Hello all. I bought an 89 740T wagon last week to drive this winter and slowly upgrade into a honda and vw eater. anyways, driving around town is great as long as i don't go much past half throttle, or get going much faster than 45 mph. Driving on the highway is a whole different story. the car will go about as fast as you want it too, but getting going fast with out losing power is an extreme challenge.
At surface road speeds it will accelerate under full throttle load and the boost gauge will read about 2:00, but as soon as it is at around 4000rpm (again, under full throttle), and it is looking to change gears, it suddenly looses all boost pressure and although the throttle position hasn't changed, the tach begins to fall.
On the highway, if you go past a certain point into the throttle pedal, (slightly more than half-way, at speeds between 55-80mph), it feels as though you have let go of the pedal completely even though you continue to press. when this happens i have been simply backing off slightly at which point it "catches" again and i can continue to chug along a very conservitive speeds. basically, no matter how bad i want to, i can't pass anyone on the highway, as it takes about 120 seconds, (no joke) to accelerate from 60 to 70.
What is going on here..i can't figure it out. I was thinking overboost, but it seems to be boosting normally..fuel delivery? vaccumm leak somewhere? someone please help!..