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Air:Fuel mixture problem

'87 951 with Air flow meter, dual port waste gate, open exhaust(track car). I'm having an extremely rich condition under load.
Under low load car is running in the 15:1 range. As soon as the throttle is open
Air fuel ratio drops past, 10:1, the rich range of wide band. At 10:1 car will run but not well. Continues going rich until car car won't run.
I have check output voltages from AFM and they are correct.
I'm leaning toward the DME as the culprit.
The car went from running great to this instantaneously.
Any ideas?
Old 10-14-2009, 03:26 AM
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All Spooled Up
 
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Ideas? You bet.

CRANK UP THE BOOST!
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>gray 89 951S - K27/8, MAF, 3" intake, 3" exhaust w/separate waste pipe, 55# inj, late cam; >red 87 924S - chip, K&N, punched-out cat&muffler >black 80 924 - (sold) >maroon 77 924 - auto (sold)
Old 10-14-2009, 05:33 AM
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All Spooled Up
 
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Hey, I just noticed that is your first post. Please don't take my "idea" too seriously. In theory, I suppose you could up the boost until you bottomed out at 11:1, or so. But if it decides revert back to the way it was, you would probably go too lean.

No realistic ideas, other than to say that you need to check fuel pressure readings under boost. If they are good, then it might something electrical. Have you checked the blink codes?

And by electrical, I mean that, if not the DME, than something feeding it a bogus signal - like a short, or an open, from a sensor (of ANY sort) to the DME's input pins.
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>gray 89 951S - K27/8, MAF, 3" intake, 3" exhaust w/separate waste pipe, 55# inj, late cam; >red 87 924S - chip, K&N, punched-out cat&muffler >black 80 924 - (sold) >maroon 77 924 - auto (sold)

Last edited by wild man; 10-14-2009 at 06:09 AM..
Old 10-14-2009, 05:55 AM
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Are you running stock chips? Check the operation of your TPS, DME temp sensor and verify the fuel pressure regulator and or damper has not completley blown by checking fuel pressure.
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Old 10-14-2009, 09:05 AM
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Running 16psi when car is running, can't get past 5psi now. Have to close throttle before going any further.
Weltmiester chips, adjustable fuel presure regulator (new) with gauge. New damper.
Car came with these chips, have been running the car 3+yrs.
When I say this happened instantaneously, I mean comin off of turn six at Road Atlanta pulling perfectly, coming off of turn seven car started doing this.
Again car has a wide band so there is no doupt it is going extremely rich.
Have checked TPS. I don't think the TPS would or could do this.
With the TPS disconnected the car runs rich but not llike this.

Last edited by Karl Schaefer; 10-14-2009 at 12:45 PM.. Reason: more info
Old 10-14-2009, 12:35 PM
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Rogue Tuning
 
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Check for boost leaks. Sounds to me like you have a significant integrity loss in your intake path. Maybe ripped a coupler or pushed a gasket.


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Old 10-14-2009, 12:49 PM
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Thanks, will check and get back.
Old 10-14-2009, 12:51 PM
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Had checked boost tubes and connections previously. Just rechecked, they look good.
What doesn't look good is how much of the #4 intake gasket I can see. The gasket is over 1/8" showing past the the intake flange.
Going to pull the intake...
Will let you know.
Old 10-14-2009, 01:54 PM
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Rogue Tuning
 
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Make a intake pressure tester; it will identify leaks easily:

Intake Pressure Tester


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Old 10-14-2009, 02:52 PM
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Intake is off, gasket looked deformed more than blown out.
Thanks for the link to the presure tester and your input.
Hopefully new gaskets will do the trick.
Old 10-14-2009, 03:00 PM
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Hi Karl. Hopefully you'll find your problem soon. Nice seeing you at BMW Octoberfest.
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Old 10-15-2009, 05:16 AM
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Hey Lawrence,
Good to hear from you.
Got the intake back on, still doing the same thing.
Going to pressure test boost side today.

Karl
Old 10-16-2009, 03:35 AM
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That sounds like a good idea. Probably will build one for myself.

Am installing new front rotors today. New ones with all the 'extra' metal are quite a bit heavier... Good luck with your car.
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Old 10-16-2009, 05:27 AM
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Check the couplers at the IC. The get cracked and broken badly on the underside.

Also check the hose coming out of the turbo on the back side.
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Old 10-16-2009, 06:33 AM
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Don't know how I missed this!
Removed hose from turbo to pipe and found a split in the hose close to two inches long. I think the trick is to remove the parts for thorough inspection.
Thanks for all of the help.

Karl
Old 10-16-2009, 10:39 AM
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A ruptured diaphram at the recirculating valve will also cause the same symptoms. I should have mentioned this but forgot.

Do you remember the spring settings of the flapper that you were adjusting earlier?
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Lawrence
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2011 528i
Old 10-16-2009, 11:20 AM
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Yeah, have the "gear" marked at original setting.
I added tension to lean car out at lower RPM's.
Completely different problem.
It was running really well before this latest problem.

There is a MAF in my future, just that due to my current situation can't justify!
Old 10-16-2009, 12:29 PM
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If it went from running great to running like crap, something blew off..

Every vacuum line becomes a boost line under boost, check every line. A hole the size of a pencil eraser can really mess up your day.

One of the intercooler pipe clamps is loose, or J-boot, or by-pass valve. Or just one of the lines blew off the intake, check them all.
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Old 10-16-2009, 08:29 PM
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Old 10-16-2009, 08:29 PM
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