Quote:
Originally Posted by john walker's workshop
See if the vacuum hoses attached to the pressure reg and the damper have fuel in them, as previously mentioned. They are there to route fuel to the intake in case a diaphram leaks. You can attach a longer hose to each nipple and run the engine to see.
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John... I'll do that.
Quote:
Originally Posted by Techno Duck
The puzzling thing is your saying bad MPG, but your data log looks like its running lean during city driving and normal at steady cruise.
Your saying no soot on the tailpipe or bumper so the only other place for it to go is in your oil. How many miles are we talking since this has been going on? Oil may smell like fuel if its bad enough, or send it in to be tested. The low tech way is to compare viscosity with a new sample of the same oil. Put a small amount on a piece of glass and hold it at an angle, both samples should run the same amount over time. Look up lube oil viscosity race test to see what i mean.
With the data log you posted, the reason i question the air flow meter is the test you did only checks the carbon track for wear. If the carbon track is worn, you will experience bucking or hesitation when accelerating.
What you cannot test on the air flow meter is how far the barn door is opening at a set engine load. This is what influences your air fuel ratio at partial throttle conditions. Adjusting the clock spring changes the tension on the door. Less tension on spring means the door opens further than normal, so it will run richer. More tension on spring means the door opens less, so leaner mixture. The clock spring can really only be set using a flow bench and to my knowledge ive never seen official numbers on where to set it at posted. The clock spring in the AFM never needs to be adjusted, unless you know the full history of your AFM i would still question it.
More info on the AFM and the clock spring;
https://forums.pelicanparts.com/porsche-911-technical-forum/835870-afm-mixture-am-i-lean.html
https://forums.pelicanparts.com/porsche-911-technical-forum/1105174-air-fuel-meter-adjusting-screw.html |
Jon... There's indeed a conflict between the city fuel guzzle according to the run & pump fill results (together with what I see when looking at the fuel gauge)---and then wideband data NOT showing any out of place guzzling. Wideband, as I've mentioned, has been tested and parts replaced to prove it being faulty. But couldn't make that happen no matter what was done. Conclusion... guzzle exists and wideband is accurately not showing where/when the fuel is being guzzled. Simple answer: fuel is leaking at a rate of 1/2 a tank per 200 city miles. That's not happening---I've checked and rechecked given this being an obvious conclusion. This guzzle & wideband conflict, I thought there was a clue in this but found nothing. Instead, it's a head-spin that leads away from from getting on with hunting down the solution.
Sweep... acceleration, easy or slammed WO, is without a moment of hesitation.
Links... I've not yet looked at them but will. Thanks.
Sal advised me on adjusting the position of the sweep arm. Am not going to do anything now with either the spring tension or arm until I know exactly what I'm doing. I did adjust the spring tension very early in this expedition but returned it to its original position. This was done prior to having the wideband installed so don't have any data relative to that adjustment. Now, with the wideband, it would be interesting to see what comes of any AFM adjustments.
Based on everyone's input to date...
Hit list:
- Vacuum line connected to dampener - check for fuel in line.
- Learn Motronic in order to intelligently adjust AFM - book ordered.
- Culpables = ECU - although tested and "no faults" found, this unit was not installed when engine was delivering 18 city. Coil - Blaster, although specs as promoted match original Bosch coil specs, Blaster was not with engine when it did 18 city. Undecided how to attend these items.
- Intelligently adjust AFM spring tension and log wideband results for each move.
- AFM - Look into Bavarian Restoration for AFM resto - email sent - 5.9.25 response = $365 return shipped domestic. 45 day turnaround ("lead time"). Greg is founder/owner. No retail shop. He does this part time at home.
Source notes on dampener if needed - tested 5.8.25, not needed.
Pelican - $665
Adapt in Switzerland - $322 - uses Bosch module rather than vacuum connection
Amazon - $50 - China
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