my 740 has been weak. it starts fine. it idles and doesnt; seem to miss but there is quite a bit of vibration. during driving it's sluggish. If I were to floor it and try to spin a tire around a corner in the wet it would not have that much power to even spin one wheel. takeoff is slow. It'll drive along ok but if I stomp the throttle a little it reacts but very slowly. If I put it to the floor it will gear down and go, but it's still hesitant. it will however get up to speed and have power.

I dont think it's had any serious issues, it feels like it's just not getting the fuel . I replaced the fuel pump fairly recently and swapped out the fuel pressure regulator, the one with the line that connects to the manifold.

I dont have a fuel pressure gauge, I was thinking of trying to connect to the metric fuel line using old parts like a fuel line and part of the fuel rail for the fittings, maybe a gauge like for reading water or air pressure would be ok just for a test.

Im wondering if I might have a big vacuum leak ? bad intake gasket maybe?

other cars seem to rely on input from the throttle sensor. I haven't looked into that , does the 740 have a throttle position sensor that might go bad and cause this?

I have lots of spare parts to use for testing from another 740 sedan I disassembled. I could try switching the fuel rail and injectors..

the sensor in the distributor that senses TDC went bad. I just swapped for another distributor. but it runs so I dont really suspect that as a fault. I'm not sure I got the timing spot on, I can rotate the distributor a bit. maybe check the timing with a timing light..

I've done the timing belt before. I'm starting to wonder if it could have jumped a tooth or something. If the balance shaft wasn't right that could account for the vibration I'm seeing at idle. it seems to shake more than normal but it doesn't seem to be misfiring.

I just replaced the other belts but didn't open the timing cover.

Ill plan to pull the plugs, maybe check with propane to see if I can find any vacuum leaks. Im a bit stumped as to what would be the most likely cause. I cleaned the mass meter with some spray cleaner for cleaning injectors last weekend and didn't see significant change.

the car has 160K on it, Ive owned it for about 10 years since it was 80 K and this issue of it being "weak" seemed to creep up slowly. Ive had it on and off the road in and out of use.

i got some injector parts so I thought maybe I should soak some other fuel injectors in sea foam and connect them to open them. and try replacing the pintle and filters and o rings.. then swap them all.

I can check if I have any plugs that look different from the others.

head gasket isn't blown, no water loss or signs of a head gasket failure. I should verify the compression. temp gauge reads pretty normal.

I think something is causing it to not get as much fuel or as much fuel pressure as it should. maybe it isn't sensitive to the manifold vacuum or the throttle position? I did not get gas out of the hose that connects the fuel pressure regulator to the manifold. I could tee in a vacuum gauge but I dont know what vacuum I should expect.

any tips or ideas are greatly appreciated. Its an /88 so it does not have the little box with a jumper thing to check codes like years later did, can I still check the fault codes?
thanks , Phil