2000 Buick Lesabre misfire on #1 and #5

1NASCARFAN43

MEMBER
2000 BUICK LESABRE

Engine Performance problem
2000 Buick Lesabre 6 cyl Front Wheel Drive Automatic

car runs very rich with check engine light flashing, scanner shows #1 and #5 misfire at the same time and number of misfires. P0300 code stored. If check engine light on but not flashing, car runs great, but wont run well every start. When running bad, the car is hard to start, like its flooded. If it starts quick it will run fine. Wires and plugs are less than 8000 miles old. Has spark at 1 and 5, and if you unplug 1 or 5 injector, it runs worse. Upper and lower intake gaskets were replased 1 month ago with no problem after. Possible pcm, or crank sensor? Is there test for ignition module? I dont think there is engine damage ( bent pushrod, valve, etc.) Because the car will run well sometimes.

1 Reply

SERVICE WRITER

MECHANIC
9,123 POSTS

Being intermittant and check engine light also flashing intermittantly lead me to think lack of spark intermittantly or too much fuel.

I know you have spark, but are you checking when the misfire is happening? Swapping the ignition parts to different cylinders to see if the miss moves is one test.

Since you have a hard start also, I lean more towards a fuel pressure regulator. The regulator is a common problem on the 3.8, Check (leave the vac hose off for a full minute to check for fuel) it may be leaking into the vacuum hose and causing the cold start problem on this car.

PCM, crank sensor and ignition modules can still be suspects of course. The ignition coils can be swapped as described in the beginning move it to one of the other two locations and see if the misfire moves accordingly, move one of them to the 6/3 coil since this is known good.

Usually I would expect a code regarding a loss of crank sensor power if it was a problem.