My 94 Buick LeSabre misfires almost constantly on cylinder 6, but it also
misfires a lot on 5 and some on 3. I get only error 300.
I have the Actron ScanTool that tells me what the car is doing and during
the same space in time 1,2,3 and 4 is firing while 6 is not. Sometimes 5 and
6 are not firing or, less often, 3 doesn't fire.
Also, if I connect a timing light to each spark plug wire while the engine
is running I see how often the strobe light doesn't flash. 6 is the worst,
then 5, number 2 I thing does it less or almost never.
The misfiring happens randomly.
The Crankshaft sensor was replaced 30,000 or 40000 miles ago. Do you think
it could be the Ignition Module?
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?
If you have confirmed that these are definitely the cylinders missing, then
try a power balance test or a compression/leak down test to make sure this
is not a mechanical problem. Some scanners will do a power balance test by
killing the cylinders and comparing rpm drops. This would show whether the
suspect cylinder was making comparable sealed compression compared to the
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
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.
When it stalled there were no noises or anything else, it just stoped
Could it have anything to do with the scurity system?
If you spray carb cleaner into the intake will it start, do you have
injector pulse, check with a noid lite. So now you went from a miss to no
run, is this correct? Try disconnecting the maf, see what happens after the
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.
Now we are down to the problem,check all the ecm and inj. fuses first. then
get it on a scanner and see if it reads cranking rpms You threw us off with
you saying you saw the injectors spraying. Last if nothing wrong shows, try
tapping the ecm fairly hard with a screwdriver handle while cranking ,see if
you get a momentary pulse on the noid, also check the harnesses are plugged
into the ecm firmly.
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
5 misfire the worst.
The spraying I saw on the injectors before, was when I connect each injector
to the battery directly just to see if they worked.
Try switching coils and see if the miss moves, earlier post you said you
could see the miss fire with a timing lite, does it have a dead miss or does
it skip intermittently. Also try spraying some water around the wires and
coils when dark, see if you see any arcing.
Switching the coils makes no diference.
It skips intermitently, but cylinder 6 misses almost continuously, sometimes
5 does that.
There is no arcing with humidity.
Today I did an expriment. I disconnected one injector at a time and cheched
cylinders missfired with my ScanTool. Here are the results:
#1 disconnected ---> #2 misfired
#2 disconnected ---> #1 misfired
#3 disconnected ---> #6 misfired
#4 disconnected ---> #5 misfired
#5 disconnected ---> #4 misfired
#6 disconnected ---> #3 misfired (and #2 a couple of times)
I checked the spark plug wires and they connect each coil to the right spark
The tool, when you press the key to start recording, it reads data for
about 9 seconds, plus about 5 seconds from before, and plays it back in 13
frames taken about, more or less, 1 second apart. Then I can scroll up and
down through it.
Besides the usual error 300, ramdom misfiring, today I also got the error
406, pindle position error, EGR.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.