Stumped on high LT's
Thread Starter
TECH Fanatic
Joined: Nov 2002
Posts: 1,889
Likes: 1
From: Lincolnton, NC
Stumped on high LT's I have been looking at my buddies car which basically has a big cam in it and headers. His Predator showed the LT's at 25 at idle. I plugged the HPT in and sure enough they were. I tweaked the VE tables some and it helped but we are still at 14 at idle, -1.6 at cruise and 0 at WOT. Nothing I can do will get the idle down. Any suggestions would be appreciated.
Idle Air Control Position is what it is. If it is in fact 0 at idle, I would suspect a leak of some sort. If you check it with autotap, I "believe" there are 2 PIDs for it. One works and one doesn't (I use efilve).
I'm going to guess it smells really rich at idle when warmed up?
The bigger the cam the more your idle Ltrims will go positive.
It has to do with the duration and lsa, your O2s are picking up some of the intake charge.
The bigger the cam the more your idle Ltrims will go positive.
It has to do with the duration and lsa, your O2s are picking up some of the intake charge.
Right, oxygen sensors don't actually measure fue/air ratio, they measure the concentration of oxygen in the exhaust. If you have both unburned fuel and air, the oxygen sensor will see the air and ignore the fuel, and it will think you're running lean. Then your ltrims will go up.
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Thread Starter
TECH Fanatic
Joined: Nov 2002
Posts: 1,889
Likes: 1
From: Lincolnton, NC
Yes, there was a rich smell of fuel in the exhaust when it was warmed up or started warm. That disipated with the lowering of the VE table. So based on the size of this cam it sounds quiet possible to have positive LT's at idle which is okay so long as they go negative at cruise and 0 at WOT. Would that be a fair assessment?
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Fast Intake
Originally Posted by snake_charmer
I am in the same boat with LTFT's at 25 at idle after new cam/fast intake install.