View Full Version : 4.9 litre tune up 94 deville

02-02-12, 04:08 PM
Ok guys. Cad is missing a little & mileage is down to 16mpg. I saw a 99 cad for sale the other day with n*star & owner claimed 30 mpg. If i thawt that was achievable, i might consider. I got this car w 100k miles & it now has 156k. Ive repl. All the guts in the distrib, and run good gas in it. Is it time for plugs & wires again? Any other ideas besides verifying Timing and cleaning egr tubes? The car runs well, but could run better. No codes except Anti lock lite which ive chosen not to investigate yet? Thanks for your input.

02-04-12, 09:01 PM
You might pull the plugs and get an idea of which cylinder(s) could be a problem. I know they're a pain but if your thinking about it, you were going to do it anyway. You might have injector problems, you could check those out doing the stethoscope method. Not sure how different a power balance test would be on a 94 from my 93, but that's another test you could do. Before you dump more parts into it, if you don't have a FSM get one off ebay. There are some good deals on ebay sometimes.

02-06-12, 12:13 PM
Not trying tobe uninformed, but what is the stethoscope method? It is a throttle body injector system which looks like a 4 barrel

02-07-12, 07:14 PM
Oh....no just get a real long blade screwdriver and hold the handle up to your ear. When the engine is running hold the blade of the screwdriver to the body of the injector, you will hear a definite click sound from it.

02-09-12, 11:28 AM
If you decide to change the plugs and wires, I did a writeup in this section for my 93. Different body I know, but since it's same engine, it should be the same.