85.5 hesitates

[my1st911]

My car runs relatively well, but i must say 2 things concern me. For one it seems under powered. I know some will say to get a turbo, and I can not agree more, but I feel like its really under powered. I accelerates and hesitates while doing so. My gas mileage really stinks too. My question is does the computer store codes. How do i go about testing. I think maybe I am running rich, but how can I tell. The AFM has been opened at some point by PO, so who knows. How do you guys determine if its running rich or lean.

[Techno Duck]

The computer does not store codes. Hesitation can be the wiper strip inside the AFM is worn out. You can check this by measuring the voltage through the AFM through the complete travel of the inner door. Check ClarksGarage for a how-to..

http://www.clarks-garage.com/shop-manual/elect-22.htm

There is no easy way to tell if the car is running rich. The correct ways to do it are using an 3 or 5 gas emission analyzer which any place that does state inspections should have or to install a wideband O2 sensor. The other method is to check the voltage from the O2 sensor on the car, but this can be difficult because its hard to get a clear # and the accuracy of your #'s is dependent on the condition of the O2 sensor. The not so accurate ways to check are black smoke from the exhaust on acceleration and at idle the exhaust will make your eyes want to water.

There are a few potential reasons for a car to run rich. Bad O2 sensor, bad DME temp sensor, mis adjusted CO adjustment screw on the AFM and faulty fuel pressure regulator are the most likely causes. A lean running car is usually a vacuum leak somewhere.

[phoenix_iii]

Use the SAME filling PUMP, and get your mpg... Bad mpg of 25 is way different than 15mpg... =)

[my1st911]

Originally Posted by Techno Duck

The computer does not store codes. Hesitation can be the wiper strip inside the AFM is worn out. You can check this by measuring the voltage through the AFM through the complete travel of the inner door. Check ClarksGarage for a how-to..

http://www.clarks-garage.com/shop-manual/elect-22.htm

There is no easy way to tell if the car is running rich. The correct ways to do it are using an 3 or 5 gas emission analyzer which any place that does state inspections should have or to install a wideband O2 sensor. The other method is to check the voltage from the O2 sensor on the car, but this can be difficult because its hard to get a clear # and the accuracy of your #'s is dependent on the condition of the O2 sensor. The not so accurate ways to check are black smoke from the exhaust on acceleration and at idle the exhaust will make your eyes want to water.

There are a few potential reasons for a car to run rich. Bad O2 sensor, bad DME temp sensor, mis adjusted CO adjustment screw on the AFM and faulty fuel pressure regulator are the most likely causes. A lean running car is usually a vacuum leak somewhere.

Thanks, thats all great info. I didnt realize that there was an adjustment screw on the AFM. I smelled the exhaust, and it stinks, and my eyes do water a bit. Thats why i was assuming rich. Its hard to tell MPG, because my odometer works when it wants too. The speedo always works, but I noticed one day that odometer wasnt moving. Then the next time I drove it, it moved. I work about 7 miles away, and I dont do very much casual driving, but I do fill up once a week with an average of 16 gallons. No black smoke either

[my1st911]

Originally Posted by phoenix_iii

Use the SAME filling PUMP, and get your mpg... Bad mpg of 25 is way different than 15mpg... =)

Hey phoenix, looks like your in my neck of the woods. I have a stupid question, and a bit embarrased to ask, but what does DE stard for. Is that driving experience. The people on these forums abbreviate alot, and sometimes I am scratching my head

[Techno Duck]

Drivers Ed, also known as HPDE.. High Performance Drivers Ed. Basically driving on a race track with a instructor.

[my1st911]

Originally Posted by Techno Duck

Drivers Ed, also known as HPDE.. High Performance Drivers Ed. Basically driving on a race track with a instructor.

Thats what I thought. Seems like fun, I'll have to get involved with that. So if I suspect I'm running rich, can i just adjust the AFM

[bud9344]

AFM is preset adjustment from the factory to get a correct Air/Fuel mixture the same as in Carb. (the Old Days).
I have been fooling around with the AFM for sometimes and my conclusion is the AFM can be adjusted. This was the set up I have on my 85.5 944, the car was running perfect before the accident and I haven't change anything on the AFM




On picture #2 the brown arrow is the adjustment to control the opening off the door the more tension on the door the less air it pass. And the blue arrow is the sweep to control the injector timing (how long it open) Rich/Lean.
The adjusment screw outside the black cover is just adjusting the amount off off unmeter air, by passing the meter.

Hope this info help

------------------------------------
Bud

[Techno Duck]

Originally Posted by my1st911

Thats what I thought. Seems like fun, I'll have to get involved with that. So if I suspect I'm running rich, can i just adjust the AFM

Personally i would not adjust the AFM without first testing the other things i mentioned in an earlier post (DME temp sensor, O2 sensor, FPR). These are usually the big 3 when trying to figure out why its running rich. I would adjust the AFM as a last resort.