Fuel trim issue

[Chris]

Hi there,

I wanted to try and confirm a diagnosis with my fuel trims. I have negative fuel trim (-14 on the long term, rich condition) I noticed when I let go of the throttle and coast, stft goes to 0. Does this mean a leaking injector? I think I’m entirely wrong so I wanted a second opinion. Thank you

Chris

Topic

[Billy]

Need clarification. What are your trims at idle, 2K,and 4K? What are your misfire counts?

[Richard Kirshy]

If you suspect a leaking injector.
Isolate the injectors from the fuel system ( clamp off the supply and return lines )
Then pressure test the fuel rail.

[Chris]

[quote=”relative4″ post=194163]Need clarification. What are your trims at idle, 2K,and 4K? What are your misfire counts?[/quote]
Fuel trim at idle for stft sits right at -4 average. On load of 2500 it sits at -14 average. I haven’t done 4000

[Chris]

[quote=”nightflyr” post=194164]If you suspect a leaking injector.
Isolate the injectors from the fuel system ( clamp off the supply and return lines )
Then pressure test the fuel rail.[/quote]
I’ll YouTube that one. The lines are steel for mine

[Richard Kirshy]

I’m fairly certain you’ll find rubber fuel line attachments inline.
Most vehicles require some type of flex in rigid lines.

[Billy]

[quote=”ElCrazy93″ post=194167][quote=”relative4″ post=194163]Need clarification. What are your trims at idle, 2K,and 4K? What are your misfire counts?[/quote]
Fuel trim at idle for stft sits right at -4 average. On load of 2500 it sits at -14 average. I haven’t done 4000[/quote]

I would expect a leaky injector to show worse trims at idle than at 2500. You would also find the fuel system depressurizes when you turn off the car.
So, I would check the following, in this order:
Dirty air filter
Bad MAF sensor
Bad upper O2 sensor
FPR running excessive pressure at low vacuum

[Chris]

[quote=”relative4″ post=194174][quote=”ElCrazy93″ post=194167][quote=”relative4″ post=194163]Need clarification. What are your trims at idle, 2K,and 4K? What are your misfire counts?[/quote]
Fuel trim at idle for stft sits right at -4 average. On load of 2500 it sits at -14 average. I haven’t done 4000[/quote]

I would expect a leaky injector to show worse trims at idle than at 2500. You would also find the fuel system depressurizes when you turn off the car.
So, I would check the following, in this order:
Dirty air filter
Bad MAF sensor
Bad upper O2 sensor
FPR running excessive pressure at low vacuum[/quote]
Excellent brother thank you for that info. The only thing I didn’t rule out was the upper 02 sensor. It would make a lot of sense. I bought it new not long ago so I thought it would be ok but seeing as I bought it aftermarket and cheap, it might not be reading properly. That’s irritating. I spent 150 on the aftermarket but the oem is 350. I guess I need to bite the bullet…

[Author]

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