1980 Porsche 928 doesn't accelerate properly! Please help me.?

tyefu04

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Nov 10, 2011
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Hello. So I have a 1980 porsche 928. Has a dead battery but if i jump start it, it starts right up. It revs fine if its in park or neutral but if i put it in drive and try to give it some good acceleration it kinda stalls. So my uncle passed away and I now have his project 928. The engine shouId've been complete. I know he drove the car occasionally and he never mentioned a problem to me. I know he had a porsche mechanic go through the engine and replace gaskets, belts, tune up etc... So I don't know a lot about the car and don't have the money to take it to someone. I really just want to figure it out so I can trade or sell it. The engine doesn't shut off but I have to wait a few seconds before it re-engages. If I barely press the throttle it will accelerate through all gears and reach a decent speed. For instance if I am at a stop sign and try to merge into traffic and give it a decent amount of throttle to avoid being hit, I have no chance. Its almost like how a car behaves if its red-lined. I try to give it power and there is nothing there. Any ideas? Thanks in advance.
I'm not sure how to respond to your questions. Think I'm going to trade it. Just got offered an Audi A6. Had several other good offers, such as two newer street bikes, 4x4's etc... However I need to figure out the problem before I trade. It also has less than 50,xxx original miles.
 
could be a lot of things..alternator, pcv, coil ...among other things. You'd spend a lot of money just guessing.

those are cool cars, what do you want for it?
 
A 1980 has bound to have a lot of water condensed in the gas tank.
Change the filter.
Add a can of dryer, (alcohol).
Then check the fuel pressure.
I beleive this is the low pressure AFC system, so should be about 28 psi.
( check with the gauge in a T, not blocking the flow, or else the pressure will have no relief and the pump will be damaged.)
If the fuel is ok, the most likely it is the vacuum advance.
Diaphrams crack and leak.
If not that, then you could have a coil break down.
Use a timing light to see if the spark weakens or gets erratic.

There is also the air pressure sensor and throttle position sensor, but I can't remember how you check them any more. The temp sensor should be between 2000 and 200 ohms, cold to hot.
Catalytic converter can also be clogged.
If so, you will get excessive back pressure at the exhaust test pipe.
 
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