How do u adjust the fuel/air mix on a L31 350 5.7l vortec.

[1998_K1500_Sub]

The engine is running to rich, so i just want to adjust it down a little.

Is the vehicle equipped with a catalytic converter?

What leads you to believe the engine is running rich?

 

[OhmanSWE]

Well, do you have a Check Engine Light, i.e. stored Diagnostic Trouble Codes (DTCs)?

Yes its ”exsist” but no codes no engine light everything else is no problem.

 

[OhmanSWE]

Is the vehicle equipped with a catalytic converter?

What leads you to believe the engine is running rich?

Yes i have both 02 sensors and catalytic converter.
Some black smoke and full of fuel on sparkplugs.

 

[OhmanSWE]

The only thing thats is not orginal is that its no mufflers and ofc the airfilter.
But I dont have any leaks on the exhuast.

 

[1998_K1500_Sub]

Yes i have both 02 sensors and catalytic converter.
Some black smoke and full of fuel on sparkplugs

You need to access the ECU so that you can acquire some data. If you need to know how to do this, please ask.

I think you need to access at least these parameters, to see their current values:

- long term fuel trim values
- short term fuel trim values

Also, I think you need to monitor and preferably graph, while the engine is hot and running:

- O2 sensors, in particular the two "upstream" sensors which reside in the exhaust system just ahead of the catalytic converters

I would also query the ECU for:

- stored codes
- active codes

Others may suggest additional ECU parameters for you to check.

Collect this information and report back to this thread.

You're in the right place. People here can help.

 

[1998_K1500_Sub]

@1990Z71Swede, are you around?

You might be able to lend some assistance to @OhmanSWE's L31 running-rich issue.

 

[1990Z71Swede]

@1990Z71Swede, are you around?

You might be able to lend some assistance to @OhmanSWE's L31 running-rich issue.

I'm here. I'm going by the Occam's razor theory when I suggest Spider injector or regulator is leaking. Also, ye olde Coolant temp sensor could be causing this if "stuck" on cold. (Obviously in that case it would run ok when Cold) MAF dirty Maybe? Less likely to cause a RICH condition but disconnecting the MAF should make a noticeable difference on how it runs, and to some extent verify it's function...and so on and so forth...However L31's is not something I have had the pleasure to work on... yet. Bought a 97 ECSB with a broken L31 today... I need help...