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Dan, Technician
Category: Buick
Satisfied Customers: 24425
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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1997 buick lesabre: cyl..coil, and fuel injector, injector circuit

Resolved Question:

1997 buick lesabre with code p0306 (cyl six misfire)
I have checked compression, replaced plug and wire, coil, and fuel injector, injector circuit is working. Clear error and it comes back imediately
Submitted: 7 years ago.
Category: Buick
Expert:  Dan replied 7 years ago.
What was compression compared to the other cylinders? You checked to see if one side of the injector has good power and the other side pulsated ground off/on? When you reset the light how quick does it come back? Thanks
Customer: replied 7 years ago.
yes and light comes back right away,
Expert:  Dan replied 7 years ago.
What did you get for a compression test? Since it comes on right away means its a bad misso n this cylinder.....And since each coil controls 2 cylinders and only one is misfiring and coil has been replaced we know its not related to the the problem is related to the injector circuit or the compression......So what was compression? And with a testlight it flashes off/on on the ground side? Thanks.
Customer: replied 7 years ago.

my compression testor is not the best but all cylinders read within a couple of pounds of each other 118


i used a meter to see pulses not a test light, but it seemed to be working consistantly.


One other bit of info. the car backfired during startup and the code came on a minute or so after that

Expert:  Dan replied 7 years ago.
Ok, well if compression is about the same as the other ones within a couple pounds that shouldnt be the problem.......voltmeters are hard to accurately use to test the ground pulsating off/on since it happens so fast then dont register it the best......If you can check it with a testlight that would be the best option.......If testlight doesnt flash then check the same wire going into the pcm to see if it flashes if it flashes at the pcm but not injector replace wire. If it flashes at both places then you likely have a intake gasket leak or headgasket leak causing too much air or coolant going on in that cylinder but that usually doesnt cause the check engine light to come on right away......Since it comes on fast is a good indication of a injector circuit. Let me know if you have questions, thanks.
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Customer: replied 7 years ago.

if i had an intake leak wouldn't i get a lean error code

there are no other codes

Expert:  Dan replied 7 years ago.

You would usually get a lean code but not always.....If its only on that one cylinder then it wouldnt be bad enough....There was a technical service bulletin released for this vehicle that a bad intake gasket or intake could cause this problem......If your 100% sure the injector is firing then replace the intake gasket and/or manifold. Let me know if you have questions, thanks.


Customer: replied 7 years ago.

when i said it comes on fast i mean within a minute of startup. isn't replaceing an intake or head gasket alot of work with out proving it some how?


the bulliten you sent the link for refers to coolant consumtion but doesn't say anything about misfire. is there more to the bulliten than the link shows

Expert:  Dan replied 7 years ago.

Well if its going through coolant that would cause a misfire test you can do a cooling system pressure test and if it doesnt hold pressure then this is your problem. That is the full bulletin, let me know if you have more questions. Here is another TSB that you will want for when replacing. Thanks






Customer: replied 7 years ago.

Its late here so I will try pressure check tomorrow

I'm not to excited about changing a gasket unless I can prove there is a problem. it hasn't been using any coolant as far as I can tell. I will also try a test light on the injector





Expert:  Dan replied 7 years ago.
I hear ya on not wanting to replace the gasket if your not sure........but definitly use the testlight to verify wiring is good and if it is and considering you already replaced the injector and coil that is really the only other possible problem. But let me know what you find out tomorrow or if you have more questions, thanks.