50% fuel trim..... Please help!
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Joined: Sep 2019
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50% fuel trim..... Please help! I am using decaped truck injectors in my build. Stock Lq4 pcm red/blue. The injectors have been cleaned and flow matched. I have 2 sets of these and it does this on both sets. 1 set is 75-78 lbs. The other is 73-75lbs. When the tuner put this information into the ecu it showed 52.3% fuel trim. When he put in 56lbs it would show 0 trim but would not rev up above 1700 rpm. I had other issues too that day so it didn't get tuned.
Now I got all other issues figured out and I got him to change the settings back to 75lbs and I put in New o2 sensors. Now it still shows 52.3% trim and I can rev it up to about 3200rpm very gradually, at which point it goes into open loop and doesn't come back to closed loop until you restart engine. Once goes into open loop it won't rev up above 1500. And if you try to rev it up too fast it will go intoopen loop as early as 1500-2000 rpm.
It's currently running off the map sensor. I put an Ls7 maf sensor on and he couldn't get it to run on it. This is NA build
I have checked all the wiring. All the coils are working. Changed plugs. Got good fuel pressure and regulator. I have good compression 215psi on every cylinder. Timing is correct. Temp sensor is good. Tps is good. It idles pretty good in closed loop.
The tuner thinks there's still some kind of a problem I have to fix before he can tune it. Please help!!!
Thanks!
LS2,
L92 heads,
Lq4 crank.
TSP Ls3 stage 3 cam
Ls2 1 signal cam sprocket. Double roller chain
T56 magnum
Now I got all other issues figured out and I got him to change the settings back to 75lbs and I put in New o2 sensors. Now it still shows 52.3% trim and I can rev it up to about 3200rpm very gradually, at which point it goes into open loop and doesn't come back to closed loop until you restart engine. Once goes into open loop it won't rev up above 1500. And if you try to rev it up too fast it will go intoopen loop as early as 1500-2000 rpm.
It's currently running off the map sensor. I put an Ls7 maf sensor on and he couldn't get it to run on it. This is NA build
I have checked all the wiring. All the coils are working. Changed plugs. Got good fuel pressure and regulator. I have good compression 215psi on every cylinder. Timing is correct. Temp sensor is good. Tps is good. It idles pretty good in closed loop.
The tuner thinks there's still some kind of a problem I have to fix before he can tune it. Please help!!!
Thanks!
LS2,
L92 heads,
Lq4 crank.
TSP Ls3 stage 3 cam
Ls2 1 signal cam sprocket. Double roller chain
T56 magnum
If you put it in OL what does the wideband say? Are the plugs showing lean? Why are you trying to run such a big injectors? I would personally get a set of quality injectors that better fit your application if it were mine.
Thread Starter
Registered User
Joined: Sep 2019
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In OL I got 0.00 volts on o2s. In closed loop it's jumping between 0.1 and 0.8 I don't have a wideband. I was gonna do a turbo build and that was a good cheep way to get big injectors. Others had pretty good luck.
Thread Starter
Registered User
Joined: Sep 2019
Posts: 3
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Bank 2 trim stays steady at 52.3 and bank 1 keeps jumping around in the 40s. Before I changed the crank sensor today both banks were at steady 52.3 trim.
The plugs do show a bit of a lean
You need to check with a wideband in OL. You'll find most shops, at least the shops we personally know will not tune a setup with injectors like that.
Launching!
Joined: Jan 2002
Posts: 299
Likes: 41
From: Detroit, Murder City
You have both unknown fuel delivery (injectors) and unknown airflow (new heads/cam, etc...) and you are trying to correct more than two tables at once using a single measurement (AFR error).
Good luck.
If you want to do it right, start over with known fuel delivery (injectors that have accurate data that matches their actual fuel delivery vs PW) and work on correcting the airflow model (SD or MAF, one at a time) in steady state. This is what we show in our training videos all the time to help people keep from banging their heads on the wall.
Good luck.
If you want to do it right, start over with known fuel delivery (injectors that have accurate data that matches their actual fuel delivery vs PW) and work on correcting the airflow model (SD or MAF, one at a time) in steady state. This is what we show in our training videos all the time to help people keep from banging their heads on the wall.
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