Cadillac Repair: fuel system, fuel pressure gauge, cadillac seville

Question
I have a 1989 cadillac seville 4.5liter v8. It has been losing power as I accelerate, sometimes bucks and dies out. Info center shows no problems.Just did a tune-up and it still has the problem but it is not consistant. I don't know what else on the fuel system could have a problem. Has new fuel pump less than year old.

Answer
Hi Anthony, From the way you describe things it would appear that the fuel filter or fuel pump might be acting up. To eliminate that as a problem you would need to install a fuel pressure gauge and make sure the pressure is 12psi. What I would do is tape the gauge to the windshield so you can see what is happening when the problem occurs.

     Another thing that could be happening is the ground cable where it attaches near the starter could be loose or corroded. If it is still attached to the engine mount or a/c bracket it needs to be located below the bracket that attaches to the starter. If the bracket isn't there then just get a M8 X 1.25 X 3/4" long and bolt it to the block after sanding both sides of the battery cable end clean as well as the engine block. If the bracket is there then place the battery cable between the engine and the bracket after cleaning the bracket of all the paint in the bolt and cable area as well as the cable end. That might take care of your problem.

     After that reading the codes to see if any are stored in the computor memory would help. Then grab a scan tool and see that the tps is around .58 volts at idle. The oxygen sensor needs to bounce around between .200-.800volts with the engine running and .45V with the key on. The MAP sensor is around 99 with the key on and 34 with the engine running. The BARO reading needs to be correct for your area.

     I realize that you just did a tune-up but if you put any plugs in othere than the AC Delco brand that could be a problem especially if they are Bosch Platinums or Autolites. Take the distributor cap off and make sure there is a coil ground terminal and that the coil isn't arcing. Or the cap and rotor aren't burned or arcing.

     The last thing to check is to tap test the engine computor while the engine is running and see if it stumbles or dies. If it does then it has a bad soldier joint and needs to get replaced. Don't use a hammer or you could damage an otherwise good ECM. Instead use your fingers or knuckles.

     Start with those things and let me know what your readings are if you need more help. Bill