Smokey, misfiring and mental acceleration..... - Alfa Romeo Forum
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Smokey, misfiring and mental acceleration.....

Hey folks,

I just wanted to share my experience, in the hope that it may save some time for other Diesel owners!

My car has been showing some really strange behavior over the last 6-9 months or so. Some of the symptoms were:
  • Flat spot under gental acceleration when hitting about 2500 RPM (like a misfire)
  • Excessive smoking under really heavy acceleration
  • Really sudden and dramatic acceleration when the foot was planted at about 2000rpm. So hard the clutch was slipping at times!
  • Slightly rough idle
  • Best of all was the whistle when pulling away in first gear gentle. Kinda like a dump valve

So I thought it was the MAF and went and replaced it. No difference. Did an ECU reset. No difference. I checked the bottom and top turbo hoses but they were fine. I cleaned the EGR but the difference was minimal.

So yesterday I was looking at the actuator that controls the vanes in the turbo. I followed the small pipe back up from it, around the fans, and into a device at the top of the rad. From here there was a looped pipe across the gap to the top of the engine. Low and behold it was split at the back (out of sight!!) right where it joins to the metal pipe it connects to.

I replaced the split pipe and the car is driving like it never has before!! I don't know how long this was split for but I never remember the turbo being so refined.

Basically what was happening (from my logic) was that the vanes were being left producing maximum boost all the time as the vacuum wasn't working correctly. Hence the dumping of excess air pressure and the whistle at low revs and the dramatic acceleration when planting my foot. The turbo now comes in A LOT smoother and more controlled. Also my boost gauge now returns to zero when I take my foot off the gas when cruising and I can see the pressure build up only when required.

It is like a new car....... at 185,500 miles!!!
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Good job I'll remember that if miner ever behaves like that

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yep same for me! 3M of silicone pipe sorted mine. when I get around to it I want to replace them all.....
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acceleration , mental , misfiring , smokey

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