MAF tastic

[troyboy162]

I might be a little premature writing this as I have not tested the fix for more then 30 minutes of driving but I wanted to get the details down

My truck lost power going up a hill 5 hours into a 8 hour drive last week. I pulled off onto a secondary road and it began studdering and barely able to drive 20mph on a flat road. It was a 100 degrees that day so my trouble shooting was not a strong game. The truck could idle smoothly, but would pop, sputter and even backfire when reved up by hand. I thought I had lost another fuel pump since the symptoms were similar under throttle. It finally gave a P0125 code, but in that last troubleshooting effort I re-seated the maf connector(and tapped on the maf), checked a coil for oil down on the spark plug and disconnected the upstream O2 sensor for the P0125 code. The truck then ran but was significantly down on power. It felt like it was missing a 3rd of the horsepower.

I figured this power loss was due to running without the fuel tuning provided by the O2 sensor, but a new sensor did not fix it.

I thought then that I had melted the cat while the fuel ratios were off and plugged my exhaust, but a local guy showed my the inlet and outlet temp of the cat were correct (indicating flow and correct function of the cat).

I talked to a mechanic buddy and he said that barring some horrific vacuum leak... 1) Maf, 2) Split woodfuf key on timing belt, 3) coil, 4) plugged cat were his ideas in that order (or a combo) given the info of the problem and the ongoing power loss

Yesterday it gave a code P0171 and Ive never been so excited to get a code lol. I tried my friends MAF and the truck had all the power back.

After a few weeks of daily driving on a junk yard maf, ill call it good. BTW a new OEM maf is $750 right now for a 96-98. Swapping to a 99-02 MAF and air box would be far cheaper.

[YotaFun]

Great find with the MAF!

Also could not agree more with the 99+ style air box and MAF, I have one sitting in the garage waiting for me to do on the long list of things to be done.
And with junk yards becoming more plentiful with our trucks (at least around here -_-) should be easier to find the whole set up cheap.

I will try to find the write-up and post the link, I know when you do the swap I believe there are two pins that have to get swapped in the connector for newer style to work in the older trunks.

[troyboy162]

I noticed the parts getting more plentiful the last couple years. They stayed out of the junk yard for a good long time, but now its starting to get better for guys like us haha.

I read about de-pinning that connector to make the swap. That sounded hard. I might have just soldered the wires where they needed to go.

I got out ok with a $50 maf from the junk yard. It did however throw a P0171 on me yesterday, but I was out pegging the truck testing power. I've read that may cause a P0171 during the computers learning phase...hard to say, but its making good power again so I have moved in the right direction.

[4x4mike]

$750!!! Man, I had no idea they were that much. Good on you to be able to get one for $50.

I carry a used coil pack, MAF and TPS that I bought for pretty cheap from DeathCougar. He parts out 3rd gens on a regular basis and after a trip to Pismo, where our caravan had MAF and coil problems, I thought I'd pick up some parts.

[troyboy162]

The $750 price is nuts. I think it probably means there are no more in production from Denso. Chinese clones are available with the denso stickers on them so those are bound to start making it into the market soon.

Still getting P0171 every few days. Total of three now since last thrusday and the last code came up on a normal hill climb and not a full throttle assault sooo...I'm doing the 99-02 airbox swap. Could be a few other things of course, but since ive never had a P0171 I suspect the 21 year old, junk yard maf, also has this common failure.

I figured I would do a updated write up on the details. Its not a hard job but the info is spread over a couple forums and the pictures are disappearing. Is yotatech the best place to post tech info these days? I like this forum, but its not being maintained anymore.

[habanero]

A write-up would be awesome for repinning for those of us who will likely be following in your footsteps one day. Dunno where you'd put it, here, t4r or yotatech. Be easiest to find here or YT, busiest on T4R.


A little aside...
I have a little post on testing the maf in the 96 with a link to info I used on ncttora and info I found on UY (I think, for some reason I didn't give credit, darnit). Link's no longer any good...
For those with connectors like my 96 has and for my own future reference since they are not the same as described in the ncttora link:
http://i4.photobucket.com/albums/y141/smcr/MAFpin.jpg
for air temp...use ohmmeter
unplugged, neg lead to E2, positive to THA
k ohm
2.2 - 2.7 @ 20 degrees celcius
.5 - .7 @ 60 degrees celcius
Don't know if it's kosher or not, but I used a hair dryer set on low and not too close to raise the temp and see what happened. It appears to work nicely

http://i4.photobucket.com/albums/y141/smcr/mafconnecter.jpg
For air flow....use voltmeter
plugged in, ign on (not running)
neg lead to VG, pos lead to E2G
looking for voltage fluctuations when air flow is introduced (blow in it, already). Again, worked as it should.

[troyboy162]

got it all together and it runs better then ever, yet I got a P0171 while idling after a hill climb on the maiden voyage. Not sure what to make of that, but it looks like it works anyhow. there isnt too much feed back from success stories out there.
Hopefully the codes go away, but if they dont, my first guess wont be this maf. Its really running very well with it.

[YotaFun]

Time to get some throttle body cleaner and spray some vacuum hoses down and see if you have a leak anywhere...

[troyboy162]

I found some vacuum leaks earlier and fixed them and it made a little difference, but I uncovered a larger problem in that my long term fuel trims were very high across the board and short term were also high.
I'm looking into fuel pressure now...I'm still trouble shooting...

[troyboy162]

weak fuel pump replaced. lol now I dont know if that fuel pump flaked a few weeks back or if it was the maf. At least I understand fuel trims and maf readings so I can diagnose whats going on better.

follow up on the 99 MAF. It definitely makes the truck run better then my junkyard MAF. The fuel trims do adjust richer for it at idle so the value is not exactly the same as the 96-98. The trim difference goes away pretty much during driving though and that backs up the compatibility.

[troyboy162]

Write up finished over on TTORA
http://www.ttora.com/forum/250-late-4runner-tech/237857-96-98-maf-upgrade.html

[4x4mike]

I uncovered a larger problem in that my long term fuel trims were very high across the board and short term were also high.


Do you recall what your numbers were? I've never really tracked my numbers but my Ultra Gage reports them. At highway speed I'm showing Short: 0.78 and Long: 3.91. At start up with a cold engine I'm showing Short: -7.8 and Long: 0.00.

Edit: I just read the write up for the numbers. Thanks for the info.

[habanero]

Awesome easy write-up, hoping I don't have to utilize it for a long time, but will be very thankful when it's time.

[troyboy162]

Do you recall what your numbers were? I've never really tracked my numbers but my Ultra Gage reports them. At highway speed I'm showing Short: 0.78 and Long: 3.91. At start up with a cold engine I'm showing Short: -7.8 and Long: 0.00.

Edit: I just read the write up for the numbers. Thanks for the info.

I started out at +29.7 across the board for long term trims and I believe that's as high as they will go. Short terms were 5-29 as well so it was trying hard to get fuel. Oddly there was no sputtering or anything I have experienced in the past. I think my the old plugs and wires I used to have would compound the fuel issue and give me the surging, sputtering when a pump was crapping out. Yup...This is my 4th pump in 4 or 5 years haha. The last pump had all the updates on my fuel tank plumbing so I dont know why it died. It should have lived a very happy life. Hopefully it was just a bad pump to start with. After my third Delphi pump, I can say for sure that they don't have tight tolerances. Each one has sounded significantly different then each other.


Awesome easy write-up, hoping I don't have to utilize it for a long time, but will be very thankful when it's time. Thanks! I hear ya, when its MAF time its no fun. I dreaded re-pinning that connector. Turns out wrestling with my intake tube is the hardest part.