Hi Brickboard Members,

It may be that the turbo on my 1990 740 turbo wagon with automatic transmission and nearly 208,000 mi. on the odometer is not boosting. Maybe this has been going on for months. I drive conservatively. The car drove recently from Wisconsin to Connecticut and I did not notice much because I drove slowly. Engine is starting and running fine, mileage is good. Car is capable of highway speeds over 60 mph but acceleration in situations that call for turbo boost is weak. There is no plugged catalytic converter, there are two of them on the car and I had each one of them in my hands past couple of months. You could see light through both converters and the vacuum cleaner blow-through test - my idea - also indicated that both converters were passing air fine before installation recently. The converters are plumbed into the downpipe with a short Y-type section. This problem also predates installation of the dual exhaust, I am realizing now.

The turbo itself likely is not boosting. Rereading Brickboard post (S DeWolfe - Thank you) from last May 17 led me to pay special attention to the turbo today. Test drove the car twice today 25 mi. on I-95 in Connecticut. Tried to get into boost two ways, with gas pedal by itself and with the gas pedal plus using the delete button on the transmission selector. No boost was available.

Turbo is spinning, I think. Boost needle moves from 9:00 o'clock to 11:00 o'clock or so on the gauge. But there is no or little boost and the needle does not enter the yellow boost zone.

But the drivability is not as bad as it was once about five years ago. Back then, there was a turbo problem and the car was barely capable of 40 mph and really struggled to get uphills. The culprit back then was a disconnected rod or stuck gate (?) on the other underside of the turbo if I remember right. Car was being commercially maintained back then by an expensive shop and if they had been able to wrest more repair work out of that situation, they likely would have done that. But it was an easy and inexpensive fix that time.

This time, the car is drivable, if pokey, on the highway and there is also good torque from the engine, just no zip. The engine is acting like a diesel. I wish to tow a small keel boat to Wisconsin from New Jersey with this car next few days. That looks unlikely at the moment. I have started reading the FAQ and searching posts on this. Last time I looked at the impeller was probably about last fall or so. Was fine then. I am going to go have a look of that and other parts yet this evening. If anyone could please add anything to what is available in the FAQ and in the posts on this I would be grateful. Thank you all.