Whenever I go WOT and go to redline on the 924S it spits out black smoke. I have replaced the spark plugs, Cat Converter, and the O2 Sensor. What else could be wrong? There is also a misfire at about 2900-3000 rpm. The vacum gauge always reads below 20 mpg whenever the gas pedal is pressed down.

 

Maybe the AFM adjustments a little rich?

 

How do you change that? I don't want to have my cat burned out right away from running too rich.

 

You would want to have someone who knows how to adjust it (smog tech) do the job. It only takes a few minutes after you remove the black cover on top of the AFM. It helps to have an exhaust gas analyzer (or smog machine) while you are doing the adjustment.

 

So I need to get this on a dyno or what? Is there any way I could do this myself?

 

Anyone?

 

fuel pressure regulator. Change it, i bet it solves most of the problem...it did for me.

 

Is there a for sure way of checking the fuel pressure regulator? Would hooking up a fuel pressure gauge to the fuel rail something like that help to diagnose if it is the fuel regulator?

 

Bump

 

I don't beleive it's under the black cover... My Porsche tech told me (as I'm having the same issue) it's next to the black cover, it's a little round circle that is flush with the top. the adjustment screw is under that. He told me to drill into it, put in a reverse-threaded bolt extractor, tighten it down, then yank the f*cker straight up. Under there will be an allen screw which is your adjustment.

the only reason I've not done this yet, is one of the PO's I'm geussing did this and f*cked with it, and that's why it's running rich...and of course, they had to put the plug back in making it difficult to get out as it spins when I put the bolt extractor in. Next trick in the book (also recommended by my tech) super glue a bolt to the plug, and yank it out with a pair of vice grips.

 

That is only the idle air adjustment screw. The main one is under the black cover for EVERYTHING other than idle. It is covered under a METAL cap for a reason from the factory. Black smoke at WOT hardly seems like something to do with idle. Some people think its an idle screw. You will have to disconnect the oxygen sensor and adjust in different rpms. Most people don't know how to adjust it properly by ear and just screw it up. Even Porche techs for any other porsche (not 944) don't know much about the 944 and I have seen many of our cars screwed up by these same techs. Its worth taking it to someone who knows and pay $30 (I know a guy in Harbor City-not a porsche mechanic but knows our cars inside out and a former smog technician) and get it done right.

 

What if I got on the dyno myself and tuned the air fuel that way? I don't know anyone really who could do that around this area. I will call around to see if anyone knows. Is there a way to see if the FPR is bad so I can rule that out or change it to see if thats the problem. If I don't have to mess with the afm I would be very happy.

 

Most competent smog technician will know how to adjust the AFM since all e30 3 series bmws has similar AFMs and many have been adjusted to pass smog. I doubt you will be able to "borrow" a dyno since they cost around $30-40k with lots of possibility of injury - liability for the shop. Also, I am not sure whether you know how to use the tail probe reading at the exhaust gas analyzer to diagnose how to adjust the AFM. I had to have 4 of my cars adjusted during a smog check and its the only thing I needed to do to pass smog and get the car running properly. The only other time was when the NOx was too high and a new cat was needed. You can choose to spend money to buy parts you don't need, but before I change the FPR, I would get a fuel pressure tester to make sure the fuel pressure is out of spec first.

 

Alright this is an update. I have replaced the FPR and it did help a little but still shoots out black smoke and I can still smell the raw gas when flooring the car. I also tested the DME temp. sensor the readings were 1.24k ohms when cold and 0.31kohms when warm. What else could be causing this.

 

"Alright this is an update. I have replaced the FPR and it did help a little but still shoots out black smoke and I can still smell the raw gas when flooring the car. I also tested the DME temp. sensor the readings were 1.24k ohms when cold and 0.31kohms when warm. What else could be causing this."



DO WHAT Legoland951 wrote!!!!!!!!!!!!!!!!!!!!!