jagdhund

Ok so first a little background info. I bought my car 4 months ago in great condition and with complete service history. I have put 1,500 miles on it since and has run great with no signs of any issues until last friday. I had drove it about 40 miles to a friends house with no issues. I parked it in his drive way which was steeply uphill. It sat about 5 minutes and then I went to move it and it immediately started miss firing and dying. I let gravity pull it out of the drive way and let it sit on the level street about 10 minutes. Then it started up and ran with no issue. 4 hours later I started it and drove it about 5 miles and filled the gas tank, no issues. Then another 3 hours later drove it home 40 miles, no issue. Then it sat 2 days. I started it Monday morning and it ran fine for about half a block then it slowly got worse, made it to garage were I park my daily driver (about 3 miles) and stopped driving it. I checked the car again 10 hours later after work and same issue. Then again this morning, same issue. Then today after work did the first thing I could think of, spark plugs, and it made no difference.

Now to expand on the issue, when I start it, it cranks for longer than usual, then the tachometer jumps from 2000 to 500 rpms consistently at idle and the whole car shakes badly. If you rev it, it wont go above 4000 and it is much louder and harsher than normal. Then if you quickly let off of the gas it dies. When driving it it has very little power. Also the exhaust smell is very strong and seems like it is running rich. It doesn't seem to get better or worse as the engine warms up, but I'm also afraid I might damage it if I let it run too long in this condition.

As I said the first thing I tried was the spark plugs. The old ones were worn with some carbon build up but not horrible. I had a friend mention seafoam but I don't think that will do anything for this issue. some one else recommended changing the fuel filter, but I think the problem is more severe than that. I think there is an issue with the fuel injection system, maybe a sensor or something.

So before I start guessing, or spend a lot of money at a Porsche specialist repair shop, I was hoping the knowledgeable people on this forum might be able to point me in the right direction.

Thanks in advance for the help.

mel_t_vin

Could be a multitude of things...

I would start by checking vacuum connections downstream of the AFM for unwanted entry of un-metered air. Next, check the vacuum connections at the ICV, FPR, and FPD.

Other potential suspects, in no particular order: FPR, TPS, AFM, DME temp sensor...

931guru

Plug wires.

ramius665

Plug wires will cause the symptoms you're describing. For whatever reason the S2/968 plug wires are very expensive but a fellow 'Lister (Dougs951) had a very similar issue with his S2. It would crank for what seemed like an eternity before it caught and fired plus it had a misfire in the upper RPM range (above 4k IIRC). He replaced the plug wires and cured the issue.

Vacuum leaks should always be suspected as well, wouldn't hurt to double check all of the connections and the hoses.

joes

Cap, rotor, coil wire (it fires 4X more than the others) Fuel pressure.

mytrplseven

This sounds, to me, to be fuel delivery oriented, since it takes so long to start up. First the leak-down of fuel from the lines smacks of the check valve in the fuel pump. I'd also suspect the fuel filter. I think it would be prudent to just pull the fuel pump and filter, check the screen in the fuel tank for crud and look at the vacuum connections on the FPR and a possible failed FPR. Quick and easy, start with the FPR and work backwards to the fuel pump/tank area. Autozone also has a gauge set that you can borrow to do the entire fuel system checks for pressure, leak-down, etc.

thomasmryan

yeah, if your plugs where dry, that should point to a lack of fuel. See if you have spark and fuel pressure and take it from there. Could be something simple like a corroded wire at the fuel pump or the check valve is sticking. If you have good fuel pressure and a nice blue spark, start looking at electrical, your grounds and vacuum controls.

An engine slowly sputtering out and won't run over x rpm says starving for fuel to me...

mike77

I had very similar symptoms with my S2 recently. Turns out I had a pretty big fuel leak which resulted in fuel pouring down the street.

jagdhund

The plug wires are all fairly new (they were replaced in 2012), but I checked them all anyways, I checked for spark and they all seemed fine. I starting looking at the vacuum lines, didn't see any issues, but after I had unplugged the air flow meter and plugged it back in it started and ran fine, it was a little rough at idle still but no where near as bad as before, after a quick drive it idled better but the power seemed down, probably at about 90% of what it was before. I'm guessing the wire connection got lose, ill look at replacing the connector if this happens again. I'll try some more of your guys suggestions to try and get that other 10% back.

While I was looking at it I went ahead and changed the oil, and saw another issue.

Thanks for the help guys.