Rich Sandor

I've come to accept that my car is running WAY too rich. I'm only getting about 220miles to a tank of gas. That's in the city, and with no constant excessive high RPM launches.

I know I could play with the AFM, but I don't wanna lean out the car too rich, as I've heard Danno say that these cars run too lean in some RPMS ranges. I'm afriad of that. But my MPG is so bad that's i'm thinking about it.

I really want the MAP kit, will that totally change my MPG figures? For the worse or better?

Danno

Hmmm, the MAP upgrade really just removes some major restrictions in your intake and lets you flow more air at the same boost levels. Not sure how that would affect gas-mileage.

But the chip-mappings do make a significant impact on gas-mileage: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=18;t=002444" target="_blank">MAF Stuff.....AGAIN!!</a> (check out VinceG's gas-mileage comment).

1FastRedSC

You might want to check the potentiometer screw on the bottom of the DME (it's usually plugged off but once you unplug it it's a triagular socket potentiometer inside the dme). Some people richen out the car with that screw to get a little more hp since it's free. It can go from stock to +3% to +6% to -3%. If you turn the screw all the way back as if your loosening a screw, counter-clockwise i believe, then you'll return it to stock. If that doesn't work than you might have to play with the afm, even though it's intimidating, when altitude changes it must be adjusted. I have an n/a 944 that i moved from being sea level to 3900 feet above sea level, needless to say that it was running too rich when i got here.

ninefiveone

It would seem your gas usage points to a problem somewhere that you should address. I don't have any good tips on where you should start but is the car in good tune? Last time you changed plugs, wires, cap and rotor? Air filter? Perhaps run some techron through to clean the injectors a bit.

I'd start with the basics and diagnose why the car isn't running properly before tweaking DME settings or looking to aftermarket chips.

Rich Sandor

The car runs EXCELLENT. except it eats too much. The compression and leakdown numbers were nearly perfect 4 months ago. I don't understand why plugs and wires and rotors would contribute to excessive fuel consumption. I am inclined to believe, that somewhere, something is telling the car to use MORE gas.

I suspect it is just the DME screw, but we'll see, I'll go look at it today when I figure out where the DME is supposed to be!

However, is DO have a giant conical K&N airfilter installed directly on the AFM. (No flat screen airfilter + snout and filterbox)

Maybe too much air?

All your help and ideas are very very much appreciated!!!!

Thanks guys. keep the idea's comin'

Danno

If you have AutoThority chips, do not use any FQS position other than 0 (stock, fully counter-clockwise). They have some bizarre values for the other ones and I can't imagine any car actually running with those settings.

So Rich, how would you like to get 6mpg better gas-mileage? heh, heh... <img border="0" title="" alt="[Wink]" src="wink.gif" />

Waterguy

Yeah, check which chips you have in it. I know that I have aftermarket chips (not sure which ones), and I definitely run rich. As stated above, FQS may also be part of your problem. Run Chevron 92 or 94 octane ("with more Techron!") as your only fuel and it should keep your injectors clean. I just had mine cleaned and flow tested, and they were all nearly perfect at 103k miles.

Too much air would cause you to run lean, not rich, Rich (perfect name for topic), so I doubt that that is the problem.

The only cure for poor gas mileage in a 951 that I have found yet is to bolt a block of wood to the bottom of your gas pedal.....

Phil Harrison

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Rich Sandor:
<strong>The car runs EXCELLENT. except it eats too much. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">My 88 origionally had a similar appetite, I found the Oxygen sesnor was old & tired. Now I get 300 miles from a tank around town & 400 on a long journey at 65-75. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

Have you changed the Oxy sensor? If not you can check it by putting a digital voltmeter across it's terminals (while still attached to the DME), at idle with a warm engine you should see the voltage cycle between .1 & .9 volts. Get the generic Bosch replacemt (139xx) if it's not OK.

smkn951

this is just an observation from my last tinker with my car. i cut the cat and i got extra mileage from it (48 m) to a full tank. on average i get about 320 to a tank. but i'm gonna put the oem cat back this weekend.

Rich Sandor

oh yeah i forgot about the o2 sensor. I gotta check that too..

thanks guys!

but Danno I am gonna get the Map kit within a few months anyways.

jason952

I am having the same issue. I run autothority chips (Gurus soon I hope) and have not had problems with them. Lately I get ~320 per tank when 400 was the norm with mostly highway running. New o2 sensor, and I am about to do the rotor/dist/plugs. wires are recent. anything else I should look at while I'm in there. Thanks,

Jason

K27

O2 sensor, most likely place to start. just change it IMHO.

fast951

Things I would check:

- Fuel Pressure, you might have a bad fuel pressure regulator.
- O2 sensor
- Clean the contacts of the plug at the AFM & Wiring harness. Use electrical connector cleaner.
- The film inside the AFM might be dirty. Remove plastic cover and clean with Qtip & Cleaner (GENTLY) do not bend moving parts.
- Check your braking system for any drag (not likely). While at it make sure your tires are properly inflated.

Note: Most if not all aftermarket performance chips run richer than stock as they get the additional HP by increasing boost.
Before spending money on another chip, find and fix the problem you have.