94 Buick LeSabre misfires, error 300

I replaced the spark plugs and wires and it does the same thing.

I have new information on my 94 LeSabre. I replaced the wires and spark plugs. I also replaced the Ignition Module and Coils with ones from another LeSabre that works fine. I switched the injector 4 and 6 with the 1 and 3. Fuel pressure is normal. The same cylinders as before keep misfireing. In my other message I said the worse two where 5 and 6 but I should have said 4 and 6. In any case 4 and 6 were the worst and they still are. 6 misfires almost every single time. Any idea what may be causing this?

Antonio

I did check compression and the highest was 170 psi and the lowest was 135 psi. From 1 to 6 the compression was: 150, 170, 150, 165, 135, 170. In the manual they say the lowest shouln't be less that 100 psi and the lowest reading cylinder must be 70% of the highest.

My tool doesn't do a power balance test. What I did was to check the compression while the engine was running in idle on cylinder 6 and 1, most misfires and least, and I got 60-62psi on both. Does this mean anithing?

From bad to worst. This morning the engine was running as yesterday, misfiring but running. I started the engine to check it again with my ScanTool. A few minutes later it stalled and didn't start again. I have the original Computer that went bad maybe 2 or 3 years ago. The engine worked rough with it but worked; I tryed it before yesterday and the engine started and run.

So, gessing that maybe the Computer went bad (I had boght it used) I replaced with the original I had from before, but the car didn't start either. So I am assuming that its not the Computer but I have no idea what to look for next.

I checked, again, the fuel pressure, for spark in the spark plugs, for disconected vacum hoses. Fuel pressure is about 42 psi, there is spark, and I didn't see signs of vacum leaks.

Trying to fix this non-start condition I replaced the Crankshuft Sensor and the Camshaft Sensor. Nothing!

When it stalled there were no noises or anything else, it just stoped running.

Could it have anything to do with the scurity system?

It was running, I hadn't done anything, it just stalled and wouldn't start again. I sprayed starter fluid into the intake and the car tried to start. I went to two places and they didn't have the Noid Lite, maybe tomorrow I will find it in another store.

I just tested the injector's harness with the Noid Lights and none of them as a pulse. What could be causing that?

My guess is it slipped a tooth and the timing's too far off. My car did that, too - running fine, then horrible for a few seconds and no starting. The chains do stretch.

This is getting confusing. :-) The car is back to the old problem. The not starting condition was a fuse under the dashboard next to the globe compartment. Now that it starts, if does what it was doing before, which is, cylinder 5 and 6 misfire. But 6 more that 5, sometimes it's the other way around. Rarely, 2 also misfires a little.

Where I see the misfiring it's with my ScanTool. If I listen to the injectors with a mechnics stethoscope I hear them clicking and they never miss. When I looked at injector it sprayed. If I remove the spark plug wire and test it looking at the spark, it never fail to spark. But I feel the engine running rough. I switched injector 6 with another and no difference. I also switch spark plugs 5 and 6 with others and no difference, still 6 and

The spraying I saw on the injectors before, was when I connect each injector to the battery directly just to see if they worked.

The error given is:

P0300 Cylinder misfire detected (ramdom)

Sounds like the timing is off and the computers can't compensate. Not sensor-related, but mechanical.