928wolf

My '85 928S Euro 5 speed is not running properly. Acceleration is very jerky and doesn't feel like it has the power or torque it should. Between 3000 and 5000 rpm under full throttle load it is jerking and hesitating. Especially in 1st gear it feels like it falls into a hole in that range. I did some informal 0-60 runs and I couldn't do any better than the 8-9 second range. I'm not a professional driver but I think I should be able to get a lot closer to the 6.6 second time that is claimed in the OM.

From reading the Service Manuals it looks like there are a number of sensors that either advance or retard the timing, I plan on doing a thorough ignition system check: timing, resistance in the various components, sensor continuity checks, etc. It appears that any one of these not working properly could retard the timing.

I also have an intake refresh planned in my future. Do I need to go ahead and do that? Maybe it just isn't getting the consistent full fuel flow at max throttle?

The car only has 33,000 miles on it but it almost 30 years old and sat for many years without being driven very much. It just seems like this car should accelerate better than my wife's Mitsubishi Eclipse (V6, 6-speed), which it sadly does not.

Help!

andy-gts

from what I have read here, intake refresh sounds like a must to get rid of false air , seal up all leaks and vacuum leaks.

sounds like a nice find !!! car in the avatar looks nice!

GregBBRD

Start with fuel especially since it has such low mileage. The really low mileage means that it had to sit around and most likely had some really nasty fuel in it, at some point in time.

Start at the tank. Remove the in tank pump and make sure it works and the short rubber coupler is attached. Replace the fuel filter. Check the fuel hoses for deterioration...replace as needed.

Then try it.

MainePorsche

Great looking car.
Add a bottle of Techron and 8 oz. MMO (Marvel Mystery Oil) to a full tank. Put some miles on it. After 2-3 times of this change out the filter. This will loosen up some of the varnish in the tank and kick it out to the filter. The MMO also lubes the fuel pump a bit. I add this combo to every 4th-5th fill up.

928wolf

I've put 2 cans of BG44k through it in the last couple of months, to some limited effect. Haven't changed out the filter, although that was done about 2 years ago by the PO.

Thanks for the compliments, I lucked into this car and just had to have it.

James Bailey

It is the 4.7 twin distributor 2 valve motor I presume ?? running that poorly is more than just retarded ignition timing. Will it pull to over 6,000 rpm ?? Also what was done to the exhaust when it was Federalized ?? They often put on cheap way too small a cat convertor. It would be good to do a compression check , check the belt that ties the two ignition rotors together, check the firing order of the plug leads, check the camshaft timing especially if one bank has low compression , ....have YOU ever seen it running well ???

928wolf

Thanks for the suggestions,

928wolf

OK, step 1 ordered new fuel filter, will test fuel flow per the Service Manuals.

Fingers crossed.

James Bailey

If a fuel filter fixes anything it will be the first time I ever heard of that after about 20 years and millions of dollars of 928 parts sales.....same for auto trans filters....but it is cheap and pretty easy but you said the filter was only two years old !!!