350 tbi code 44 but plugs look really rich log attached

[Fabbe]

Hi, i am having trouble with my Chevy k2500 350 tbi truck, it started running really bad so the first thing i did was changing the O2 sensor then i checked the TPS and the MAP and everyting seems ok the coomputer code says lean and the injector duty cycle is showing 5-6--700% the plugs are full of gas..
Next i am going to change the manifold gaskets, that is the only thing i could think of, checked with carburator spray but couldnot find any leeks but i ran ot of ideas.
Anyone hav an idea of what iit could be? Attached a log file if someone could help me.
Thanks//Fabbe

[Fabbe]

Anyone that can explain how the injector duty cycle works? Is it from manifold pressure?

[jim_in_dorris]

Duty cycle cannot exceed 100%. That is static, wide open. If you are looking at a log to arrive at that conclusion, you don't have the patch enabled to display the Duty cycle. That being said, I would look at what the o2 sensor is doing and the rich lean counter and BLMs and INT's. If it just started doing it, I would look at things like is the ECM seeing the O2 sensor? is it going closed loop? If I knew what mask and ECM you have, I could look at the log and perhaps give you someplace to look.

[Fabbe]

Ok, thanks. I am using a 1227747 computer and mask $42.
¨
So would i have to burn a new chip to get duty cycle to work correctly or du you meen a patch for tunerpro?
Sorry for the noob questions but i am a noob! :)

[Fabbe]

i did another test drive and the o2 was really lean, attaching the log file. After i looked at the log file i decided to chane the manifold gaskets but there was no signs of leaks.

I also checked fuel pressure and it was about 11psi.

[Fabbe]

Does the ESC regulate in open loop?

[EDZIP]

Don't be afraid to check for a bad EGR valve...

[jim_in_dorris]

The rpm is bouncing around like a yoyo with no throttle movement. your IAC counts are bouncing around as well. disconnect your IAC and see what happens. yes it is going very lean, but something is driving it there, and it looks like the IAC at idle is should be below 20 and stay there. Also, check your grounds, especially the ground from the back of the passenger side head to the firewall.

[Fabbe]

Don't be afraid to check for a bad EGR valve...

Thanks, I checked the EGR an it seems fine.


The rpm is bouncing around like a yoyo with no throttle movement. your IAC counts are bouncing around as well. disconnect your IAC and see what happens. yes it is going very lean, but something is driving it there, and it looks like the IAC at idle is should be below 20 and stay there. Also, check your grounds, especially the ground from the back of the passenger side head to the firewall.

I have checked the IAC aswell, cleaned it and did the reset procedure, when i did that it ran better for a few minutes.. Is it the lower number for IAC count the more air it is letting thrugh?

I still havet gotten the intake gaskets, i am in Sweden and it takes a while to get parts.

I noticed that the ESC is for a 305cid engine i read thet that does not match, so now i am thinking that it could have kept retarding the timing until it was way off and therefore i get the lean o2 sensor because it does not ignite?? Could that be the trouble? I am just guessing here, it feels like i have tryed every singel thing here and nothing works so i am geting a bit desperate.. :)

Anyway i have orderd new esc and knock sensor aswell.

[jim_in_dorris]

The IAC is a giant vacuum leak, the higher the IAC count the more air, it will cause a lean condition

[lionelhutz]

IAC opening or a vacuum leak shouldn't cause a speed density or MAP based fueling system to go lean. The ECM should supply the correct fuel for the extra air just like it does when the throttle is opened.

[jim_in_dorris]

Lionel, the log file has the IAC and RPM bouncing around like crazy with no throttle movement. When it reaches above about 2500 rpm, it gets crazy lean in the log. If the throttle was moving, I would suspect a fuel delivery problem, but since the throttle isn't moving, I think a bad ecm might be a consideration. also I would be concerned about grounds like I mentioned.

[lionelhutz]

As you posted, unplug the IAC then and see if the engine stabilizes. I expect the IAC is reacting to the engine rpm fluctuating.

The IAC still just adds air and MAP based fueling compensates for added air, so the IAC opening is not likely the cause of the lean condition either.

[Fabbe]

Lionel, the log file has the IAC and RPM bouncing around like crazy with no throttle movement. When it reaches above about 2500 rpm, it gets crazy lean in the log. If the throttle was moving, I would suspect a fuel delivery problem, but since the throttle isn't moving, I think a bad ecm might be a consideration. also I would be concerned about grounds like I mentioned.


As you posted, unplug the IAC then and see if the engine stabilizes. I expect the IAC is reacting to the engine rpm fluctuating.

The IAC still just adds air and MAP based fueling compensates for added air, so the IAC opening is not likely the cause of the lean condition either.

I have tried resetting the IAC and started the engine running with the IAC unplugged and it ran better but was still stumbeling and no power when reved, i cleaned all of the grounds i could find including the one behind right cylinder head and the two on the thermostat, also added one behind cylinderhead just to make sure.

When you look at the logs do you use the charts or just look at the sensor data? I find it hard to get a good overview of whats going on.
Wich definition file is best? I am currently using V3T but there i a newer right?
Wich

I really appreciate your replys, trying to lear all that i can here!