924Board.org

Alex Roy · Posted: Wed Jan 15, 2003 7:19 am Post subject:

I have a 1980 931, and in my quest for debugging my hesitation, I took out the lambda control box, and just for kicks, I tried to start up the car......not only did it still start, but there is no hesitation when accelerating......but according to my air/fuel gauge, without the lambda box plugged in, it runs VERY lean at idle and when not under boost, but when under boost the mixture is just over stoche (spelling?.....a little rich, like it should be). When I plug the lambda back in, the car runs like crap, I have all kinds of hesitation when I try to accelerate etc.

Does any body have a good lambda control box they want to sell me....or maybe some ideas of what parts I should check/test?

Smoothie · Posted: Wed Jan 15, 2003 7:43 am Post subject:

Maybe you just need to adjust the air:fuel? I'd do that without the lambda box, then plug it back in and see what you get.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Paul · Posted: Wed Jan 15, 2003 9:21 am Post subject:

Or maybe its your oxygen sensor....

924martinirossi · Posted: Wed Jan 15, 2003 9:54 am Post subject:

I'm going to replace my WUR as the control pressure is the same as the fuel pressure. The reason my car runs crappy (like you all are describing) is that the second diaphram in the WUR which responds to engine load by sensing intake manifold pressure is shot. High manifold pressure from an open throttle or from turbocharger boost acts on the diaphragm and lowers control pressure. Lower control pressure allows more plunger lift and greater fuel flow for a richer mixture. Since the pressure on the control plunger is so great the car leans out and starts to backfire when accellerating or going up a hill. Yes, you can remove the shims to lover the system pressure. Each 0.1 mm shim changes pressure by 0.15 bar (2.2 psi) I removed two shims from mine and dropped down to 76 psi.

Micahel

Smoothie · Posted: Wed Jan 15, 2003 10:08 am Post subject:

Actually, it looks like you lowered the system pressure almost to pre-1980 924na specs. 931s run higher at 5.4 to 6.0 bar like Paul said on the previous page. 924na's run at 4.5-5.2 bar (65-75psi). The correct spec for 1980+ 924na's and 931's is on page 72 of the Haynes - "System pressure (test value) 5.4-6.0 - it should convert to something in the general area of 80-90psi.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Smoothie · Posted: Wed Jan 15, 2003 10:14 am Post subject:

924martinirossi - did you check with NAPA for a WUR? (Wondering if that price and/or application were wrong on their website. It seemed to good to be true.)
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Smoothie · Posted: Wed Jan 15, 2003 10:33 am Post subject:

Alex Roy - that's a good point about the o2 sensor. I was thinking check your air:fuel mixture because your gauge is reading low at idle, but it could just as easily be a bad o2 sensor feeding both the gauge and the lambda box wrong info. I just recently got a spare from Autozone - the Bosch universal o2 sensor - only $18.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

924martinirossi · Posted: Wed Jan 15, 2003 12:39 pm Post subject:

I checked with them and don't remember what it costs. The best deal I found is a rebuilder that repairs and sets the cold control pressure to specs then ships it back for $115 + shipping.

Michael

924RACR · Posted: Wed Jan 15, 2003 11:29 pm Post subject:

Michael - please post that rebuilder's contact info! Also, do they do fuel distributors??? I am still struggling through the FI in the '81 931, and being able to get parts rebuild for such prices would be a huge improvement!!!
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

924martinirossi · Posted: Thu Jan 16, 2003 3:57 am Post subject:

Is this for a 1981-82 Porsche 924? The correct Bosch part number for a warm up regulator is
0 438 140 091

These are available rebuilt for $115 plus $25 core charge (refundable)

Shipping to Seattle via ground is $5.90

Parts Order Line
503-244-AUDI
Monday-Friday, 9-6PM PST

Thank you for your parts inquiry
Scott

www.SJMAutotechnik.com

I'll go hunt down the Fuel dist info later.

Michael

924martinirossi · Posted: Thu Jan 16, 2003 3:58 am Post subject:

Vaughn;

Did you receive your tester from BMP yet and what is your control pressure?

Michael

924martinirossi · Posted: Thu Jan 16, 2003 4:07 am Post subject:

Alex;

This is the first time I have saw your face and this is me kissing the car good by at your brothers house

Michael

924RACR · Posted: Thu Jan 16, 2003 4:22 am Post subject:

No, actually, it was still on backorder. However my half-fast attempts previously to measure control pressure on the 931's have shown nothing conclusive - incorrect fittings and leakage prevented getting a good measure. FWIW the 82 runs good on boost, I think, but not so hot off boost. I took apart the WUR from the 81, and it seemed fine by visual inspection, but who knows. That car doesn't run at all.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

924martinirossi · Posted: Thu Jan 16, 2003 4:48 am Post subject:

You can always sent the WUR to me to test.

Michael

email off line if you want to.

Alex Roy · Posted: Fri Jan 17, 2003 5:12 am Post subject:

Michael-

That pic is great, I showed my girlfriend the full size one and she didn't quite understand what it was all about. I guess she just doesn't know how these cars seem to turn into a 2nd (or 3rd........) girlfriend.

I know that there is something up with the lambda box, when I first hooked up the a/f gauge, it showed all the way rich instantly, so I disconnected it all and used my VOM and found that the line to the oxs sensor was putting OUT ~8volts all the time (it is supposed to be receiving the signal from the sensor, not sending out voltage). After all that, I disconnected the lambda's OXS wire all together and used my new OXS sensor connected just to the gauge, that is how I am getting my readings now.

Sense I am seeing weird voltage out of the lambda's OXS wire, I am suspecting a bad lambda box.....but it doesn't seem that anybody has a spare they want to sell me.