996 turbo stuttering

I haven’t managed to drive my car for approximately 18 months - other than driving it a mile each way to the garage for MOT last year, that’s all it did. Mainly due to focusing my attention on another car for track days - Doh! I had it MOT’d again this month and decided I need to use it more, last weekend I took it for a spirited drive and it was fantastic. The next day it was booked in for a photo shoot (for a uni students project) which involved a drive around town at 30. On the way home I detoured so I could put my foot down again, it did not want to accelerate, struggled with low boost and stuttered and spluttered whenever I tried anything other than minimal acceleration, EML also came on. I assumed this was down to old fuel so filled up with some new stuff, got home and tried to read the fault code. My iCarsoft POR V2.0 found engine code faults but I wasn’t able to read them properly, it showed something about being unable to connect. I cleared the codes and left it for the week as I was working away. I took it out for a drive today with the same horrible symptoms. No EML on but I was able to read fault codes which showed: Passive/Sporadic Catalytic Converter Efficiency Bank 1 and Bank 2. I’ve just ordered a new fuel filter but not overly confident that will cure the fault. I’ve (literally - at the start of this paragraph) checked the last time the plugs and coils were replaced - 10 years ago! I can’t believe it’s that long. It’s clocked up less than 20,000 miles in that time - do we think these are the problem?

Fueling issue ? ️ Unless the Cat’s need a clean… But giving it a service would help as plugs that old might be causing a misfire

It is already booked in for a service at Bahnsport. I always thought spark plug life is on mileage rather than years but 10 years is a long time. Time flies! Would spark plugs go from producing perfectly fine engine performance one day to absolutely terrible drivability the very next?

They could, but most likely linked to something else if it is a spark plug problem. Like fuelling, ignition (coil packs) etc. A service is going to hopefully sort out your issues. Good luck!

I’ve just ordered a new set of plugs. Hopefully I’ll get chance to replace them next weekend before it goes in for a service.

Mine is doing something similar. When I put my foot down it splutters for a split second and then it’s fine. On the last service it had new plugs and coil packs but it’s going back in to get looked at next month. It did have some codes that were cleared at the last service and I’m guessing it probably will have some again

I've just thought that the codes relating to the cat are probably a long standing EML issue I've had since installing a stainless exhaust. Sometime it throws and EML and I reset and forget. I did buy some stand offs but haven't gotten round to fitting them. Might be a good time to do so when I'm replacing the plugs. It doesn't feel like a misfire to me. I had a misfire prior to replacing the plugs and coils and this feels different. Hopefully replacing the fuel filter will cure it as the fuel was very old.

Maybe O2 sensors? When you change the spark plugs, have a look at the coil packs. Ah, another "while you are in there", check the condition of the "valve lift solenoid bracket" They are probably ok, but it doesn't hurt to double check as you'll be in there anyway. Full details here : link

I just got home and started looking at replacing the fuel filter. I am currently thinking I need to lower the engine a little to gain access to the filter clamp. But while in there I noticed a hose which was very poorly connected and it wouldn’t surprise me if it would result in an air leak. Can anyone help identify the hose? It’s the one with an approximate 90 bend on it before pushing up to the white/cream fitting on a straight pipe just above and to the right of the fuel filter. The second photo kind of shows where the hose clamp was (I hadn’t noticed the poor connection at this point). Hose now fully home on the pipe with the clamp in the correct place.

Appears to be a turbo oil or breather line after Googling the PN of a hose it connects to further forward: 996 207 139 70

It's an air line of some description, I say that because when I've removed it nothing drips out... I don't know what it's for though...although certainly better to have it connected than not

I wonder if that’s what’s been causing the problem. Maybe I should go out for a drive before I do anything else.

So it’s neither the dodgy hose connection or the fuel filter causing the issue. Plugs and coil packs to be replaced tomorrow. I did replace the engine mounts though with 964 RS mounts and it’s an absolute revelation for the gear change. Feels much nicer in the car as well as there must be much less noise and vibration now.

White clip is the brake servo, should have a clip to retain it as it is push fit. The black second is the fuel return. (99% sure)

So yesterday I replaced the plugs and coil packs, the old ones I removed looked fine. No improvement at all, in fact while test driving afterwards it actually lost all power. I turned the ignition off, re-started and managed to get home. It cut out twice on the short journey back. The code reader provides P0103 Hot Film MAF Sensor; which is something I was actually considering may be the problem beforehand. Luckily I had a new MAF sensor so replaced that. No change. Car cuts out. Doesn’t like to come on boost. Hesitant and stuttering off boost. Could it be a bad earth?