I”ve been troubled by a turbo lately. And being a gearhead in good standing, I’ve been able to deduce and diagnose that the problem probably isn’t the turbo, but the little actuator that opens and closes the air intake to it… Yup, it’s a Variable Venturi Turbo (VVT).

This troublesome turbo first came to my attention last humid summer when my VW TDI lost half it’s power after sitting in my very humid shop for a month. Rather than panicking and letting the not so local VW dealer throw $2000 worth of new turbo at the problem, I hooked up the VAG-COM diagnostic tester and quired the gurus over at http://www.tdiclub.com. The verdict was that the aging vacuum actuator for the VNT had rusted and wouldn’t open, causing the TDI engine’s brain to panic and cut fuel flow and power in what is referred to as “limp mode”. Repeated applications of a buck or so worth of penetrating oil freed the actuator and my TDI soon had it’s full 90 horses back.

My last post was about fuel problems, but now I’m not sure if the problem was fuel. Once last year and three times this year I’ve seen a dramatic loss of power as the fuel tank reached half empty, cured by filling the tank with diesel fuel from another source. But after a repeat of the half empty power loss wensday, I refueled and all was well… for about 10 miles. I was then stuck in the slow lane at J.B. Hunt pace for the hundred hilly miles to Birmingham. Stopped for supper and searched over @www.tdiclub.com, and came up with an alternate hypothesis- Maybe the actuator was screwing up again and triggering limp mode? Had another hundred miles to cover, so I resolved to go lighter on the throttle to avoid triggering another “limp mode”. Worked for about 80 miles until I gave it full throttle at only 2500 RPM to pass a slow truck. But this time, it finally turned on a Check Engine Light. Got a room for the night, then dug out the VAG-COM and plugged it in… code P0234, excessive turbo boost! A quick search suggested the problem was the actuator again, except this time it was sticking wide open. Knowing further damage was unlikely and knowing better than to tear apart a running car on the road, I kept to less than half throttle and kept the revs up on thursday with no more reversions to “limp mode” and the CEL even went out. Of course, by then I was in the flat Florida and there weren’t any hills to accelerate up at 70 MPH.

Now if I’d dragged this dieselcar to a dealer and paid a couple thousand dollars a pop for them to throw new turbos at it, I’d be justifably peeved. That’s why historicly most turbo’d vehicles have been sold to gearheads like hot rodders and truckers who understand them and can properly care for them… It’s SOP to idle a turbo’d engine for a bit after a hard workout to insure that oil is still reaching the turbo’s bearings as the turbo takes a minute or more to spin down. Blown turbos are expensive- even the car ones start at around a thousand bucks, and a blown turbo’s shrapnel can be blown right into the engine and destroy it too.

So it’s with some suspicion I note that the Chevy division of new GM is equipping most of it’s high volume compact model, the Cruise, with a turbo’d tiny 1.4 liter gas engine. In fact, they’ve made it damn difficult to buy a Cruze without a turbo- All but the price leader stripper models that are seldom stocked by dealers come with the turbo’d engine standard.

We are about to see what happens when a fragile high tech turbo is put in the hands of millions of mainstream drivers who probably don’t even know it’s there. Yup, the folks who never read the small print in the owners manual that might tell them to idle the engine for a minute or so before they shut it off. And in today’s anti-idling environment, would GM even dare recommend selective idling? Fat chance.

So a few years from now when there’s a million or more turbo’d Cruzes on the road, will Cruze turbos be grenading and taking engines with them? Then throw in the mix the traditional low resale value of GM products… Replacing the turbo alone on a 100,000+ mile Cruze will probably cost more than the car is worth.

Could the Cruze, thanks to it’s mass market turbo, be GM’s 21st century Vega? I hope not… The seeds of old GM’s bankruptcy were lain when angry Vega owners traded them for Toyotas, Hondas, etc.