Problem with engine 89 GXL
 

I just bought this car off someone who installed a junk yard engine after his went out. He told me he was getting 15lbs of compression, then I noticed that the compression checker he was using was in the trunk it was for piston engines... So I figured if he was getting 15lbs on one spark hole and losing the rest out the other the compression should be ok, but I havent checked yet. (just a hunch about possible problems with the engine) The car was in really good shape so I figured it was worth the purchase. No I havent gotten around to messing with it yet and im just going off what he told me was wrong with the engine... He said it would turn over but it would only backfire. Any ideas? Ask me questions for further information... I will tell you as much as I can find out. I get the car saturday so I am just trying to get a head start on fixing it.

Remember the thing about the compression was purely just a hunch. I know it isnt scientific... it does make some sence though. Thanks for not flaming.

do the usual dumb test and crank the car with the spark plugs & EFI fuse pulled. If you feel 3 strong wooshes of air per revolution per rotor you should be good to go with compression.

Ok, What about the backfireing when cranking it over? If it has good compression what could possibly solve that problem?

TPS, needs tuneup, etc..