emissions trouble 3.0 HELP

jwittb · 05-16-2007, 11:52 AM

Here goes.

I am new to 911 but have been trying to educate myself by reading this site quite frequently. Last year I bought a '77 with a 3.0 CIS installed by the PO. It failed emmissions, so being in Memphis I took it to Pat Williams Racing. When I picked it up he said it would pass (it did) and after inspection I should run it back by his shop so he could tweak it for better performance. He wrenched on it in the parking lot for about a minute and pronounced it ready to drive. I know he adjusted the timing but being ignorant about CIS I have no idea what else he was doing. Anyway it has run terrific all year but now it is time for inspection again and I would like to be able to tweak it myself to pass emissions and then tweak it back for the road.
First trip to inspection: Hydrocarbons (HC) = 706ppm
HC limit is 600ppm...FAIL
CO 0.88%
CO limit 7.5%...PASS
(all tests are at idle)

Following tips I read on other posts, I filled up with low octane gas and ran the car hard on the way to the station. Nice and hot.
Results?
HC = 1116ppm
CO = 0.71%

So after reading a few more tips I put a gallon of ethanol in a full tank of gas and retarded the timing. I dont have any means of measuring the timing but I would say I moved it about a fifth or at most a quarter of the available travel in the slot for adjustment. This dropped the idle about 100-150 rpm.
Results?
HC = 1131 ppm
CO = 0.53 %

Now; I could always take it back to PWR but I would really like to know how to do this myself. Should I have advanced the timing instead of retarding it? (I moved the distributor CCW) If advancing the timing is the ticket could I just disconnect the vacuum line for the retard? If I remove the line from the right (passenger) side of the thingy on the side of the distributor I get an RPM increase at idle. Can I produce the required change with timing only or do I need to monkey with idle mixture as well? Richer or leaner? Anything else I can do quick and easy just so I can pass the sniffer test, and then undo after?

Thanks in advance.

John W
1977 911 sunroof coupe
3.0 CIS
backdated exhaust (no cat)

81 911 SC · 05-16-2007, 12:02 PM

My guess is he leaned out the mixture. Thankfully I don't have to worry about emissions testing on my SC anymore.

jwittb · 05-16-2007, 01:11 PM

I thought that the CO reading of less than 1% indicated that the mixture is plenty lean already. Or did you mean he leaned it out after the emissions test?

John W

jwittb · 05-16-2007, 06:12 PM

OK Tyler, I'll bite. Why don't you have to worry about emissions any more?

jwittb · 05-17-2007, 06:01 AM

Not having a gas analizer, I am relying on my fellow pelicanites to pass the emissions test. Anyone...anyone...Buhler?

Side question: My engine has had the fan support repaired and the serial numbers have been welded over. Model # is 930/16. Is the fact that I have two lines to the distributor mean that it is a post 1980 3.0 or can that distributor have been stuck on the earlier 3.0?

Travis Neff · 05-17-2007, 01:13 PM

HC is unburnt fuel, CO is partially burnt fuel.

High HC is usually due to poor ingnition system. How is your plugs, wires, cap & rotor??

I have the same issues with my 914 every year. especially at idle - if I richen up the idle mixture I pass (granted I have fresh ignition parts.

You don't state if these readings are loaded (done on roller dyno) or at idle

jwittb · 05-18-2007, 08:09 AM

Thanks Travis. All tests are with no load at idle.

I have not replaced any ignition parts since I've had the car (only a year) but the wires and cap look new. Haven't had the plugs out either.

How would you check the rotor? What are the signs of a worn rotor? Since retarding the timing seemed to be counterproductive should I try advancing it?

I know parts can wear in a year but it passed last year with the current ignition parts.

Thanks

John

81 911 SC · 05-18-2007, 08:36 AM

No emissions testing in NH for cars older than OBD II. Besides I would never pass with not CAT, O2 sensor, and PMO Carbs on my car. I am the EPA's worst nightmare.

jwittb · 05-18-2007, 09:02 AM

No such luck here in the Bluff City. If you want to register your Model T Ford in the city of Memphis, its got to pass emissions.

John

81 911 SC · 05-18-2007, 11:34 AM

Wow that is too bad. Do they make the car pass current standards or the standards that were set at the time the car was made? I would think that it would be near impossible to make an older car meet todays standards.

jwittb · 05-18-2007, 11:47 AM

As far as I know they just made up some standards of thier own.

HC 600 ppm or less
CO 7.5% or less

I have advanced the timing to the point that it idles at 1100 RPM when warmed up. Gonna take it to inspection and try again.

John

jwittb · 05-19-2007, 07:25 AM

OK, deep breath...
Better, but it still flunked
HC=782
CO=1.03%

I figured that I was getting closer by adnancing and seeing as I brought my 13mm along with me for just such an occasion, I proceeded to advance the sucker all the way to the stop. This produced about 1600 RPM. I can hear the teeth grinding from here so before any medical bills are produced I will tell you that I only idled around the parking lot. The car had no power at this state of advance. Even at 1600 RPM I had to let the clutch out slowly to keep the engine from dying. Anyway I got back in line and...

Results
HC = 967
CO = 0.81%

So my next step was to pull all my hair out. After that I set the timing back to where it was before I messed with it. (Suprisingly, I had the foresight to mark it.) I then drove home and parked it and had some cocktails. Ah, but today is a new day; and hope springs eternal.

But I need some ideas to try now.

I read a post that suggested plugging one of the injector lines thereby making one cylinder an air pump. I actually started doing this but could find nothing to plug the line with that didn't spray my engine with fuel. I'm no automotive engineer, but I figure soaking the engine with fuel and filling the back end with explosive fumes is undesireable. Any ideas for plugging the line? I thought about pinching it off with vice grips but the line doesn't feel like it would spring back from that.

Where did you pelicanites find your long allen for mixture adjustment?

Thanks

John

jwittb · 06-25-2007, 01:20 PM

In case anyone is interested, I finally got around to trying the test center again. I pulled the banjo fitting for the #1 cylinder off of the fuel distributor and replaced it with a short bolt that fit the threads; leaving the injector and line in place.

Results:

HC = 497.25ppm PASS
CO = 0.70% PASS

Inspection has been passed!!! I am kinda suprised that this shade-tree solution worked. But then again when you think about it, it makes sense. By diluting the exhaust with fresh air you would naturally reduce any measurements taken in percentage or in parts-per-million.

Hope this helps somebody else out there who might be having similar issues.

JW

PS: Ran a little rough but not as bad as I expected. I pulled into the parking lot next door to the inspection station when I left and reconnected the fuel line in all of about 90 seconds. Runs great again.

tcar · 06-25-2007, 01:33 PM

Does the car still have the air pump?

jwittb · 06-25-2007, 06:58 PM

No. No air pump, no catalitic converter either. It has "non catalist" written in the door jamb (or maybe on the window) but the car is a '77 and came with a 2.7. Now it has a 3.0. It also has backdated (pre '74?) exhaust.

But, Memphis does not look at the engine or exhaust. They don't care what is in the car; only what is coming out the tail pipe. I can't believe I'm saying this but that city policy seems completely reasonable to me.

JW

john walker's workshop · 06-25-2007, 08:14 PM

i've posted the plugged injector trick a few times. turns the dead cylinder into an airpump and the HC drops way down.

dvkk · 06-26-2007, 12:15 PM

Beware, the plugged injector trick works by diluting the total exhaust. In some smog testing the amount of oxygen is measured to detect just this trick (including exhaust leaks) and they multiply your reading to compensate for the dilution. So that trick does not work in some states.

Your CO readings that are below 1% (sans CAT) could stand a slight richening. You are on the verge of lean misfiring if your ignition isn't in perfect condition. One lean pop will send the HC readings through the roof causing a fail.

You need to invest in a timing light. Sears has one that's $50. Find out where your timing is now, then a 3-4º retard will really bring the HC numbers down. This is what the wrench did in the parking lot to get it to pass the first time.

jwittb · 06-26-2007, 12:30 PM

Although the results are displayed on a computer, I don't think Memphis' equipment is that sophisticated. (Not to say that this is the case elsewhere)

dvkk... is a "lean pop" audible? I think you could be on to something here; however I can hear no misses at idle and it feels smooth as glass.

Not that it matters now (at least for another year) but my mechanic last year tuned it on an exhaust alalyzer. He just "un-tuned" in in the parking lot after it passed. I guess he didn't like where he had to put things in order for it to pass emissions.

JW

dvkk · 06-27-2007, 12:45 AM

Quote:

Originally posted by jwittb
... is a "lean pop" audible? I think you could be on to something here; however I can hear no misses at idle and it feels smooth as glass.

It is easy to hear on a 4 cyl, more difficult to hear on a 6. I would richen it up just to be sure.
You should also go through your ignition system, checking the components to make sure they are in perfect condition.