2005 f 150 4.6 has -20% LTFT's revisited/ over reporting MAF/ (FINALLY FIXED)
- Patrickreaves
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here is what i am thinking at this point. ive read that at idle (700 rpm) that the MAF g/s should be about what ever the engine size in liters is, in my case it should be about 4.6. how ever my MAF at idle is .02 lb/s which converts to 9.07 g/s this number is 2 times higher than what it should be. so now i do a volumetric efficiency test .
MAF 258 g/s
IAT 118 degrees
RPM 4925
ENGINE 4.6 liters using a V.E. calculator shows a volumetric efficiency of 124% with these numbers. ( tested 3 times with similar results)
yet 80%to 90% V.E. is the normal range for N/A engines. so now im thinking my MAF is over reporting air intake by about 25% which i think correlates to the -25% fuel trims. since i have 2 different f150s, one with a 4.2 and one 4.6, i do some comparison.
4.6 liter
baro=14.9 psi
baro=160.04 hz
V.E.=124%
4.2 liter
Baro=14.4
Baro=156.97hz
V.E.=80%
I believe my MAF /baro reading on the 4.6 f150 is higher than normal which tricks the ECM into thinking that more air is entering the engine than it really is, with the fuel to match that air. hence the -24% FT.
it is said that a clogged CAT will lower the MAF reading due to restriction which causes the baro to be lower than expected, would the opposite be true if the cats were empty/hollow? that the MAF would read higher and air flow easier due to the less restrictive exhaust, i would think that it would alter the air flow and thus be skewed from the original air flow charts that ford programmed . but im not 100% sure of anything.
any advice and help is appreciated and if you need any info just let me know. i have a cheep scantool with live data and a vantage pro osscilascope.
thanks again
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Patrickreaves wrote: its said that a clogged CAT will lower the MAF reading due to restriction which causes the baro to be lower than expected, would the opposite be true if the cats were empty/hollow? that the MAF would be higher and air flow easier due to the less restrictive exhaust, i would think that it would alter the air flow and thus be skewed from the original air flow charts that ford programmed . but im not 100% sure of anything.
Removing the cats might improve VE slightly but it isn't going to bump a N/A motor up to 124%. Sounds like your MAF is over-reporting for some reason. Does the truck still have the stock air intake?
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- Patrickreaves
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I bought the (2005 4.6 f150) with an anti theft issue that was disabling fuel, starter,injection pulse and spark. I then went to a junk yard and found a (2006 4.6 f150) that had everything i needed to swap the PATS (passive anti theft) components, ( ECM- key w/chip- antenna coil that reads the key-and also the instrument cluster) as research says they are all programmed together. I put all the used parts into the 2005 f150 and it fired right up but with -20% LTFT on B1and B2. I have been trying to find the issue for about 3 years now. didnt want to be a parts changer but want this issue resolved so have replaced all kinds of components relative to the fuel trims in hopes of getting lucky , nothing has worked yet. yesterday i changed out 5 different MAF's that i got from the junkyard and reset KAM every time, with no changes
research says that changing the diameter of the duct that the MAF lives in will change your MAF reading. ex. a larger than factory intake duct will slow down air velocity and read less air, and that a smaller than factory intake duct will speed up air velocity and read more air. an expert said changing the bore size by 1 mm will effect the MAF reading.
With that, i believe i understand what you are getting to when asking if I have e changed my air box. and the answer is no i have not changed it, but bought the truck used and the previous guy could have. but from my trips to the junk yard it looks like its the one that belongs to the truck. i have even seen 5.4s from 97-2003 with the exact same air duct.
im going to measure the diameter of the MAF housing and compare it to other 4.6's at the junk yard. because your question is exactly what i was thinking, that maybe its the air duct thats skewing the readings.
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- Patrickreaves
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www.rockauto.com/en/moreinfo.php?pk=3469422&cc=1431301&jsn=519
www.rockauto.com/en/moreinfo.php?pk=4436106&cc=1432397&jsn=630
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- Patrickreaves
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but i believe that ford uses the same MAF sensor for the 4.2, 4.6,and 5.4 engines, (not 100%) so was thinking maybe the air box got switched out with a different factory box from a different engine. so i just went to the junk yard to look. The 5.4 ,2 valve and 4.6 have the same breather box and duct work from 97 to 2003. my 2005 4.6 has the exact same breather and duct as the years mentioned above. the 3v 5.4 is the only engine with a different breather box, duct, and a MAF (like the 2006 version you shared in the link in the above comment.)
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- Patrickreaves
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- Patrickreaves
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Patrickreaves wrote: thanks Matt ,no after market box of any kind.
but i believe that ford uses the same MAF sensor for the 4.2, 4.6,and 5.4 engines, (not 100%) so was thinking maybe the air box got switched out with a different factory box from a different engine. so i just went to the junk yard to look. The 5.4 ,2 valve and 4.6 have the same breather box and duct work from 97 to 2003. my 2005 4.6 has the exact same breather and duct as the years mentioned above. the 3v 5.4 is the only engine with a different breather box, duct, and a MAF (like the 2006 version you shared in the link in the above comment.)
You really need to either find an '06 4.6 truck or hit the O.E. parts catalog to find out what that '06 PCM will be programmed to work with. Pretty sure it will be different to the '05 and will require either an '06 intake system or a PCM reflash to fix this.
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Monde wrote: The MAF specs with key on, engine running is 0.46- 2.44v. Your MAF voltage is within specs. It seems to be reporting accurately. Something else is causing the rich condition. Can you find the maf voltage specifications to compare it with mine? I got mine from mitchell.
The '05 MAF appears to be working properly but the '06 PCM isn't interpreting it correctly. VEs over 100 means the PCM is seeing more airflow than the engine can physically pump.
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- BetterCallBrody
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- Patrickreaves
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how ever my intake is all aluminum and is probably twice as high as the plastic one. i remember trying to research when ford revised the intake and was unsuccessful as it wasn't that important at the time. i will now resume that research . below are pictures of the two intake manifolds
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- Patrickreaves
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And the aluminum one is the one I currently have on my 2005( manufactured in 2004) f150 4.6.
As suggested above maybe there is a difference in the transfer function table in the micro processor between the two different engine computers, and thus causing the issue of the over reporting MAF sensor.
but at the same time, i am in mustang and f150 groups on face book , and there are a lot of people opting to swap out there intake manifolds with that of a ford windstar as it supposedly has the best intake. i wonder if they had issues like this. what about people that put the P.I. heads on non P.I. engines, surely doing any changes would cause air flow velocity issues.
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- Patrickreaves
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Monde wrote:
Patrickreaves wrote: Ok here are some captures with engine warmed up at idle (650rpm)
The MAF specs with key on, engine running is 0.46- 2.44v. Your MAF voltage is within specs. It seems to be reporting accurately. Something else is causing the rich condition. Can you find the maf voltage specifications to compare it with mine? I got mine from mitchell.
I watch a lot of "ford tech makuloco channel" as he is a ford tech works on these fords and provides lots of content like scanner danner does. But he says that the maf spec should be .75 volts at idle and up to 4 volts WOT. but have not confirmed this spec with any other source.
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- Patrickreaves
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BetterCallBrody wrote: If you had access to HP Tuners or SCT you could download the file and compare the table to a known good stock one to see if its stock, maybe the '06 had a tune on it.
as far as a tune on the 2006 ecm, any thing is possible. I dont know how i could tell if it has one or not. My cruise control does not work because the 2006 ECM was on a plain Jane XL model that doesn't have cruise control, while my truck is an XLT and does have cruise control. with my scan tool if i put the original ecm in i can actually test the buttons functions on my steering wheel, and they all work. they do not with the 2006 f150 XL ecm installed.
i have got some quotes from lock smiths to try to fix the anti theft issue, $180 just to make a chipped key. and i have to have 2 keys to program it.
But then im also worried that its the ecm that is bad and not the key. it just sounds like a $1000 repair that i cant do myself. even worst would be getting the anti theft issue fixed only to find -20% fuel trims in the end lol . what i can do is find a junk yard ecm from 2005 with the same configuration as my truck.
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- Patrickreaves
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My fuel trims are now
STFTB1 = +/- 5%
STFTB2 = +/- 5%
LTFTB1 = 0%
LTFTB2 = 0%
my MAF voltages are still the same , however my new grams /second reading at 4800 rpm = 177. V.E is now 85% and the old readings were = 254. grams/second @ 4800 rpm. V.E.=124%. It must just be the way its interpreted by the ECM that was different, just as Matt suggested. So great call on his part. I have literally been chasing this issue off and on for 3 years. so just want to say thank you to Matt, and Mondo and everyone who made comments and suggestions. I am very happy to have this issue resolved. And my cruise control works for the first time also.
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