In this video i am diagnosing fuel trim numbers along with a dirty MAF Sensor. During the process we will find out that the dirty Maf sensor was not the only problem on this vehicle.
clearing DTC does not reset the fuel trim numbers, the reason you got worse numbers after cleaning is because the maf sensor was wet and cold, it takes a little time for it to warm up and dry, you could actually see that when you raised the rpms after the cleaning you started to get negative fuel trim numbers which means it was getting better and if you just would have taken the car out for a 10 minute drive the negative short term would lower the long term fuel trim
Just bought a 2003 Lexus ES 300. Was having trouble with too rich lean codes. I would step on the gas and around 2500 rpm it would max out at 52.3% Long Term FT on both Bank 1 & 2. Luckily I had my own scan tool and figured those specs would be the same for the Lexus since it was an 03. I had “cleaned” the MAF and the throttle body prior to watching your video. I noticed on the MAF sensor you showed those heater coils. I didn’t clean those. Sure enough the top one was dirty and when I disconnected the negative battery to reset the codes I was running dead on the spec sheet you showed. I couldn’t be happier. I was thinking it was my Bank 2 Sensor 1 A/F Sensor, since it kept showing p02198 as well as p0171. Thank you!!!
Yep, it's within spec of the +/- for 10 %. If it's a high mileage vehicle, I would definitely be OK with those numbers. In my experience of being a mechanic for years, it's hard to get them to null out to zero, unless it's a newer vehicle. My 2001 S-10 4.3L with 170,000 miles hovers between +6 to -2 total trim on both banks. My fuel pressure is fine also as I put my gauge on it to test it( after I put a new pump in it a while back, and fuel filter, along with new intake manifold gaskets upper and lower). Mechanical wear in the engine plays a part in this, as the tight tolerances open up over time and cause higher than optimal LTFTs. My rule of thumb that I use on all the vehicles I work on, is that if the total fuel trims are between +/ 10%, I leave it alone.
Great video Eli, I'm learning fuel trims problems, these videos are very helpful to me, and I appreciate you make them, thank Eli, hope one day we meet personally, cheers from ontario ca,
Great diagnosis and video content is very good as well. Having 2 banks helps diagnosis a lot, you know already that it is not the fuel pump since one bank is working good. Well done and thanks for posting mate!
Can u give me the specs or tolerances for my vehicle for live data? Maf is 0.04 engine off and 0 91 lb/min at idle. New filter tries cleaning maf without brush
Amigo, there is a difference in NORMAL and IN RANGE, normal is floating around zero to + - 5, in the range is as high as 20 while the STFT is still active if the LTFT and STFT both max out then this is out of range and other codes will be set. Any LTFT is compensating for a problem with STFT but the computer can handle it. A partially clogged exhaust can also cause these same types of readings. MAF g/s should typically be 1.1 g/liter (or a little higher) of the engine so 3 liter is about 3.3 g/s. A larger item collects more dirt. I think one is the MAF and the other is a temp sensor. Don't clear codes, LTFT takes time to normalize, you need to do a test drive. FOR EXAMPLE, if you or a tech does not fix a problem, the next tech wants all the info he can get so pls don't just erase it, pass it on. In this case, you are correct to look for an additional problem. Thank you for showing before and after cleaning the MAF but it does not seem to help enough. As we can see, after loading the engine the LTFT went back up, this is why you should not erase codes, the MAF was fixed, the computer would learn the new strategy on its own. Now there is no MODE 6 data for the next guy if needed and all Monitors have been erased and some take days to re-run so if you live in a SMOG State, your customer is screwed for Emission Testing quickly. The vacuum leak only needs a small increase in RPM and it's mostly noticeable in STFT, I don't see that here near the end of the video. You are still lean on bank 2, I think you need to clean the injectors and I would need to see O2 sensor activity to give a better answer about valve adjustment or other minor problems. It's not MAF (affects both sides) and it's not vacuum on one bank, not at that RPM. How many cats as the actual code is for a cat, are there two or does bank 1 and bank 2 joint to a single exhaust. P0420, need to watch pre O2s and post O2s for a better picture. Thank you very much for this Case Study, very good at showing before and after diagnosis. It is 2021 now and I am very sure you have a lot more experience. I will go look for PART 2 if you have one. Mucho Gracias.
Where did u get the spect print out?? I'm having a similar issue on my is250. But I think I solved my issue this morning. It seems that my new toyota MAF does not fit snugly in the air intake tube, those creating a small vacuum leak. I switch back to my old sensor and BAAM! My fuel trims went down from 20% and 30% respectably. To about -3% and 6%.
@@EliTheOBDTech I had recently bought the car and wanted to start out fresh knowing that I had done a much needed maintenance on it. I replaced all 4 rotors and brakes. All fluids, Wipers, spark plugs, plug wires, vvt oil sensors, air cleaner, MAF, EGR valve, O2 sensors,. I've also did a complete air intake cleaning all the way down to the valves removing as much carbon from the top of the valves. I also added a oil catch can. Soon there after I started getting the check engine light on and being that I was not getting a Code for bad MAF but rather a rich condition bank one, I figure it had something to do with fuel regulator or a vacuum leak. But not a bad MAF. Ur videos help me a lot understanding the long term and short term trims. I never would have suspected that it was the actual MAF housing that was causing the vacuum leak. Thanks again !!!🤗🤗👍👍
FYI.... not all manufacturers provide parameter data values. In this case, Toyota does. This was obtain from a automotive service repair program called AllData.
Great video ! Thanks for the info, I didn't know that you have to disconnect the battery to reset the computer, I thought by only clearing the codes will be enough, I had different results by disconnecting the battery, THANKS again.
In some instances like Toyota/Lexus you have too in order to clear fuel trim memory. Second option would be driving your vehicle 50+ miles in order to relearn new fuel trim parameters.
So I got code p0171 but my lg term trims are stuck at 14.1 and 13.3% it doesn't not change no matter if I rev it to 3krpm. I help it for a min and the lg term on both banks stayed the same. Could if still be a bad maf?
Nice video Eli TheOBDTech. I have a 2002 Toyota Camry XLE V6 3.0 Liter 1MZ-FE engine. The engine stalls at idle on occasion when I stop at a traffic light. It will stay that way until I get to my destination ant turn it off for a while. Then it works fine when I drive it again. It can go a few days or a few months before it happens again. I have cleaned the MAF sensor a few times with the CRC Mass Air Flow Sensor cleaner but have not used a brush as you recommended. I have also cleaned the throttle body. There is no check engine light or any codes with the scanner. Can I use the same data sheet from this video, as it appears to be the same engine. Any thoughts on this issue?
hello. SHRTFT1(%) = +6.3 and LONGFT1(%) = -7.0 , is good or bad? Another question: SHRTFTB1S1(%) = 2.3 and SHRTFTB1S2(%) = -100.0, is good or bad? what does "G"?
I'm lost on my 2003 ES300. It has sky high LTFTs at idle suggesting a vacuum leak. I just changed the spark plugs. I know for a fact it wasn't like that before the plug change. I changed the intake gasket. I checked every vacuum hose. I went around all the hoses and the intake with propane. No change in RPM and the RPM is in range. I did the same with starting fluid. No change. As I raise RPM the LTFTs drop. At idle they are close to 30%. I don't get it.
Check for brake booster vacuum leak. Best method to eliminate vacuum leaks, use smoke machine. Check your upstream O2 sensor data on a scan tool. Check to see if it's fluctuating from rich to lean.
on Same throttle position, dirty MAF Sensor will notice lower Air mass, compared to Cleaned Sensor. More air means need more fuel. Thats the logic to get proper AFR.
Hello. How can I get a spec sheet for my vehicle? I have noticed gas mileage getting bad and I have no check engine but my long term fuel trim is kind of high.
Hi Eli - thanks for the great video! I have access to Alldata,, but can't seem to find the data sheet that you use in the video. What area should I be looking in? Thanks!!!
Hi Eli - Thanks for the quick reply! I finally found it! You had given another poster a ballpark location, and I just poked around until I finally found it! This is such useful information. BTW, the vehicles is: 1999 Mercury Sable Wagon / 3.0L Duratec DOHC 24-valve - automatic. I have a free ALLDATA account through my library. Usually you have to go into the library to use it. Anyway, the path through ALLDATA is as follows: After login - choose the REPAIR (blue box) [Under SYSTEM and COMPONENT banner] POWERTRAIN MANAGEMENT [Under COMPONENT banner] COMPUTER and CONTROL SYSTEMS [Under TESTING and INSPECTION Heading - Right side] SCAN TOOL TESTING and PROCEDURES Normal Scan Data Values - Includes PIDS - takes you to the values
@@EliTheOBDTech awesome! Thank you very much for the reply. I am trying to learn as much as I can about this stuff. I appreciate you sharing your knowledge.
@@dm7097 Then you can learn something more: never spray anything at all on O2 sensor connectors. They work with reference air and they pull it from the sensor wires. Spray anything (such as MAF sensor cleaner) on them, and the ECU begins reading always lean (very low voltage) until you replace the entire sensor (expensive stuff). Don't make the same mistake i did (well, O2 sensor was due for replacement anyway in my case since it was very very old and was also replaced with an updated part).
I have 1500cc petrol engine in toyota ...... I tried two maf sensor one giving 1.3 g/s at 650 rpm.... Another giving 1.7 g/s at 650 rpm.... Which one should i use for better fuel economy.....plz reply
Normally, you want a MAF sensor that is closest and slightly over the size of the engine. In your case 1.5L engine, you want the one that is showing 1.7 g/s. Ideally your MAF reading should be 1.5 - 1.8 g/s at idle.
When a MAF sensor is under reporting is usually due to a vacuum leak or some type of internal leak. Intake or exhaust valve sealing problem or dirty MAF sensor.
How do I get that paper you have for my 04 BMW 325xi 2.5l sedan awd I have not change my maf sensor I've tried cleaning it but don't change and I have p0420 also can that cause rich condition
My Long trim b1 and b2 is stuck on 100% short trim is stuck on 70% with lack of power can't pass 2,500 RPM with p0300 code now what do you think I clean the MAF sensor the car shakes when I unplug MAF sensor car runs good
There is chance that your MAF sensor could be the problem, but I'm thinking that you may have a large vacuum leak. Does your fuel trims drop if you raise the rpms?
@@Tootoojackson I'm glad you fixed your problem. That is the usual symptom of a Faulty MAF sensor, it will prevent you from going over 2500 rpms. Very common on Nissan vehicles.
@@EliTheOBDTech thanks for your help also I have one more question if you can help me with my ho2s2 mntr b1 and b2 is running lean what you think that should be spark plugs or 02 sensors
good video the only thing I would do different is when using the phrase "fuel trim" always specify "Long term" or "short term" because they have different functions.
Hello, excellent video! A little question, may be you can help me, what means this values?: At idle (LTFT +10% , STFT -4 ) At 2000 rpm (LTFT 0%, STFT 7%) At 3000 rpm (LTFT +4, STFT +4) My mileage is very bad!!
Yes, but at 3000 rpm, your ltft increased to 4%. When fuel trims tend to fluate, it is more likely a MAF sensor being dirty or fuel delivery problem. I wouldn't rule out a potential vacuum leak or a lazy upstream o2 sensor.
Cool , but could it be a vacuum leak that,is,making the numbers go rich ? Did you get to make a another video on it? That is strange no code . Thank you bro.
***** I do suspect a vacuum leak only because the fuel trim numbers are positive and tend to drop when applying a higher rpm. At the same time i also think the vehicle may have restricted injectors due the fact the fuel trims would fluctuate during certain rpm range. No, I have done another video. Customer will bring it back when the vehicle throws a code.
David Usually a vacuum leak will tend to drop long term and short term fuel trims under load to normal values. If that happens that is usually an indication of a vacuum leak.
Although I did not record the fix for this vehicle, the culprit problem was a cracked intake hose and couple of cracked vacuum hooses that connect to the intake manifold
I have negative values. -18 ltft and -12 stft at idle. throws code p0172. car is mazda cx7 2.3 turbocharged. already replaced maf sensor. still same problem. please HELP
Assem Karhani It could be many things that affect your air fuel ratio. Since you already replaced the MAF sensor, you can scratch that out. Other possibilities: high fuel pressure, leaking fuel pressure regulator, defective upstream o2 sensor on bank 1, clogged air filter, leaking injectors on bank 1 and perhaps need valve adjustment on bank 1 if applicable on that vehicle.
@@EliTheOBDTech Thanks! I went to www.alldata.com/ and it seems to be subscription based and would benefit shops. I also went to alldatadiy.com/, but it doesn't have my 2016 MINI in the list.
@@Charkatak FYI, actually not all Manufacturers provide normal data values, usually most Asian and Domestic manufacturers do, it's vary rare in European vehicles.
@@EliTheOBDTech Understood! Just wanted to see the normal readings for my vehicle to diagnose MAF sensor failing idea. I couldn't find Bosch MAF sensor datasheet for my 2016 MINI Cooper S 4 dr Hardtop model.
Eli TheOBDTech thanks I have a 1999 Honda Accord EXL 3.0 V6 and a 2007 Honda Odyessey 3.5. Really appreciate your quick response. My Email is ajfricchione@optonline.net. Thanks again really enjoy your videos
Eli TheOBDTech gtblender863@aol.com , thank you! My car is revving up and down on idle and also when driving in a repetitive way and I need to find out what part is bad, iac is cleaned, i don't know what it is and cant really afford a mechanic right now..
Amazing Video. Could you send me the data sheet on my 2014 Ford Mustang 3.7 Engine V6? I am having sputtering, loss of power with no codes and weird fuel trim data. Thanks :)
Eli TheOBDTech generic OBD2, I thought since it’s near -100 that car might be running rich. Ford says I need a new cat but idk what caused the cats to go bad. There is a jerk between 15-30 mph as well.
@@Oleapeps perhaps the jerk is due to the pcm subtracting fuel due to a rich condition. Negative fuel trims are usually caused by leaking injectors, leaking fuel pressure regulator, restricted air filter, high signal on the egr valve or faulty oxygen sensor stuck on rich condition 0.8v+. And yes, sometimes a faulty or dirty MAF sensor will cause a rich condition.
How come no one checks the air filter? that dirt on the MAF is coming from somewhere and a dirty filter would cause a low reading at the MAF wouldn't it?
Unfortunately the air filter can filter up to a certain particle size and no better. So anything smaller than what the filter can stop from flowing to the MAF, flows through and cakes the MAF in dirt over time. That's why it should be pulled out and cleaned up with quick drying contact cleaner every air filter change... but most people just don't give a fuck. Yes, dirty MAF sensing element brings MAF reading down and LTFT up.
@@EliTheOBDTech Hi Eli! Great video! Thanks! Do you have the specs for Subaru Outback 2.5 2005? I would appreciate if you can share. My email is sedautov@gmail.com
Hi Johnny, you will have to forgive for not sending the spec sheet today. I'm off with my family on this long weekend. Sorry for the delay, expected by Monday. Happy Thanksgiving.
Vehicle had contaminated dirty maf sensor with vacuum leaks. Cleaned maf sensor and replaced few vacuum hoses along with cracked intake hoses going to the throttle body.
@@jb6574 in this video i did not show my visual inspection of broken or brittle vacuum hoses. Any time your fuel trims start high and decrease as you increase your rpms, that's indication of a vacuum leak which affects your MAF sensor readings. This vehicle had a combination of a dirty MAF sensor and vacuum leaks.
Eli TheOBDTech I guess what I meant is without vacuum leaks how did you know it was maf and not fuel related since fuel trims that get higher with increase rpm can indicate either a fueling issue or a sensor issue
@@jb6574 This vehicle did not have faulty MAF sensor, it was just contaminated with debris. By cleaning it up, it solved that problem. The biggest issue was vacuum leaks. MAF or fuel related problems tend to show up with low fuel trims and then an increase of fuel trims as you raise your rpms. In this scenario, I removed the MAF sensor and I did a visual inspection to determine if the resistors were dirty with debris.
Low fuel trims that increase when you increase the rpms, dirty MAF or fuel delivery problem. High fuel trims that decrease when you increase rpms, vacuum leak. This vehicle had both problems. Vacuum leaks and dirty MAF sensor.
Higher long-term furl trim most of the time indicates a vacuum leak because the computer is adding more fuel to compensate for extra air getting into the system. Complete opposite of what you’re saying.
