98' GS400, No cats, aftermarket intake - running very rich. Is this normal?

Spinnetti

Member
I swapped a 98' GS400 driveline into my old LS race car. I've got no cats, "straight pipe" exhaust and cone intake without the stock resonator. It seems to run fine, but its clearly rich and when I pull the plugs all 8 are sopping wet but look normal otherwise. Is this normal? I've got a race this weekend, so no time for major diagnosis, and not seeing any codes on ODB2 scan. When I did the swap I replaced one of the o2 sensors with a new one, but not the other side.

I'm tempted to do a little air bleed after the MAF to lean it up a bit as a temp "fix".
 

gloverman

Well-Known Member
Diagnoses is more than just codes. In this case I would be monitoring the trims of the oxygen sensors. They dont normally run rich , the late vvti should run lovely, conversion or not.
 

Spinnetti

Member
Diagnoses is more than just codes. In this case I would be monitoring the trims of the oxygen sensors. They dont normally run rich , the late vvti should run lovely, conversion or not.
What tools do I need and what trims am I looking for? (I have the ODB port, but no dash) It runs fine, just too rich. I temporarily opened up a small air bleed after the MAF and it was better, but still too rich. What's the failure mode of the MAF? would it just run a fixed rich map?
 

gloverman

Well-Known Member
I use my scan tool but a basic obd2 bluetooth adaptor into a smartphone can do many of the same things these days. Oxygen sensors trims is a good starting point of engine health and state of tune if you understand them.
 

Spinnetti

Member
thanks. I presume the trims are monitored live. What's good numbers? I'll also swap out the MAF and rule that out as an issue.
 
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