: 96 Aurora 4.0

10-06-09, 12:13 PM
I know its not a caddy, but I'm hoping someone can help...

Ok so the problem started with the car hesitating bad; NO power whatsoever, couldn't even accelerate. It would buck and pop and run terribly. The code was Ērandom cylinder misfire." I replaced all the wires, coils and plugs to no avail. It would typically idle OK when this was going on. Some days it would run just fine without any issues, good power/gas mileage etc. Every once in a while it would back fire through the intake, which would lead me to believe a crank sensor. This car has two cranks and one cam sensor and from what I've found out the computer can take signals from 2 of the 3 and run correctly. So I wasn't thinking sensors because for 2 to fail seemed unlikely then return to normal. The problem seemed to be related to rain/moisture, but not 100% of the time. The last time it happened the car just stalled and now will not restart. Code now is MAF. But a bad MAF wouldnít keep the car from running. So Iím not real sure why this code is being pulled. The random cylinder misfire code is gone. It has 45psi of fuel, which holds pressure when the key is turned off. Has spark. New fuel pump ( 1-2,000 miles or so) same with the fuel filter. I've gotten it to start on starting fluid. I metered the injector harness at the injector and all have 12v. When I meter both terminals. Now I was under the impression that the injectors get key on power, 12v, and then the computer sends a ground signal when fuel is needed. I disconnected the cam sensor just to see if the ground goes away and it didn't. I also metered out the cam sensor and it has 1.5Kohms. Not sure of the spec but thatís what mine is reading. So I'm leaning toward the ECU. I also disconnected the injector harness from the main harness and un-taped it to check the wiring and all looks good, and metered fine. The only other thing Iím guessing it could be is bad wiring from the main harness to the computer. But since the upper injector wiring is ok I donít think thatís the problem. Any help at all would be greatly appreciated.

10-12-09, 12:04 PM
Check the injectors. Remove them one at a time, energize them and flow compressed air through at 50 psi. A trick to cleaning them, is have about a foot of fuel hose attatched to the injector, fill it half way up with carb cleaner, and blast compressed air through. It should spray a fine mist of carb cleaner. Each one. And from what you said, you have no bleed off.

Remember FAST - Fuel, air, spark, and timing. Throw a "C" in for compression. Do a compression test on all cylinders. Each should read above 150 psi. Always check for vacuum leaks. Intake bolts tend to loosen up on Northstars over time, as the gaskets shrink.

If you have a bit of money to spend, get a new ICM. (Ignition control module) They have been known to fail sometimes.