Recently, my 89 740 Turbo (auto) has been hesitating when I accelerate and losing engine power, especially when going up hills. The tach gets to 2000-2100 then lags back a bit then forward, and most of the time I have to let off the gas to get it to shift down, then get back on it to try again, sometimes it does it, sometimes not, but it is about half the time now, so it is almost undriveable.

The turbo needle is pegged when this happens, I assume trying to help the engine turn faster, but it feels like it is losing power. Since the engine doesn't rev, I assume it's not the transmission. What could this be? Something to do with the throttle? Fuel injection?

I have no ideas.

Any help would be greatly appreciated.

Best,

Nathan

Check the turbo hoses they might be collapsing or have a hole in it.

Also check the fuel filter.If you haven't changed it in the last 30,000 miles then change it.

The turbo hoses seem fine.

Is replacing the fuel filter a tough job? I am relatively inexperienced. I have changed oil and flushed transmission fluid and done tune-up tasks, but nothing like this. I have read a few instructions online on how to do this, but I am unfamiliar with some of the terminology and would have a hard time identifying the parts without pictures.

Should I pay to have this done, and if so, what would it cost?

Thanks for your help Tech, you are a kind resource.

Nathan

As long as you have wrenches you can replace the filter.
It is on the drivers side under the car.About by the seats.Unscrew both sides adn then the screw holding the filter in and it should slide out.

Hello: I also have a 740 I would suggest changeing the fuel filter to start,then you may want to check the spark plugs, I have found Bosh Platinums to be the best. Also check all the hose clamps that run from the Turbo to the throtle body. Also check the clamps and hoses around the mass airflow sensor. Espically check the large hose comming off of the turbo about 6 inches from the turbo,it gets very close to the exh manifold and I have had one burn a hole at that point. I hope this helps. :-)

Tech, I do have wrenches. I read on one website that I should pull the fuse for the fuel pump and let the car stall so that it would clear out the fuel from the line. Is this advisable? Do I need to worry about this, or just turn off the car? Also, some have said to unplug the battery. Is this also necessary?

Thanks, I'll recheck the hoses as well. I have recently replaced the plugs with NGK Iridium as well as the wires and air filter.

Today, I noticed a lot of black smoke from the exhaust. Is this a further indication of a Fuel Filter in need of replacement, or does this suggest something more serious?

Thanks again for your help,

Nathan

Back smoke means it is running rich for somereason.

You can pull the fuse if you want to I never do it.

There might be a sensor out of range and going bad.

could be the temp sensor on the fuel injection.

Well, the old filter wouldn't come off, and a friend who helped had cut the lines and take the assembly to a shop to use an impact wrench to get the nuts off. Now I can't get the line from the filter to the engine to stop leaking. I can't cut back anymore of the line or it won't reach. Do I need to just replace the whole line now? And does anyone know how long it is? And is there any kind of resource online that can help me identify parts?

Also, I found a hose dangling inside the engine. I'm not sure where the one end is supposed to go, but the unattached end is cracked, and the attached end is on some small gizmo mounted to the drivers side shock/strut housing. What is this, and what should it be attached to.

I know, I should just be taking this somewhere to get it done as I am obviously way to too green to attempt this stuff. It would be worth almost anything to get the 7 hours back and now I am carless as this is my daily driver. What was I thinking?

Thanks again for your help,

Nathan

What exactly did you do to try to repair the line?

Well, there isn't much I can do to repair it. It is a hard plastic inside and a foam-like isulation outside. I put the end in very hot water for up 10 mintues and then tried to push the ribbed insert in. It just wouldn't go far enough, and the plastic had already formed its shape.

I am going to pick up the needed fuel line hose today, and it is ridiculously expensive, over $6 a foot. So I'll be set back over $60 just for hose, which puts this seemingly basic project over $100 so far. At least the fuel line will be new.

I still need to know what this little hose is that was hanging down from a gizmo mounted on the drivers side shock housing back and above the battery. It is powered and has two vacuum hose connections on the bottom. The attached end of the hose was on the rear-most connection. Does the other end loop back to the other connection, or is it supposed to go to something else. Also, does anyone know the name of this thing?

Thanks,

Nathan

Im not sure what valve you are talking about.
I will have to try to look on a car on monday.

I believe what your talking about is the control pressure regulator.

What should the other end of the hose be attached to then?

Thanks,

Nathan

Well, the car was running fine for a week after replacing the fuel filter. Now it is back to the way it was, not getting enough gas it seems and blowing a bit of black smoke. (although I am not sure that is unusual, isn't the exhaust from the turbo when it is spinning hard black?) Today when I started it, the engine was shaking like it was misfiring, but it seems more like the fuel isn't getting to one or more of the pistons. What should I do next?

Thanks again,

Nathan

Anyone have any ideas on this? Do I need to clean something or replace something between the fuel line and the injectors?

Thanks again,

Nathan