Surging when cold?????????

[john 928]

Im finally getting close to getting her on the road and now another issue. i took the wur apart and cleaned it out and put it back on and now the car dont stay running when cold. it starts and surges and after a few minutes of surging it then starts to run. it looks like the wur is not working after taking it apart.

any suggestions

[rjm65]

Try leaning the mixture slightly, surging at cold idle generally happens when the mixture is too rich. Sometimes all it takes is 1/8 or less of a turn on the mixture screw.

Buy/Borrow a set of CIS fuel pressure gauges, it's pretty much impossible to get a CIS car dialed in without confirming the fuel pressures are within spec. The first thing you really want to do, especially after taking the WUR apart, is to make sure the system pressure, cold control pressure, and warm control pressure are where they should be.

If you need a primer on how the WUR functions, start here:

Porsche 928 Forums dot com - View topic - CIS Warm Up Regulator Made Simple

[JK McDonald]

Hey John, rjm65 is right - the only way to straighten out almost any CIS fuel system issue without a gauge kit is by guess and by golly. They are not expensive - especially when compared to burning up several tanks of gas while you tweak at it or taking her into a garage.

Once you're plumbed into the WUR pressure control line you will easily be able to see what's actually happening as your engine goes through the warmup cycle. The best part I think is that you'll have the peace of mind of knowing that you've set your car up for the best possible power and economy.

Good Luck, Michael

[john 928]

Is the pressure gauge something that is porsche specific or can i pick up one for any car.
theres a harbor freight real close to me. Do you think thats something they will have.

[JK McDonald]

Hey John, The gauge kit everyone uses to troubleshoot their CIS cars is generic - Harbor Freight and JC Whitney both have a nice setup which includes the pressure gauge, valving manifold, hoses and a whole bunch of brass couplers/adapters/fittings.

Perhaps there is also someone near by who has gone through their CIS fuel system and can give some hands on help. From your symptoms - it sounds like the warm up regulator is the defective culprit and may just need an adjustment.

The WUR can be easily tweaked to better control the warmup and run fuel pressures. There are several good write-ups within the Pelican Parts site on how this is done. Check both the 911 and 928 technical posts - since the procedure is the same.

Good Luck, Michael

[john 928]

im going to pick up a kit today and check my fuel pressure to see whats going on .
Im just going to go buy one i have porsche in my blood and this wont be the only one i will own.

[rjm65]

Originally Posted by john 928

im going to pick up a kit today and check my fuel pressure to see whats going on .
Im just going to go buy one i have porsche in my blood and this wont be the only one i will own.

Make sure the gauge kit states it works with Bosch CIS systems. I'm not sure if the Harbor Freight set has all the appropriate adapters.

Here's what the correct kit looks like:
CIS, aka Kjet, 101

[john 928]

is that mixture screw the big one in front of the throttle chamber

[rjm65]

Big screw in the front adjusts idle speed, mixture adjustment is with a long allen wrench through the access hole in the front middle of the airbox.

MPDANO has a YouTube video on CIS injectors, fast forward to position 7:30 to get to the fuel mixture adjustment part.

Porsche 928 CIS Injector Changeout - YouTube

[SanDiego928]

Great video, very usefull. I really like your car MPDano.

[MPDano]

Originally Posted by john 928

im going to pick up a kit today and check my fuel pressure to see whats going on .
Im just going to go buy one i have porsche in my blood and this wont be the only one i will own.

I have a good working wur from my euro. It may have a different number on it but it will work and it functions perfect. I replaced mine with one from 928 motorsports when i was troubleshooting. Ended up being my fuel disty. Make me an offer

[BoiseShark]

John, I'm not going to be of any help, but I just wanted you to know what I went through with the WUR.

I bought a brand new one and thought they had sent me one for an automatic so I had them send me another one and I would send original back.

My bad...both were correct for my car. So I am able to trouble shoot with both WURs and I have checked my fuel pressure and even have an in-line pressure gauge for peace-of-mind.

System pressure is 70 psi (5 bar) roughly
Cold control pressure starts out at about 2 bar and it is about 70 degrees here when I test
Warm control pressure climbs to about 3.8 bar

From what I can tell, everything checks out but I still have a rough idle when cold and it wants to stall if I don't babysit it. As soon as it reaches operating temperature it runs great. I start it up and it runs at about 1500 rpm for a second or two and then drops down to almost stalling for another couple of seconds and then comes back up to 1000 rpm and runs good for about a minute and then it falls to about 500 rpm and that is when I have to babysit it until it warms up.

both new WURs go through the range and act exactly the same.

Not sure. and as far as the mixture is concerned, it is running rich. I have a digital gauge like Dano and it is sitting at about 10 to 1. When it warms up, it sits at about 11 until I get on the gas and then it drops down to 10 again. I have tried to lean it out, but the car doesn't like it and begins to run really rough before I can get it to read 14.

Car will die before I can ever get it to 14 to 1.

I don't know if this helps, but if you experience the same thing...something else is going on.