Misfire

[HiHoeSilver]

Cant find a vacuum leak. Pulled plugs 2 and 4 are wet with fuel but 6 and 8 look great. Did find a vacuum leak behind the cats where the flange is could that cause it?

Not really. Did you inspect injectors abs their o rings?

 

[callahan347]

Not really. Did you inspect injectors abs their o rings?

Dont believe that is the issue. Had the same problem 2 and 4 being wet thought it was an injector issue so I replaced the entire spider unit

 

[bigfootchiro]

Could be vacuum leak, not enough fuel due to weak pump or stuck injector, etc. Check all the way up to the manifold from the upstream O2 for any cracks in the piping. Also, check all vacuum lines. You can spray brake cleaner or propane around the intake, listen for change in idle, and that will tell you if there’s a vacuum leak. Make sure to cover the alternator with a rag when you do this. Your fuel trims are off for a reason, and now it’s time to figure out why.

 

[callahan347]

Could be vacuum leak, not enough fuel due to weak pump or stuck injector, etc. Check all the way up to the manifold from the upstream O2 for any cracks in the piping. Also, check all vacuum lines. You can spray brake cleaner or propane around the intake, listen for change in idle, and that will tell you if there’s a vacuum leak. Make sure to cover the alternator with a rag when you do this. Your fuel trims are off for a reason, and now it’s time to figure out why.

It seems more like its reading lean but isn't. Cylinder 2 and 4 are getting excess fuel. Pump and filter are new. Replaced the entire spider unit and new gaskets. Have sprayed starting fluid and used propane around the intake with no signs of a vacuum leak. 02 sensors were replaced last fall and appear to read ok with a scanner no signs on laziness

 

[HiHoeSilver]

It seems more like its reading lean but isn't. Cylinder 2 and 4 are getting excess fuel. Pump and filter are new. Replaced the entire spider unit and new gaskets. Have sprayed starting fluid and used propane around the intake with no signs of a vacuum leak. 02 sensors were replaced last fall and appear to read ok with a scanner no signs on laziness

It is reading lean. Your +8-9 on bank 2 is lean. It's adding fuel. The fact that it comes back down on throttle says vacuum leak because you are getting away from stoich. If it was a fuel delivery issue, your trims would go even higher on throttle.

 

[bigfootchiro]

Weak fuel delivery mimics vacuum conditions. When PCM detects too much air (vacuum leak), it responds by adding fuel to compensate and bring AFR back to stoic.

 

[HiHoeSilver]

Weak fuel delivery mimics vacuum conditions. When PCM detects too much air (vacuum leak), it responds by adding fuel to compensate and bring AFR back to stoic.

Until it's under load. Then they go opposite.

 

[callahan347]

It is reading lean. Your +8-9 on bank 2 is lean. It's adding fuel. The fact that it comes back down on throttle says vacuum leak because you are getting away from stoich. If it was a fuel delivery issue, your trims would go even higher on throttle.

Oh ok I understand. I cant find a vacuum leak anywhere. Are there any common leak areas for the bank 2 side?

 

[bigfootchiro]

Until it's under load. Then they go opposite.

I wasn’t gonna go that far with it yet lol

 

[HiHoeSilver]

I wasn’t gonna go that far with it yet lol

I did because he showed us +8-9 at idle and back to 0-3 at 2500 rpm.