Turbo now running rich after sitting for 10 days

stevepatfred · stevepatfred's Garage

Hi folks. So this one has me stumped. You may recall I was talking in a thread a few weeks back about running lean under boost, and determined I would need an adjustable WUR and solenoid.

Well after that I went away on business for 12 days, parked the car in spec, great idle, smoothe hard pull, just a little lean at very high RPMs.

Came back, took the car out, and it was immediately extremely RICH, at idle and all through the rev range, RPM at idle had jumped to 1500 and on boost AFR in the 9’s (was previously 11.5-12. Tried adjusting mixture and idle and it’s all out of spec. Idle now 13.5-14 and on boost still in the 9’s, and bucking.

What could have changed? The car was in a dark garage untouched. Could it be an air leak? Or WUR? I’m stumped, and a little frustrated to be honest. Engine is 500 miles into a complete rebuild, every line and hose changed, WUR rebuilt also. At thoughts??

T77911S · 09-23-2022, 03:04 AM

an air leak on the pressure WILL make it run rich. especially under boost.
dont think it will effect idle.

check the pressures, CP and system.

loss of power to the WUR

stevepatfred · stevepatfred's Garage

I will check pressures when I get some time. Just a thought could it be the frequency valve acting up? The o2 sensor is disconnected but if the frequency valve fluctuates from 50% it would randomly make it rich correct? Just a thought as that’s one of the only things not replaced. I’d be surprised if a rebuilt WUR failed after 500 miles.

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mark houghton · 09-23-2022, 10:27 AM

What T77911S said.
Per your freq valve question, if it stopped working (such as being unplugged or otherwise a loss of power to it) then you would see very lean conditions.
My bet is on an air leak at one of the intercooler o ring seals. Would really show up when on boost when the ring further deforms.

stevepatfred · stevepatfred's Garage

I have a freshly installed turbo Kraft long neck inter cooler so O-rings shouldn’t be a problem. You’re right though it does seem like a boost leak. With that said would a boost leak Make the idle AFR rich? The car went rich in all areas, not just boost. My thought with the frequency valve is it is inconsistent, ie giving a richen signal.

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flightlead404 · flightlead404's Garage

A boost leak would not make it rich at idle. Under boost, with the intake at higher than ambient, you have metered air being pushed out of the system which means there's more fuel per unit mass of air than expected - rich

If its not on boost the intake is at lower than ambient pressure, the air comes in. So you have unmetered air entering the system making it lean.

stevepatfred · stevepatfred's Garage

Ok, so it’s rich all across the board, idle, light throttle, boost. Which to me would indicate WUR, or something else. And the fact that it happened out of the blue after sitting for 10 days had me suspicious of the frequency valve. Thanks for the help. I think I’ll test the dwell and fuel pressure at the WUR and go from there

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T77911S · 09-23-2022, 04:53 PM

so its NOT rich but lean

the FV usually either works or it doesnt. they rarely fail.
make sure it is vibrating.
on the 911 its powered by fuse 18, i assume the same on the 930 but just a guess.

stevepatfred · stevepatfred's Garage

Sorry I miss-typed, it’s rich, very rich, idle was down in the 11’s on boost around 9’s after having parked it with very reasonable AFR’s

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Tonger · 09-24-2022, 05:22 AM

Check the power to the WUR and the RPM switch (if installed) with a voltmeter - should read ~12v between the two leads when the car is running.

The WUR gets power from the red fuel pump relay which can go bad. When the red relay fails, I believe it is possible for the fuel pump to have power while the WUR does not. The effect is even worse when the RPM switch power leads are installed piggyback on the WUR power leads resulting in no power to the RPM switch either and an instantly very rich situation.

This happened to me when the red relay went bad, fuel pump still operated and car was very rich. It went from well in tune to way out in the manner that you've described. To me, it is unlikely that there was some drastic change in the internal positioning of the diaphragm of the adjustable wur - sounds more likely to be electrical in nature.

stevepatfred · stevepatfred's Garage

Tonger you got it, checked power to WUR, nothing. Replaced relays with known good, still nothing, noticed front fuel pump making noise, checked fuses and a fuse that the pump had been wired in to bad molten but not blown, replaced, pump was quiet and car went super lean…reset the idle AFR and everything is back in spec!

Glad I found the problem, now to find out why that happened. I assume something is creating too much current but not enough to blow the fuse… these are Chinese fuses, could they be the issue?

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T77911S · 09-25-2022, 03:10 AM

i said that in post #2 !!!!!

DaytonaCoupe66 · 09-25-2022, 04:11 AM

[QUOTE=stevepatfred;11805970]Tonger you got it, checked power to WUR, nothing. Replaced relays with known good, still nothing, noticed front fuel pump making noise, checked fuses and a fuse that the pump had been wired in to bad molten but not blown, replaced, pump was quiet and car went super lean…reset the idle AFR and everything is back in spec!

Glad I found the problem, now to find out why that happened. I assume something is creating too much current but not enough to blow the fuse… these are Chinese fuses, could they be the issue?

Sent from my iPad using Tapatalk[/QUOTE

"....these are Chinese fuses, could they be the issue?.."

I'm not sure I'd automatically default to defect based on an item being made in China. It's getting tricky to find electrical parts that are not fabbed in that part of the world. I ordered a relay directly from P after reading bad reviews on the Chinese made stuff and paid 4X the price for an item that carries the P branding and is 'Made in China". Poor quality goods come out of North America too.

stevepatfred · stevepatfred's Garage

T77911S yes you did, I missed it in your post, thanks for the suggestion!

Re the fuses and my made in china comment it was more directed at the fact they are now made of plastic, I guess ceramic is impossible to get now.I may pull the trigger on a blade fuse setup to eliminate the problem. I’ve been having a bit of trouble with this type of stuff. Thanks again everyone.

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Tonger · 09-25-2022, 06:10 PM

If you choose to change over to a blade type fuse panel, I highly recommend the Adapt Motorsports panel. It has built in headlight relays and the openings for the wires are large enough to accommodate the ferrules which simplifies installation. The fuse panel from Classic Retrofit has openings that are too small to accept some of the larger wire bundles requiring a lot more work. I will be converting my 930 over as well.

https://forums.pelicanparts.com/porsche-911-technical-forum/1103755-adapt-motorsports-mini-blade-fuse-panel-g-bodies-review.html