early 944 smogging up the world

[blk924s]

Hi everyone My friend has an '84 944 that won't pass emissions at idle. CO and HC's are very high, several times their standards. Loaded, the car passes with the specs right were they should be. He has a new factory cat, new O2 sensor, and new spark plugs. The AFM has never been opened, but is original.

The car runs decently, and pulls strong vacuum at idle. So far i'm thinking it could be the AFM being worn out, the DME could have a fault, or mayber the throttle position sensor?? Any ideas of how to test these or other possible culprits for problems? Thanks

[hpservertech]

What are the actual numbers?

In most states you can take your receipts for the work that was done and if it's over a certain amount get an exemption. It's usually around $400. And from the sound of what's been done, he may be past that if he went with a factory cat.

If he is running rich it could be a vacuum leak, which is most likely.

[John_AZ]

Originally Posted by blk924s

Loaded, the car passes with the specs right were they should be.
The car runs decently, and pulls strong vacuum at idle. So far i'm thinking it could be the AFM being worn out, the DME could have a fault, or mayber the throttle position sensor?? Any ideas of how to test these or other possible culprits for problems? Thanks

"Loaded the car passes..... My first suggestion is the TPS and to check all items go to www.Clarks-Garage.com for instructions.

It could be as simple as dirt and corrosion at the plug ins. Clean with contact cleaner and put some diaelectric grease in female boots.

He may have a bad "new" O2 sensor. Did he get a Bosch or an inexpensive universal? When he put it in did he have to cut the wires? If he cut the wires, did he follow the "DO NOT SOLDER RULE"?
http://reviews.ebay.com/UNIVERSAL-OXYGEN-SENSOR-INSTALLATION-INSTRUCTIONS_W0QQugidZ10000000000991989

He may also be eligable for the waiver:
http://az.gov/webapp/portal/SiteSearch?sitehome=http%3A%2F%2Fwww.azdot.gov&sitename=Dept.+of+Transportation&returnlink=http%3A%2F%2Fwww.azdot.gov%2FMVD%2F&logo=http%3A%2F%2Fwww.azdot.gov%2Fimages%2Flogo99. gif&template=http%3A%2F%2Fwww.azdot.gov%2Findex_docs%2 FSearch_Index.asp&q=cache:uk2Lzd0-w38J:www.azdeq.gov/environ/air/vei/fail.html+waiver&access=p&output=xml_no_dtd&ie=UTF-8&client=azportal&site=azdot&proxystylesheet=azportal&oe=ISO-8859-1

GL Tucson

John_AZ
1988 924S + 1987 924S

[mistahsinclair]

Hi there,

This is an excerpt from a post I had made previously following some issues getting through emissions:

My problem was NOX, rather than HC, CO2. The problem your friend is having is the opposite of mine, but the solutions are the same (just using the reverse...make sense?).

The air bypass on the MAF (or AFM depending on how you like it) might be very telling. Mine was way out of spec on the negative side. Your friend could be way out on the positive end. This is tested via the O2 Sensor...see below.

Adjusting the FQS on the DME isn't the best idea in the world, but if you just want to get through emissions it can be tweaked, then tweaked back.

There's also some fuel additive you can use that, allegedy, is Garaunteed to Pass http://www.autobarn.net/ch05063.html


----------



The 3 things that made the world of difference for me likely would for you.

Adjust the DME (adjust it back after the test)
Adjust the air bypass on the MAF
Replace the cat

Unfortunately all 3 things were done at once, so I don't know which one makes the biggest difference, but I'll give you my thoughts on them all.

Adjust the DME

Actually, it's the FQS (Fuel Quality Switch) in the DME that you're adjusting.

http://frwilk.com/944dme/fqswitch.htm - this tells you about the FQS adjustments. I put mine in position 4, you would likely be looking to position 2.

http://www.geocities.com/motorcity/1760/dme.html - this tells you how to access it.

http://www.promaxmotorsport.com/fqs.htm - everything on one page.


Adjusting the Air Bypass on the MAF

With the car running you need to back probe the O2 Sensor to find out the voltage. Anything over 0.5v means you're running rich. Below 0.45v is running lean (mine was at 0.32v when we started).

On the 944 the by-pass is adjusted using a 4mm allen key to a bolt on the MAF.

http://frwilk.com/944dme/afm.htm - the bolt head can be seen on the first picture of this page, lower right corner. It is covered by default. The cover is removed by screwing into the top of the cover with a sheet metal screw (just a couple of threads into it), then removing gently with a set of pliers or vice grips.

http://frwilk.com/944dme/lambda.htm - This gives you the voltage it should be.

Turning the 4mm allen bolt counterclockwise (I recall) will lower the voltage you read at the MAF. Take it slow and let the reading stablize before continuing to adjust. The reading will also jump around a bit so you need to average it.


Catalytic Converter Replacement

I would pick up a universal cat, then take it to a muffler shop and have them install it. You should be able to get one and hae it put in for close to $100. Might be a little more, but shouldn't be much.

[nynor]

plugged air filter? this sounds like it is running very rich. not a vacuum leak. bad fuel pressure regulator?

[John_AZ]

Originally Posted by mistahsinclair

Hi there,

This is an excerpt from a post I had made previously following some issues getting through emissions:

My problem was NOX, rather than HC, CO2. The problem your friend is having is the opposite of mine, but the solutions are the same (just using the reverse...make sense?).

The air bypass on the MAF (or AFM depending on how you like it) might be very telling. Mine was way out of spec on the negative side. Your friend could be way out on the positive end. This is tested via the O2 Sensor...see below.

Adjusting the FQS on the DME isn't the best idea in the world, but if you just want to get through emissions it can be tweaked, then tweaked back.

There's also some fuel additive you can use that, allegedy, is Garaunteed to Pass http://www.autobarn.net/ch05063.html


----------



The 3 things that made the world of difference for me likely would for you.

Adjust the DME (adjust it back after the test)
Adjust the air bypass on the MAF
Replace the cat

Unfortunately all 3 things were done at once, so I don't know which one makes the biggest difference, but I'll give you my thoughts on them all.

Adjust the DME

Actually, it's the FQS (Fuel Quality Switch) in the DME that you're adjusting.

http://frwilk.com/944dme/fqswitch.htm - this tells you about the FQS adjustments. I put mine in position 4, you would likely be looking to position 2.

http://www.geocities.com/motorcity/1760/dme.html - this tells you how to access it.

http://www.promaxmotorsport.com/fqs.htm - everything on one page.


Adjusting the Air Bypass on the MAF

With the car running you need to back probe the O2 Sensor to find out the voltage. Anything over 0.5v means you're running rich. Below 0.45v is running lean (mine was at 0.32v when we started).

On the 944 the by-pass is adjusted using a 4mm allen key to a bolt on the MAF.

http://frwilk.com/944dme/afm.htm - the bolt head can be seen on the first picture of this page, lower right corner. It is covered by default. The cover is removed by screwing into the top of the cover with a sheet metal screw (just a couple of threads into it), then removing gently with a set of pliers or vice grips.

http://frwilk.com/944dme/lambda.htm - This gives you the voltage it should be.

Turning the 4mm allen bolt counterclockwise (I recall) will lower the voltage you read at the MAF. Take it slow and let the reading stablize before continuing to adjust. The reading will also jump around a bit so you need to average it.


Catalytic Converter Replacement

I would pick up a universal cat, then take it to a muffler shop and have them install it. You should be able to get one and hae it put in for close to $100. Might be a little more, but shouldn't be much.

This was most educational for me.
My experience with our cars is more subdued.
The owner did put in a new factory cat.
Like hp and Nynor, I have found it best to try the obvious before mucking with the computer settings and not having an exhaust analyzer to reset.
The can of CRC fuel system cleaner may be the best answer because it could be a fouled injector staying open with a chunk of dirt . "Loaded it passes...fails at idle"...

blk924s-a while back, I thought you worked at a import repair shop??
Nynor

GL
John_AZ

[blk924s]

The actual numbers are approximately 10.1% CO and 600ppm HC (from memory i dont have the results here).

Ill try the fuel aditive and test the TPS first off, and see if he used solder and what brand of sensor it was. I remember on my car the ceramic element in my new universal o2 sensor broke within a year of use.

Ill try the AFM screw next and then i guess the FQS after that. How will changing those settings affect the loaded portion of the test and the driveability of the car in the mean time?

I still work at the Porsche repair shop part time, but this is a friend who i'm helping out for free. that means no borrowing the exhaust gas analyzer and i'm also not asking my boss the guru any questions, since i've recently started a separate shop with an entirely different focus, but still i don't want him to worry i'm trying to beat his prices with HIS customer base. Which i'm not. So i'm relying on trusty old pelican parts, which has never failed me

Thanks for the excellent advice and the overwhelming amount of helpful links

[John_AZ]

Gabe,

Good luck on your new project and your friends car.
I know I am beating this to death but if the O2 sensor is not sending the correct signal to the DME, the DME reads lean and adds more fuel= fail emmissions. Make sure you check the plug in connection.

Pep Boys has the CRC for $6.99 on the top shelf.

GL
John_AZ

[KitCarlsonEMS]

Perhaps the AFM is not able to close all the way, happens if something jams it. The clearances are tight top and bottom. It is running very rich, possibly more than what the O2 feedback adjustment is capable of. Also check the vacuum hose on the fuel pressure regulator. If the hose is off or leaky, the fuel pressure is increased at resulting in more fuel. Normally the vacuum will significantly decease the fuel pressure at idle. Under load the fuel pressure might be more correct. This is in line with symptoms.