bshaw

I have a 1992 968 coupe with about 5K on a rebuilt engine. On cold start it seem like it is getting very excessive amounts of gas. It fires right up but I have to immediately put my foot on the gas pedal, hold it to the floor and run it up to about 3K for a minute or so. It spits out huge amounts of black smoke and then after a minute or so it clears up. If I don't do this it will stall and not restart. Have to walk away then return in an hour or so and try again. I have replaced the temp sensor. No change.

Not sure if this is related but I also have a check engine light that goes on and off once the car gets warmed up. Code is 1223.

When the car warns up it runs great !!!

Any thoughts ??

flash968

you sure about that code? they should be 1-1-something

do you have a vacuum guage?

Shaw968

Yes the code is 1223

Yes we have a vacuum guage. What specifically should we do to look for this problem with the guage?

BruceWard

1 2 2 3 is intermittent oxygen regulation. 1 1 2 3 would be constant oxygen regulation. My guess is the code means that the DME is receiving strange readings from the MAF. Is there another 968 owner nearby that you could borrow a MAF from and see if it fixes the problem?

I have the full code list posted at http://www.clubstuttgart.net/showthread.php?t=319 if you do not have it.

flash968

the intermittent thing, which is why i asked, tends to make me think it is something that is loose, that is correcting itself when warm - i just wanted to make sure it was intermittent and not constant

the manual says that code could be due, in your case, to a leaky intake - the vacuum guage would tell you - failing that, grab yourself a can of carb cleaner, and when the engine is warm and will stay running, spray it around where the manifold meets the head - if your idle changes, you have found your problem

it also says to check fuel pressure and for leaky injector valves

RajDatta

Have a fire extinghuisher handy if you perform the above test. Not something I would recommend.
Your FPR would be my 1st guess. It should be at approx 3.5-3.8 bar at idle.
Raj

flash968

given your personal experience with such things, i understand the hesitation, and would have one too, but i have been doing this for decades, and have never had a problem, or even anything close to one - it is a pretty well known and trusted diagnostic technique, recommended to me and others by countless mechanics, and has been around for a lot longer than me - like anything like this, you have to be careful, but it really has not shown itself to be a risk

the one thing to be careful of is getting the cleaner on paint, rubber, or electrical - you have to use the plastic straw and focus the cleaner on the specific area intended to test, and squirt it directly on that area, and only for as long as it takes to determine whether or not the intake sucked any of it in and resulted in an idle change

why would the fpr not work when cold but work when warm?

i am thinking the problem is likely due to material expansion somewhere - my thoughts are that a seal is not good when cold, but then firms up when things warm up and expand - this would point me to intake leaks, or something along those lines - the black smoke and rich running also point in that direction

but, there are electronic controls involved here, and one of those could be telling the DME to run rich at the wrong time

i'd start with the basics - verify correct fuel volume, and good vacuum

968rz

When I was an auto tech I used to do that (Spray carb cleaner) all the time, using the straw helps direct the stream it to pin point to leak (if there is one). In 15 years I never had a fire (but dont spray it on the exhaust manifold)