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Thu Oct 29, 2009 9:47 pm

Ive been through Oregon DEQ at the Gresham testing station 3 times now and have failed 1 time for high idle (fixed) and two times for 2 much CO (around 4.5 both times). I havent had to run a vehicle through DEQ for about 15 years so i am not used to this.

Does any one have any good tips for reducing CO? I was considering trying to lower it by leaning it out by turning the AFM screw to the left, is this a possible fix? Im hesitant to mess with the AFM as it appears to have some glue or something on the screw so I am not sure if this is a factory setting and something I should be messing with. I think allowable co is around 2.5

the stats on my paper work were this (the low HC makes me think its the AFM allowable HC is 300)

1st Idle: HC 95/ CO 4.582/ CO2 7.4
2nd idle: HC 105/ CO 4.457/ CO2 7.2

the bus is a 77 FI 2.0

Not sure if any of this affects but this is some of what i have done so far.
I have changed oil and filter, cleaned injectors, checked sparay pattern of injectors, replaced seals, fuel filter, new points, new plugs., new temp II, new air filter, lowered idle.

any tips would be greatly appreciated.

Thanks,

Thu Oct 29, 2009 9:56 pm

Pay off the inspector!

Thu Oct 29, 2009 10:02 pm

Thu Oct 29, 2009 10:23 pm

Do you have a catalytic convertor on the bus.

Find a smog shop who is willing to do a pre-test for you and set the CO. To begin with if you have a cat you have to measure it at the port on the bottom left of the exhaust. If you don't have a cat you can measure it inside the tailpipe.

At idle look for about 1.1% CO. At 2000 RPM look for 1.4% - 1.6% CO.

If the AFM is the orginal one and this bus has passed smog before then I would be concerned about what may have changed - fuel pressure regulator gone bad for example or sticky injectors. If this bus is new to you, you can't know what the PO did.

At idle, turning the AFM screw counter-clockwise opens up the passage and leans it. Turning it clockwise closes the passage and richens it.

Inside the top, the black cap, there is a big gear with notches and a wire shaped like a W that is held in with a screw. If you turn the big gear about 3 clicks clockwise it should drop the CO about 1% at 2000 RPM. If you decide to play with this you MUST mark it by scribing a line where you started because sometimes the gear will slip in your hands and you need to know where you began. Ratwell has a good write up on this but use the big wheel to change the mixture, not the small screw as he suggests. If you do it his way (no offense Richard) it will also affect the mixture at Wide Open Throttle.

Or you can ship it to Fuel Injection Corp in Livermore CA and let them rebuild it. They have an Internet site with an a online store at http://www.fuelinjectioncorp.com/ or you can call and speak with Robert W. White. They also have other bus FI parts. If you prefer you can also get the rebuilt FIC AFM's through I believe Scott at German Supply or BusDepot. The direct pricing is similar but it will also depend upon whether you want yours tested first as they will test it and apply the cost of the test to rebuilding or exchange. We had one they tested and it was perfect except out of adjustment. They put it back in adjustment and it passed smog. We picked up an excahnge one there and they have taken care of us. Although the inner boards are no longer available, they got us a really nice like new one and it should have a nice life. BTW, I asked Robert W. White (his dad is CFO and also named Robert) today if he had any luck finding new boards. He said Bosch said they will make them if FIC will buy $250,000 worth of boards so don't look soon for new AFM boards from Bosch. I would take a life time to sell that many new boards.

Like Richard Atwell recommends, I forked out the money to buy an Innovate LM-1 so I could tune the AF mixture. Then I have a smog guy who knows me well enough that he will do a pre-test for me when he is not busy and give me the numbers without charging me until we do the actual smog test. That way we have been able to tweak the AFM to perfection. Maybe one of the club members in Portland can assist with an A/F meter. We are in Sacramento and would be glad to help you but it would be a 1000 mile round trip for you to bring it here to adjust it. Kinda time consuming and expensive for a smog adjustment.

Last - it occured to me that one thing that could cause that bus to go rich if the AFM was set right once is that the EGR may not be working. It will lean out the mixture when it works because it allows exhaust gasses in. That reduces the amount of air coming through the AFM which leans the mixture. So you might want to check the EGR to see if it works.

Thu Oct 29, 2009 10:25 pm

tried this?
Take it out on a 15+ miler and get it good and hot. Don't turn it off while sitting in line at the DEQ, let it idle. See how it tests when good and hot.

Adjusting the AFM mix is not too hard just be sure to mark the original starting point. Clockwise is more Rich, Counter Clockwise is Lean. The adjustment screw under the rubber plug, not on the wiper.
OR
to do it right take it to someone with a tester, show them where the adjustment screw is. [so they don't start in on your idle screw] Have them dial it in to the passing specification.

Thu Oct 29, 2009 10:45 pm

K I will try it one more time by just running it on the freeway for about 15.
Also this bus in non catalytic.

If running doesnt work I will try turning the gear. If that doesnt work maybe I will call around to some of the local VW repair shops and see if any of them have the testing equipment and could tune it. I can imagine that would be too pricey, and I am leary of having a non VW mechanic do anything to the bus :P.

would refilling the charcoal canister help?? I heard you can get charcoal pellets from pet stores and refill them.

Thu Oct 29, 2009 10:52 pm

Quote: Clockwise is more Rich, Counter Clockwise is Lean.

That is reversed. On a 1977 motor, a 018 or 020 AFM, turning the spring clockwise makes the spring tension more and harder to open the door which leans it. If you undo the W-wire it will unwind counter-clock wise which makes the door easier to open (richer). I know someone here posted what you wrote but after spending the last three weeks fine tuning these I am sure of this. The air enters on the right side and the hinge on the door/flap is towards you. Tightening the spring clockwise closes the door/flap which cuts down the fuel supply. The more the door opens the more fuel the engine thinks it needs. I have one in front of me. If you don't believe me grab a used one and take off the W. See what direction the big wheel spins. It will unload with the part nearest the W going to the right, just like a clock going from 7 to 6 to 5 to 4. That is Counter-Clockwise.

Thu Oct 29, 2009 11:02 pm

Ok I will give it a try. The bus is new to me Tags expired about a year ago, who knows what the PO did to it, other than neglect it and park it once it died. It runs exceptionally well right now DEQ issue aside.

Thu Oct 29, 2009 11:16 pm

Richard has a good page that converts A/F to CO. It is at

http://www.ratwell.com/technical/afr.html

I have our AFM set to run at an air fuel mixture of 13.9 to 14.0 at 900 RPM idle. It goes to about 13.6 at 2000 rpm +/- with no load. On the road it idles at 13.9 - 14.0 air to fuel, drives at 65 at about 13.7 air to fuel and drops to about 12.7 on wide open throttle. This seems to be about perfect for this 1977 motor we just rebuilt, gets great power, passes smog and has just a tad of oxygen left at 2000 rpm on the dyno smog sniffer test so we have more fuel than air. Our EGR works and is adjusted per Bentley / Orange factory manual. If you have a cat then it will clean up the CO a little more. In California we must be below 1.66% CO at the tail pipe at test speeds of 15 in 2nd and 25 in 3rd.

Thu Oct 29, 2009 11:17 pm

SGKent wrote: Quote: Clockwise is more Rich, Counter Clockwise is Lean.

That is reversed. On a 1977 motor, a 018 or 020 AFM, turning the spring clockwise makes the spring tension more and harder to open the door which leans it.

I was referring to the mixture adjustment screw. Bentley - Chapter 10 page 26 section 5.2 - 6 >> Clockwise is Rich

Fri Oct 30, 2009 8:15 am

that link appears to be broken but i should be able to find it on ratwells. Is there a bently manual online PDF or something? i do not think I have one. Ill look in the glove box there was a riviera book ill see if the other is in there. I have the big green service manual, a haynes, and John Muirs book for idiots :P

Fri Oct 30, 2009 8:24 am

If all fails, take it to Trafton's Automotive out in SE Portland. They can adjust it for you for not much money and Bill is a heck of a nice guy.

Fri Oct 30, 2009 10:33 am

bjjpdx wrote: that link appears to be broken but i should be able to find it on ratwells. Is there a bently manual online PDF or something? i do not think I have one. Ill look in the glove box there was a riviera book ill see if the other is in there. I have the big green service manual, a haynes, and John Muirs book for idiots :P

That big green service manual is what folks refer to as the Bentley.

Fri Oct 30, 2009 11:40 am

Also do a valve adjust and check timing. That's all I did w/my '76 2.0L and I passed DEQ easily (no CAT, EGR disabled).

Yeah, you wanna be carefull about monkeying around w/the AFM. People mess with it when it's rarely the problem and then that causes additional headaches.

Make sure you don't have any vacuum leaks. If in doubt, get new hoses. They're not expensive and they're easy to replace. BTW, those fuel lines in top condition? You don't want an engine (and then BUS!) fire. Fuel lines are the most over-looked replacement item on older cars and they're the cause of many a loss :(

Fri Oct 30, 2009 4:33 pm

Air_Cooled_Nut wrote: be carefull about monkeying around w/the AFM. People mess with it when it's rarely the problem and then that causes additional headaches.
(

Thats interesting as mine has been the source of many issues, and monkeying with it has solved those issues [bucking / hesitation].
I wouldn't recommend trying to adjust the mixture by modifying the wiper, but adjusting the mixture using the standard mix adjustment screw is the only way per the manual to to do this. Just mark the starting point and don't get carried away with huge turns of the screw, a small bit of turning goes a long way.

Fri Oct 30, 2009 7:19 pm

worste case Traftons is about 10 minutes from my house. Been in there a few times already. All my hoses are new, first thing I did. fuel hoses getting replaced this weekend, along with tuning the AFM

Fri Oct 30, 2009 7:31 pm

I didn't read all the posts but Oregon deq only checks emissions at idol. I have had extremely good luck on vehicles that wont pass when I increasing the idol speed as high as I can get away with. By all means get it tuned but if you just need to get it threw before the end of the month its worth a shot.

Fri Oct 30, 2009 8:30 pm

Yea I had it high, even failed once for too high of an idle, its real rich any way i can smell it, best to adjust it.

Fri Oct 30, 2009 11:25 pm

If the shop is only 10 minutes, take it to the shop and let them adjust the afm. You really need a tachometer and a wide band air fuel meter and/or a CO sniffer to get it right.

Fri Oct 30, 2009 11:29 pm

Quote: I wouldn't recommend trying to adjust the mixture by modifying the wiper, but adjusting the mixture using the standard mix adjustment screw is the only way per the manual to to do this

FYI - that AFM screw ONLY adjusts how much air bypasses the meter. It affects mostly idle and just off idle. You are talking of passage about the side of a pencil eraser with a screw stuck in it that opens and closes it - whereas the metering flapper is huge in comparison. The metering flap/door is controlled by the general placement of the wiper and the spring tension on it.