Still have the Emission Blues...

fig911 · 01-31-2003, 09:36 AM

I can't get this thing to pass. I have a 1986 911 coupe. It has a stock engine and exhaust. In Missouri, you have to pass three catagories:
1st time tested:
Hydrocarbons: Pass = .8000 Mine: 3.0705

Carbon Monoxide: Pass=15.000 Mine: 12.3295

Oxides of Nitrogen: Pass=2.000 Mine: 3.1282

My mechanic says that he thinks the engine may have some sort of oil burning problem. He said it isn't all of the time, but enough to cause high readings. It doesn't seem to consume oil too much 1 quart every 1200 miles. I have changed the oxygen sensor @ $218 including install and he has adjusted it to try to "lean it out". Also put in a new temp sensor for the pcv valve.

Most recent test after new Oxygen sensor and adjustments:

Hydrocarbons: Pass = .8000 Mine: 4.4175

Carbon Monoxide: Pass=15.000 Mine: 14.8599

Oxides of Nitrogen: Pass=2.000 Mine: 3.88862

To get a waiver, I only have to show inprovement in the initial readings (and spend over $450). I have actually taken it to get tested about 4 times and never gotten better than the first time.

Help...Any suggestions would be greatly appreciated.

Mark

Rot 911 · 01-31-2003, 09:53 AM

Mark, you just can't "lean out" the 3.2 engine in your car. The DME actually controls the fuel mixture based on readings from the 02 sensor. However, in the DME control box, which is under the driver's seat, you will find a small dial that can be adjusted with a small screw driver. It has several settings that will lean/richen your fuel mixture. There has been a couple of threads on this in the past. So if you spend over $450 then will they give you the waiver? If not perhaps you can just drive out here to Jefferson City, borrow my home address, and register it here where we have no emissions testing!

gregk1 · 01-31-2003, 09:55 AM

I would consult John Walker on this one, I think he has a few tricks up his sleve That might help you.

Rot 911 · 10:10 AM

Mark here is another thought that popped into my head: A working O2 sensor AND head temp. sensor are required for the DME to function properly. If the head temp. sensor is bad ... the DME 'thinks' the engine isn't warmed up, and never goes into closed-loop, normal operational mode, and doesn't even use the O2 sensor data, which will leave you always running rich. Have you checked your head temp. sensor? The old style single terminal head temp sensor is the usual culprit. they don't ground well when they get old, causing intermittent jerking and dying. that's why they have been superceeded to the two terminal style. have you done that yet? then get on it. 1/2 hour job and it will probably fix it. To add to my previous comment on the DME, the Motronic DME control unit has an internal 8 position rotary switch that can be adjusted "to adapt fuel mixture and ignition timing for the quality of gasoline in the country of operation." I belive position 4 leans the mixture approx. 2-4%, position 0 is the default position. Position 1 and 2 richen the fuel mixture.

fig911 · 01-31-2003, 10:08 AM

Kurt,

I may take you up on the address borrowing idea if I can't get the pass or a waiver. To get a waiver now (new 2003 rule) you must spend at least $450 AND show imporvement from your first failed test.

I've got the $450 covered but can't seem to show improvement.

I did also have the temp sensor changed for a new one. He said it wasn't working properly.

Mark

Rot 911 · 01-31-2003, 10:12 AM

Did a quick search and also came up with this thread:

Wooooe there!
Hold on a sec.
YOU CAN adjust your fuel mixture and make the car run lean or rich!.
DO NOT unplug your O2 sensor to do this!.
You may be able to do a search on this otherwise the other guys will direct you more acurately, but I did it will my car about a year ago and had it running fine!.
Evidently the factory set the car running slightly rich, but it can be adjusted.
Trick is ... where is the screw?
Unfortunately I sold my car a year ago!!!

But I beleive the screw is under the air mixture box? the box that is aluminum and webbed (sounds crazy I know but am trying to picture the engine bay!)
Help me out someone!!!!!
Anyway, I think you screw the screw in all the way and then factory setting is 5 rotations out and optimum is 8-10 out.
But do not quote me on that!
These guys will confirm screw turns
Common Guys!
Regards
Ben

__________________
1971 911T Targa - twin plugged 2.7
2002 VW GTI 1.8T - daily driver
1999 Chevy Suburban - company car

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07-26-2002 07:45 PM

mskar
Member

Registered: Feb 2002
Location: Va Beach, VA
Posts: 53
The screw is on the airflow meter and is, afaik, for idle mixture adjustment only. By removing the large plastic cover on the meter, you can access a dial which sets the tension on the door, which will adjust your mixture throughout the range, not just at idle. My car (an 84 Euro graymarket conversion) had a previously removed plastic cover, which I reremoved to see what they had done. I turned the dial back to its original position (there was a worn spot) and my car has never run better, exhaust smells a bit richer but the difference is night and day especially at lower rpms. SteveW enlightened me to the purpose of the dial in a previous thread, I don't remember which way richens and which way tightens, but you can look up the thread for more info. Also, I completely agree with not making any adjustments to the airflow meter, disconnecting the o2 sensor etc unless you are sure you have everything else is working properly (plugs/wires/cap/rotor/no vacuum leaks, etc) If you're afm has not been previously opened, and everything is otherwise in tune, go with the autothority chip. My 2 cents

Rot 911 · 01-31-2003, 10:16 AM

And finally I know one way you can "cheat" and lean the mixture out. This is by creating a common problem on the 3.2 engine that usually creates a lean mixture problem that needs to be fixed. On older 3.2 engines the gaskets between the intake runners and the heads dry out, crack, etc. or the intake runner bolts loosen up and allow air to enter at that point. The DME does not correct for this problem. You could just loosen the bolts up on each runner a bit and thereby allow additional air to lean the mixture out. Then take the emissions test and tighten the bolts back up. Of course you still need to fix whatever is making you run rich in the first place as that is not a good thing to have.

Rot 911 · 02-19-2003, 11:23 AM

Mark, just curious, did you ever pass emissions testing?

john70t · 03:56 PM

Looking at the figures doesn't seem to make sense. To get a true reding you have to go into the testpipe before the CAT(which will clean up 1-3%CO and 50-200 PPM HC)
The most important, CO, will tell you the mixture. Yours is just about at the max, which would indicate you dont have an overall lean issue.
The second, HC's will be high on a lean misfire (the raw vapors go out the pipe) but low on a mixture that is only running a little bit rich.
The third, NOX, is only created above 2500deg- i.e. in a hot, lean mix, high compression engine under load. This is also high....so...

My guess would be you have a lean misfire in one or more of the cylinders which acounts for the high HCs and the high NOX.
Perhaps from an overtight valve or a clogged injector.

The Oxygen sensor (which is really only a fine tuner-the MAF and cyl temp doe the big calculations) is seeing this and the computer is trying to compensate by richening up all of them-thus the high CO.

stormcrow · stormcrow's Garage

Check your timing to see if it is set properly. Does the test require the engine to be at idle or higher rpm. If your timing is off this could be the cause of your problem.

Steve

"A Porsche does more then just go fast in a straight line"

pbs911 · pbs911's Garage

Braze the end of a fuel injector. That will cut emissions by 1/6th, more if you can find one cylinder that has high emissions than the others.

Adam · Adam's Garage

Quote:

Originally posted by Kurt V:
the Motronic DME control unit has an internal 8 position rotary switch that can be adjusted "to adapt fuel mixture and ignition timing for the quality of gasoline in the country of operation." I belive position 4 leans the mixture approx. 2-4%, position 0 is the default position. Position 1 and 2 richen the fuel mixture.

So, could I then adjust the DME on my '89 to enhance performance? I currently run it on 98 RON Premium fuel. I had never heard of this before.

What setting would you suggest for a RoW/Euro 3.2 ('89) that runs 98 RON fuel all the time? Fuel consumption is not an issue.

VincentVega · 02-19-2003, 07:39 PM

Havent done it in the porsche, yet, but if any other car I 've had failed I installed new plugs and ran a can of octane boost. It may sound cheap but it's always worked for me.

rick-l · 02-19-2003, 08:18 PM

Are you sure you have to spend $450 and show an improvement in Missouri? Better check the rules. I live in St Louis and thought you only had to spend $250 on related repairs and it didn't need to show an improvement. It was only the 1996 and newer (obdII) cars that had the waiver limit set at $450. The show an improvement and unlimited cost didn't kick in till 2005. Next test you go to take your receipts and get the pamphlet "My car failed now what do I do?". Fix your car but do it at your leisure.

slater · 02-19-2003, 08:43 PM

man i'm glad i live in a county without emissions testing!

FlaCarrera · 02-19-2003, 10:48 PM

Quick fix...move to Florida, land of Euro premufflers & after market SS exhausts. Sorry, couldn't resist.
Ted in So Fla
86 Carrera Targa

Dan Owens · 02-20-2003, 05:55 AM

I would think the mechanic would be able to tell you if his adjustment was correct or not if he's monitoring what he's doing when he adjusts the Air Flow Meter. If he isn't then I'd take it to a mechanic that does monitor the emissions during adjustment. I'd ask him what readings he's getting and what they mean. There shouldn't be any quessing here at all. the readings tell you what's happening and here the mis-adjustment should be at or the cause of it.

fig911 · 02-22-2003, 04:09 AM

rick-I

The new rules take place as of 2003. Since I didn't get my first test until Jan. of 2003, I have to qualify under the new rules. They state that if you car is like an '82 or newer, you have to spend at least $450 and show inporvement.

As it turns out, I got lucky...

I was able to take unlimited re-tests for 30 days and as I was getting close to the end of my free retesting peroid, I took it in and it did fairly well. I did show inprovmemnt in one area, but not all three as the rules state. The luck part was that the testing facility lost the origianal information for the first test I took. They had to print out some massive summary and try to figure out what numbers I had to beat. I knew all along but kept quite. They picked the wrong numbers and it looked like I showed improvement in all areas so they gave me a pass...hahahaha

I ran straight to the DMV and got my two year plates and so I have some time before I will need to deal with this again.

Thanks for all of the suggestions, I will probably need them in about 22 months.

Fig.