the Seafoam FI cleaner can be tried. Maybe the injectors are dirty.

How much maintenance or when was the last time maintenance was done. Sans the most recent for the smog tests. Trying to picture the vehicles history.

Does it have EGR. Can you scan and post the print out?

Fri Jan 16, 2009 11:03 pm

regis101 wrote: Inside the AFM there is a spring. How many coils do you think it has. If it's two or three, or five or six, that's obvious. Doesn't have to be exact.

I guess I would have to pop open the top. I am not sure The guy at the shop was messing with it and ended up putting back to where it was. He did not however adjust the CO2 screw which I uncovered tonight.

regis101 wrote: You should verify correct distributor timing, vacuum readings, and fuel pressure readings. Using the Seafoam FI cleaner can be tried. Maybe the injectors are dirty.

Checked the timing and it was right on. i use fuel injector cleaner all the time. I guess I will have to check the injectors next. Haven't tested the fuel pressure regulator yet. not sure how to actually.

regis101 wrote: How much maintenance or when was the last time maintenance was done. Sans the most recent for the smog tests. Trying to picture the vehicles history.

Does it have EGR

It has had alot done last month. Cap, rotor, wires, plugs, fuel filter, fuel pump, air cleaner, coil, coolant, cat, exhaust, 02 sensor was tested. I don't think the 1990 2.1 has EGR.

I can also hear the throttle position switch clicking on both throttle closed and full open.

This bus runs like a top, just can't hit that 5% CO2 requirement at idle!!!

After all this SAMBA reading it really makes me want to dump this AFM regardless if it is good or not for a Hot Wire system.

Sat Jan 17, 2009 8:03 pm

Well a happy ending...

Went back to the smog station and we played around with the fuel pressure regulator buy unplugging it and the mixture did richen as is should. We searched and searched for any leaks no luck, even messed with the CO2 screw and nothing. Unhooked the O2 sensor and nothing seemed to work. Was just about to give up and he pulled the sniffer and reset it. Then he really jammed it it the muffler as far as it would go much farther than previous tests and BINGO everything was right on the money !

Moral to this story, "Stick that freaking sniffer way in there !"

Sat Jan 17, 2009 9:42 pm

That's good to hear. I broke out the Bentley and started going over other possible things to look at. But you're good for another two years . How did the gas tank test go. Must've been OK

Sat Jan 17, 2009 9:50 pm

Next time take to a place that deals with Vanagons on a constant basis.

I have to take mine for smoke testing again.

I've only driven it a few thousand miles in the last 2 years.

We'll see how it goes this time.

Sat Jan 17, 2009 10:28 pm

regis101 wrote: How did the gas tank test go. Must've been OK

He said that they have to do the tank test as a state requirement, but as of right now its not a pass or fail item. If the tank fails they are to encourage you to fix it, but if you pass the smog your good. This will be until next year, then I think your cooked if the tank fails.

He did another Vanagon a couple weeks ago and the tank vent test failed as did mine.

They hook up a special cap and pressurize the tank way up and if it starts bleeding down all kinds of alarms go off. Mine failed miserably. Looks like I have to drop the tank and replace all the hoses on the venting and check the plastic bottles for cracks or leaks. If I recall I had one of those tanks out and it has some sort of lid on it. Mine might be messed up. Now one more thing to have to fix to make CA happy. He mention diesel engines will be required to take state smog tests starting in 2010.

While I have the tank out I will do the TK stainless one piece coolant lines.

More money...Ugh!

Tue Aug 29, 2017 11:54 am

Had a similar experience this week with the smog testing in Reno, NV. That is, dilution in the exhaust at idle. At first, I thought I had issues with the new RMW exhaust with CA cat or the Vanistan engine. After a few days of running around, re-torquing bolts on the exhaust, retesting, I made a last ditch effort to try a different smog shop. It passed. whew.. Was going to have the van at the mechanics to trouble shoot and made adjustments and retested. Could have been an expensive ordeal.

It is likely that the original smog shop had equipment out of calibration.

Frustrating couple of days ended well.