Misfire on 2006 CXS

LoyalCustomer

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I have a 2006 Buick Lucerne CXS with the Northstar V8. I have been chasing a misfire for a while now. I am hesitant to make repairs ($$$)as it has 116xxx miles and needs front end work as well.

First I had a p0305 code, misfire on cylinder 5. I was debating changing the coil on #5. Insetead I changed the plugs and all were pretty worn but #5 was completely worn. I then moved the suspect coil from #5 to #6. Now I get a p0300 code for multiple cylinders.

Next I added seafoam twice to try and clean the injecters out. The misfire is still going strong to say the least.

Here is what I have noticed so far.

Misfire seems to occur when:

engine is warm/ warming up (its currently 15 degrees in WI)

When I am idel/stopped at a light. (eases up when I put in Neutral)

If I put the gas down and hit 4500-5500 RPM
(It will also shift very hard and trigger Service Stabilitrack and T/C)

When pulling from a light I hear a knocking



Misfire seems calmer when:

First start the car in the AM (average temp prob between 10-20 Degrees)

driving at around 2000-2500 rpm
(could still be misfireing it just seems calmer)

Misfires still but much lighter when in Park and even less misfire in Neutral

Full tank of gas (could be because I used seafoam the last few tanks)


I will keep reporting and answer questions, Thanks in advance
 
Ok new coil is on its way. I will post results after its installed. Thanks for the input and link
 
Did you check the harness that plugs into the injector?
The exact same thing happened with my 2006 Lucerne CXS. I spent soooooo much money on that thing trying to get it fixed and ended up fixing it myself. The harness had rust and corrosion in it causing a current blockage. I sprayed it with some electrical components cleaner and it's been back to its normal self ever since.
 
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