Misfire in 6th cylinder engine does no turn over without jump?

BRETTHOLLYWOOD

MEMBER
1996 PONTIAC FIREBIRD
3.8L
6 CYL
2WD
AUTOMATIC
50,000 MILES

I have trouble shot via different forums on the most inexpensive fixes. I filled the car with premium fuel thinking it was a lean misfire due to bad fuel. Replaced spark plugs and wires as well as a new coil pack and made sure they were in the right firing order. Car still throws a misfire code in the 6th. After taking it in, once to get it diagnosed, 2nd to get plugs and wires installed, each iteration the car ran worse. Before the vehicle went to the shop the misfire would affect the acceleration. After taking it in to get the plugs and wires replaced acceleration was fine but now the idle is acting up. Vehicle will cut out after a short period as the rpm jumps above and below 1000 the voltage meter will jump as well. Took my battery and alternator in to get tested and both checked good. Charged the battery as it was low (31%) put the charged battery back in, volts read 13.5 and car will just click multiple times and won't turn over without a jump. When the car does turn over it kicks raw fuel out the tailpipe and the exhaust sputters rapidly. I'm assuming this may be multiple issues. Not sure what to do next.

Thursday, March 30th, 2023 AT 1:09 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,106 POSTS

Hi,

If raw fuel comes out of the exhaust and cylinder 6 is the cylinder that misfires, it sounds like you have a leaking fuel injector. This can certainly damage the catalytic converter and create new problems.

The idea that you need to jump-start it even though the battery is fully charged is odd. Keep in mind, when you jump-start the vehicle, you are not increasing the voltage. You are simply providing 12v in the event of a weak battery.

Here is what I need you to do. First, confirm the battery terminals are clean and tight. Also, confirm the ground to the engine block from the battery is in good condition. If they are both good, remove the cylinder 6 spark plug and see if the starter can turn the engine. I suggest this because it sounds like you may be getting raw fuel into cylinder 6 creating a hydrostatic lock.

On the other hand, if you can check the fuel pressure and pressure drop-off, that can tell us if there is a pressure issue or even a leaking injector.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Try this and let me know what you find.

Joe

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Thursday, March 30th, 2023 AT 7:42 PM