In the article about "Fuel Syatem Too Rich" there is a section on determining if the MAF is faulty. Part way down the paragraph, the statement is made.... (These conversion tables will help.) The conversion table are for calculating Barometric Pressure for elevation. Where do I find these conversion tables? I need to evaluate the parameters of my MAF to see if it is faulty because I keep getting a P0171, Too lean code and I can not find any vacuum leaks. Thank you
My question is where do I get the conversion tables mentioned in the article? on 1999 Toyota 4Runner
by DRMILLAN in Green Bay, WI on September 05, 2012
1 answer 6 comments
ANSWER by pushrod on September 06, 2012
WHILE MAF CAN CAUSE THIS, SO CAN A LOT MORE STUFF. MAP SENSOR,FUEL PRESSURE LOW, PCV VALVE, 02 SENSOR,INJECTOR(S) AS YOU MENTIONED VACUUM LEAK. DO YOU HAVE A SCAN TOOL THAT CAN STREAM LIVE DATA? AS FOR BARO. PRESS. READING CHECK THE WEATHER CHANEL, TYPE IN YOUR LOCATION.
COMMENT by DRMILLAN on September 09, 2012
Thnak you for the reply. As for the barometric pressure, I was assuming that the way the article mentioned a conversion chart, that there would be a way to take the baro pressure in my area and do a calculation to see what my MAF should be reading. I do have a Snap-On Modis scan tool. EVen though I am not a mechanic by trade, I do know a fair amount and when I came across a MODIS w/lab scope updated through 2009 for $800 and 6 months to pay, I couldn't pass it up. O2 sensors were replaced about 2 years ago and do not seem lazy. PCV is 6 months old and is clean. I do have a suspicion of a fuel pressure issue even though the fuel filter is also about 6 months old and a WIX, since I am getting intermittant bucking/hiccup-like jerks while driving as if the ignition or fuel were being switched off for a split second here and there. LTFT is usually at 39.8 while driving and sometimes will drop to 17.3, but is rare. STFT bounces like normal from as low as -8.3 to about 8.3, but likes to stay in the -3.7 to 3.1 range. 4Runner has 226K miles and my first sensor, other than the fuel sending unit which has been crazy for the last 3 years, just went out. It was the TPS, and weird thing is, the bucking started about the same time I replaced it. I used the brand "Standard" for the replacement part, the company is reputable, but I suppose I could have gotten a bad one. Seems to hold constant voltage at idle. Even with a MODIS, the live data from the TPS is a good 5 seconds slow to the scanner. I need to figure out how to check my fuel pump wave form on the lab scope portion of this tool. There is a way to show a split screen and compare it to a known good wave form, but I don't know how to do this yet. A low amp probe sure would be nice, but $350 from Snappy....ouch! Correct me if I am wrong, but other than maybe an exception or two, don't vehicles have either a MAP or a MAF, not both? I have a MAF, and I do not see any other sensors along the intake, so I am figuring that it has a built-in AIT. I only use shit-free, ooops, I mean ethanol-free fuel, except wehn I am somewhere that I can't find it and am in dire need of fuel. I hate that crap. Scientific fact, Gasoline = 125,000 BTU/gal, Ethanol = 84,600 BTU/gal. Tell me again why it is better? I like the ad that says NASCAR is using ethanol and getting more horsepower, oh yeah, it is sponsored by "The Corn Growers of America" I also use a can of Amsoil PI 4 or 5 times per year, but that doesn't gaurentee that my injectors are dirt free.
IF YOU HAVE A MODIS THEN (WHAT A DEAL FOR 800.) CHECK TPS SWEEP FROM CLOSED THROTTLE TO WOT. MAKE SURE IT DOESENT DROP OUT. I KNOW ABOUT THE LEAN CODE ON BANK ONE BUT HAVE YOU DONE A GOOD TUNE UP ON YOUR TOYOTA? I MEAN A COMPLETE TUNE UP. HANG IN THERE WITH YOUR SCANNER AND YOU WILL FIND THE TROUBLE. GO PACKERS, AT LEAST NEXT TIME!
Interception from Rogers during a comeback, that was rare, but early in the season. Oh well. Define a good tune-up. I did plugs, the three wires from the coils over, PCV, sprayed the MAF w/CRC MAF cleaner, washed and re-oiled my K & N air filter, sprayed the throttle plate clean, and put a new WIX fuel filter on about 6 months ago. Even if the TPS does not drop out, can it have a bad spot in the normal highway driving spot?
NOW, ARE THE COILS OE? IF SO TRY THIS, BUY ONE NEW ONE, PUT IT ON SAY #2 CYL TEST DRIVE IF PROBLEM STILL THERE CHANGE IT TO #4 SO ON OR LOOK VERY CLOSE AT COIL PLUG BOOTS FOR CRACKS. YOU SAID K&N FILTER, MAKE SURE OIL HAS NOT ENTERED MAF FROM OVER OILED FILTER! I CAN'T REMEMBER IF MODIS DOES MISFIRE DATA ON THIS ENG. IF SO DRIVE WITH SCANNER HOOKED UP. ALSO CHECK FREEZE FRAME DATA. IT SOUNDS LIKE YOU MAY HAVE AN OLD FASION MISFIRE. LET ME KNOW HOW IT TURNS OUT. GOOD LUCK! IF YOU CAN TELL WHICH CYL IS MISSING THEN SWAP COIL TO SEE IF MISFIRE FOLLOWES COIL.
This is what I am not understanding. It has intermittent chugs or bucks, but does not trip a misfire DTC. Unfortunately I do not have a specific misfire section for this vehicle with the software provided. Under "DATA" there is a list of cylinder 1-6 for misfire but I think it is only to tell me if there is a misfire DTC and not real time misfires. I'm pretty sure that an $1,100 software update for the MODIS will provide the misfire specific data screen. I do know which one you are speaking of because my friend Jeff has that display on his MODIS. I asked the dealer about it and he said it is a matter of an update. Maybe I can borrow his and take it for a drive and use the misfire data screen under driveability. My MODIS does not even offer a "drivability" menu. I'll have to look to se if I am running 9.4 or 11.2 software.
While in misfire data screen 1-6 if it will misfire enough it will show which cyl. But have someone ride along and look at misfire data. I still suspect coil! Don't know why, just a hunch.