abnormal Lean at idle

jesus said:
No built motor bnrs4 with supporting mods. I was able to get a log today of the car both when it wanted to run lean & when it wanted to run rich. is there something you guys see that I'm not catching? I notice that the MAF reading in lean condition runs closer to 1.93-2.0 g/s than rich running passed 2.3g/s. Would this be pointing at a failing MAF sensor ? The sensor its self is a denso MAF
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If it isn't an OEM MAF that may be the issue - these cars are very picky about non-OEM. I've had issues in the past, it may be worth a shot if you know someone who has an OEM MAF you can test.
 
jdab555 said:
If it isn't an OEM MAF that may be the issue - these cars are very picky about non-OEM. I've had issues in the past, it may be worth a shot if you know someone who has an OEM MAF you can test.
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Denso 1976040 is "supposed" to be the OEM MAF according to our proven parts list but OEM still remains the reccomendation for MAF, I don't recall anyone coming back with a "tested it no issue" post
 
If i cant get my hands on a oem sensor whats the best way to test this maf that i have in the car now ? also do the logs show anything to you guys ?
 
What intake size are you running? First log here is 2.5" intake, second log is up to 3" intake, both were taken at idle at the beginning of my tuning process. You can compare MAF voltage and g/s, looks like it may be low for what it should be in both columns.
 

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Rather than opening a new thread, I’m having a similar issue (AGAIN) as the OP. A couple of you guys helped me with this last summer so you may remember. The engine was misfiring and running, lean all the time, and it ended up being bad HPFP internals and a clogged injector. Replaced the MAF, rear o2s, injector along with getting the others cleaned, replaced the HPRV, HPFP internals, and installed the CS FP oring kit. The car has been running and driving perfectly ever since with solid fuel pressure and AFR’s although it never passed the PRV test since. I’ve disassembled the HPFP for cleaning and inspection several times since but never found anything.
Last night it started idling in the mid to high 16s but returns to normal AFR’s as soon as the engine is under a load, but seems to be a little delayed. Still drives normally with solid rail pressure even under WOT.
my suspicion is the spill valve, which I am leaning towards buying a used HPFP and switching my internals over but I hate guessing. Any thoughts?!
 
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AndrewC08MS3 said:
Rather than opening a new thread, I’m having a similar issue (AGAIN) as the OP. A couple of you guys helped me with this last summer so you may remember. The engine was misfiring and running, lean all the time, and it ended up being bad HPFP internals and a clogged injector. Replaced the MAF, rear o2s, injector along with getting the others cleaned, replaced the HPRV, HPFP internals, and installed the CS FP oring kit. The car has been running and driving perfectly ever since with solid fuel pressure and AFR’s although it never passed the PRV test since. I’ve disassembled the HPFP for cleaning and inspection several times since but never found anything.
Last night it started idling in the mid to high 16s but returns to normal AFR’s as soon as the engine is under a load, but seems to be a little delayed. Still drives normally with solid rail pressure even under WOT.
my suspicion is the spill valve, which I am leaning towards buying a used HPFP and switching my internals over but I hate guessing. Any thoughts?!
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you seem to be focused on it being something to do with fuel pressure, lean at idle and then is fine under load sounds like a vacuum leak
 
jdab555 said:
What intake size are you running? First log here is 2.5" intake, second log is up to 3" intake, both were taken at idle at the beginning of my tuning process. You can compare MAF voltage and g/s, looks like it may be low for what it should be in both columns.
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I am running a 3.5 jbr intake and hmmm I see now while mine idles around 2.4+ yours aims higher around 3+ g/s
 
jesus said:
I am running a 3.5 jbr intake and hmmm I see now while mine idles around 2.4+ yours aims higher around 3+ g/s
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Lookie here more logs - this is from way back in 2016 with my first Speed3, idle log with a stock-size intake on OEM MAF. Seems to show the same thing, g/s around 3 or up, but that may actually make sense given your larger MAF housing size. Probably one of the smarter people can chime in, but if you're at idle pulling in a similar amount of air over a larger diameter, your airflow velocity would be lower?
 

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chris' speed 3 said:
you seem to be focused on it being something to do with fuel pressure, lean at idle and then is fine under load sounds like a vacuum leak
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OK that’s a very good point. I’ve got tunnel vision for the fuel pressure because I’m seeing a similar thing with a AFR’s‘s, as I did last summer so I welcome the thought of it not being fuel related. I am taking it to my work tomorrow to try to troubleshoot the problem and hopefully get somewhere. And you’re absolutely right, a vacuum leak would bring more air into the equation and lean out the AFR’s‘s.
 
Nice to see one of us had some success, Friday night got around to putting a fresh set of injectors and seals since it was time to swap them out. In doing so i checked all my vacuum lines made sure everything was tight and nothing was bent or loose went ahead and even took apart the intake cleaned out the maf and did the whole run down. Still having the lean condition with low maf reading at idle. im thinking of going ahead and just buying the denso maf sensor and seeing if that helps out with the condition. On top of that might reach out to justin for a new maf recal and adjustment
 
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