2001 tt Missing at 4000rpm

[turbo4 me]

Hi Guys,

New owner here; back in July I bought a completely stock 2001 TT, 21,000 miles and in great shape. The prior owner put 7000 miles on it in 7 years, so suffice to say it has been a garage queen. I don't plan to mod or race the car but I do like to run it up to 100 occaisionally just for thrill of the pull. This is my fourth 911 but first turbo.

Last week the car developed a miss; I first noticed it in second gear at about 4000 rpm. Car continued to pull but with a lot of hesitation. Third gear was even worse.

Based on posts in this forum and some others, I have checked the MAF (voltage test was good but I cleaned it anyway). That had no impact so I changed the plugs. The original plugs were in the car and they were not terrible but showed some evidence of running hot.

New Bosch plugs really made no difference. If anything it seems like the problem is more random- one time it pulled great in second, then started missing in third. The next time it missed in second.

Also should mention that the problem occurs at WOT and at part throttle; above 4000 if I nail it, it is like hitting a wall. Boost goes to 0.6 or 0.7 but it just doesn't pull.

Any suggestions about what to check next would be appreciated.

Thx

[turbo4 me]

Remembered one other symptom- this afternoon during test drive it threw a CEL and I had 4 codes: 0300, 0306, 0305, and 0304. Multiple misfires on cylinders 6,5 and 4.

[Loren]

:welcome:

Those misfires are all on one bank (bank 2) which would make the MAF doubtful as the cause (it would affect both banks).

I assume you have made sure there are no air leaks?

Do you have any other faults (like 1325)? If so the cam adjuster maybe bad or the holding bracket on that side may have broken.

[turbo4 me]

Hi Loren,

By the way, I intend to become a contributor by the weekend. I have to fly out at 6:00 am tommorow to go get a car in New York for my wife but I will be back online Saturday.

No other faults or CELs. I haven't purchased the Durametric software but probably need to do that shortly.

I thought about air leaks due to the randomness of the problem- bank 2 is the right side bank, correct? I assume if I had a boost leak my boost would be all over the place, and doesn't seem to be the case.

Thanks

[Loren]

Correct bank 2 would be the right side as you sit in the car.

Most of the boost leaks I have seen result in huge power losses - but it would not hurt to check the hoses and clamps.

[Sunnyside]

Hi and welcome.

You could do with checking your fuel pressure. It comes to bank 1 injectors first then crosses to bank 2.

If your fuel pressure is dropping bank 2 will be the first to show signs..

When did you last have your pump checked, there is a U pipe on the pump that splits. Starts of small reducing pressure on wot but will eventually split fully. This will cause the car to crank over then splutter but not start.

Of course its just an idea but is worth checking your fuel pressure/delivery and pump U pipe.

[turbo4 me]

Thanks for the idea Sunnyside- will be back working on the car first of the week.

[turbo4 me]

Just to close the loop on this, after replacing plugs and coilpacks, there was still no improvement; if anything it seemed to be getting worse.

I was about to surrender and take it to the shop but I found a post on another website that suggested unplugging the MAF and driving the car to verify MAF operation.

With the MAF unplugged, the car ran like a rocket. Replaced the MAF and problem solved.

So the lesson I learned is that a defective MAF may pass the Basic voltage test.

[jsmith996tt]

Congratulations on your repair/fix. Like Loren, I would have never suspected the MAF, since all the codes were on bank 2. I guess now, whenever I have a miss I will unplug the MAF and see how she runs.

Joel

[Sunnyside]

Congratulations on your repair/fix. Like Loren, I would have never suspected the MAF, since all the codes were on bank 2. I guess now, whenever I have a miss I will unplug the MAF and see how she runs.

Joel

I too am taken aback by this as the fault was only on bank 2. Very suprising.

[700Turbo]

Very random but glad its fixed! i still have similar issues with mine, replaced all plugs / coils AND the maf but no joy :( im putting it down to catless exhaust now and that my tune might need tweaking, fingers crossed