fuel trims

[tucamote]

I currently have an issue with my tune. At start up it bank one will be at .876
and bank two will be at 1.245. after it sits there and sputters for about a min it cleares up and both banks are almost the same. What would cause this This is on a lightning with 2.6KB built satge 2.5 cam from MHS. Any ideas I got 60 lbs injectors

 

[01yellercobra]

How old are the O2 sensors?

 

[tucamote]

few months old

 

[01yellercobra]

It sounds like the sensors are taking a little bit to warm up and the computer isn't set up for it. Are you running headers?

 

[tucamote]

Yes I got longtubes

 

[papa]

Try to delay open loop.

 

[tucamote]

would a leaking exhaust cause this it was working fine then it just started to do this.

 

[01yellercobra]

It depends on where the exhaust leak is. If it's right before the sensor then it will affect the readings.

 

[ytngt]

You could try the following:

Switch o2 sensors to the other bank, see if fuel trims follow the o2s.

Weld in bungs one each side and use a wb o2 to determine real af ratio.

 

[tucamote]

I swapped o2 around same thing. I also noticed that when i start it first thing it does that one bank way off from another then it i drive it after its warmed up its fine. Also if i stop and shut the truck off for 10 mins and turn it back on same thing then it clears up. Any other ideas?

 

[01yellercobra]

I'll bet it's the O2 transport delay in the tune. It needs to be lengthened to make up for the length of the headers.

 

[04Ryan]

And if you can increase the heater duty cycle for your 02's by 20-30%...the Mustang PCM's let you change this. Not sure about the Truck PCM's...

 

[tucamote]

well I asked my tuner and he said the delay is the same on both banks and only bank one does it.

 

[01yellercobra]

How much delay did he add? Did he say if the heater duty cycle was increased?

 

[tucamote]

Well I have more information on my trim problems. Today I drove the truck and the roads were wet well it started to act up it seems like I am getting water somewhere and causing it to mess up anyone have a wire diagram for the fron o2 sensors on a lightning?

 

[tucamote]

Well I replaced both o2 sensors added another wideband to monitor both banks. I also replaced manifold gasket that had a small leak. I still have the same problem. I also noticed that bank one will always be leaner that bank two and some times bank 1 will go super rich into the 12.5 afr and bank 2 will be at 14.5 to 15 at a stop light. I get no check engine lights either. What would cause this problem?

 

[01yellercobra]

Normally I'd say swap the O2's, but you've already replaced them. How is the truck running with the trims drift like that? Is it running normal or is running rough? Have you compared the STFT's to when the widebands drift? Make sure the computer is seeing the same thing you're seeing.

 

[tucamote]

truck runs like shit the short term fule trims change also I dont know what to look at any more

 

[01yellercobra]

Do you have another tune you can load just to see how the truck reacts?

 

[tucamote]

I have 4 tunes for it and the same crap. I also changed the injectors to some 60s still same shit. I currently have rc750 in it. I went out there today it was really lean bank one and i pulled all four injector plugs and it seemes to run the same way could it be that the pcm is not telleing them to open???????