My car runs great but gets horrible gas mileage.I bought this car for $400.00 with a blown engine.The car had only 50,000 miles on it.The old engine had a very unfriendly 10 mm bolt in the number five cylinder(hence the cracked block ,bent valve, and a peculliar sight hole to the push rod). I replaced it a 4.7 liter with 51,000 miles on it from 928 international.I replaced all sensors with new ones and checked the ohms to make sure they are functioning properly after I got the engine running.I have no idiot lights on any more after hours of chasing ghosts.I replaced all the vacum hoses.( how much vacum should I have in PSI)Of course I put in new spark plugs.The old engine already had a set of headers, and everyone who has looked at the catylitic converter says its aftermarket and do not change it.I did replace the mid muffler and muffler with a single magnaflow muffler that I could see through.I have it timed at 8 degreesat idle and about 26 degrees at 5000 rpm.(I am not sure if this is correct ,but as far as I can tell from the literature it is)I also am not running the smog pump or the pulley fan.I have an extra electric fan on the inside of the radiator.This car never overheats. not even in the middle of summer in a traffic jam with the air conditioning on,(Yes it still works great).I do keep the belt in the car just in case.As far as the mixture screw goes I have turned it in all the way to get it to smooth out the idle.I constantly check the smell of the exhaust, the suet build up, and the color of the spark plugs.It apears to not be rich at all.(I do not have the right equipment to check it properly) but it gets between 8-10 miles to the gallon.I have put 12,000 miles on it since the swap and I am very pleased with the results.This car seems to run great, but the only other 928 I have driven is Jim Baileys and my car is very comparible in the feel of power.We will find out for sure on the 27th as I am going to go racing with him and his friends at willowsprings. Any suggestions would be greatly appreciated, also Does anyone know a good mechanic in the orange county area who can do a final tune up on it.You know someone you would trust with your daughter.This is a last resort because I have never taken a car to a mechanic before, and it is hard to trust someone else in these matters.
Thankyou