MAF Sensors
 

My car randomly goes into limp mode when starting her up (I’ll shut her off and open the driver door and this always takes out of limp mode) and I get the MAF sensor code on the obd 2 scanner.

I was able to get around cleaning both MAF sensors tonight. For the two screws per sensor, I noticed they had to be “broken” off loose (they made a snapping sound right before being able to turn them loose). When putting them back on, do they have to be tightened to a certain point? Or as long as it’s on there good, should it be okay? I’m asking because I didn’t notice any gaskets and didn’t want to experience a vacuum leak. I def. won’t be using a Philips head driver in the future, as the metal seemed soft and borderline stripped the top of the screws.

There is some stiction between the metal screws and the plastic housing which causes the pop when you break them loose - it's normal. There should be torque specs in the FSM but I just got mine "hand-snug" and called it good.

The FSM says the screws for the MAF sensor should be torqued to 1.47 Nm or 13 in-lbs. That is extremely light, so its easy to overtorque.

Two of my favorite members of this forum. Thank you both! :tiphat:

Also, if I over-torque the screws, any consequences? Can’t imagine getting the system getting a false read from this lol

You're liable to break something. Make sure the MAF flange is square with the duct flange and snug up the screws. If you don't have a torque wrench, you can rent/borrow one at most auto parts stores. Once you've done it with a torque wrench, you should be able to get close enough by hand.

For those low torque settings a Fat Wrench works great.

https://www.wheelertools.com/gunsmit...iAAEgKNzfD_BwE

So the paranoia got the best of me, and went to unscrew the bolts and lightly tightened by hand with a Philips head, almost to where I could probably unscrew by hand if I tried really hard.

Took her for a spin since I had the garage door open. On a side note, the can stated cleaning would result in a 4-10 hp gain at the wheels, which I find hard to believe. Someone on a youtube vlog, who also stated they were registered on this forum, also said their car felt faster. Perhaps cleaning the MAF sensors gives you the original power back from when it was first built, and not an actual power gain?

You got back on what you lost. You didn't gain any.

What was the exact code?

I don’t recall the exact P code, but I do remember it saying “MAF sensor” at the bottom of the scanner.

Even after cleaning both MAFs, car still goes into limp mode, which leads me to believe I will need to clean the TBs.

Just be careful cleaning them.


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I am actually really hesitant/nervous about doing it. I read that it's not part of the recommended maintenance item, and done extensive research about it on both this forum and the G37 forum, and seeing mixed information/stories about cleaning them.

I'm reading from some people are disconnecting the battery, while others don't and that disconnecting will require the relearn procedure; to the relearn procedure not being necessary; to moving the butterfly will mess up the ECU's calibration; to replace/not replace the o-ring, to leaving the TB on/take then off when cleaning, etc.

I've seen youtube videos and seems like a straightforward process, but the differing/contradictory information is what's stopping me.

Don't worry about all that. Just disconnect the negative battery terminal if you're at all concerned. I've done it on a bunch of 370Z TBs all different ways: with and without the battery connected, with and without removing TBs (o-rings looked good and didn't need replacement) and always lots of butterfly valve movement to get the back side clean, especially if you leave them installed. Never had an issue other than needing to relearn the accelerator pedal position, which is super easy.

Liberal use of the right cleaning products (MAF cleaner and Throttle Body cleaner) will be just fine. Use a stiff bristle brush to aid in the cleaning process (only on the TBs, not on the MAFs).

I cleaned my MAFs several times and it was VERY easy - if you can use a screwdriver and a spray can, you can do it. The MAFs are not particularly fragile - they can stand up to the environment under the hood - but you don't want to bang then around. Do not poke the cleaner straw into the MAF body; there is a thin wire that you could break if you make contact with it.

According to what I've read on this site, cleaning the TBs is a more complicated job but still pretty easy (see JARblue's comment above). There are several threads explaining the procedure.

As usual, good info from jarblue and southark370z!

Cleaning the MAFs was really simple. I actually sprayed down and waited about an hour to ensure it was fully dried.

I will be moving forward with the cleaning of the TBs, just a matter of finding time.

In preparation to clean out the TB's, I bought some updated torque wrenches (the ones I have are old and are probably in need of calibration anyway), including an inch/pound torque wrench, torx wrenches, and updated allen wrenches. I also even got dielectric grease for the battery post/terminal for when disconnecting and ordered new O-rings for the TB's. Just had a few more questions:

1. I read that the job will be much easier if I remove the engine strut bar and engine cover. Does this need to be taken off even if I am taking off the TB's themselves?
2. This one is for Jarblue (and anyone else with experience) - earlier you mentioned that I could move around the butterfly valve when cleaning, and it wouldn't be an issue when re-installing?
3. This one is also for Jarblue (and also for anyone else with experience) - other than the possible relearn of the accelerator pedal position, is there any other relearn procedures I will have to complete?

1. Yes. Removing the strut bar and engine cover will make it easier regardless of whether you remove the TBs or leave them on.

2. If you're worried about it, just disconnect the negative terminal on the battery before moving the butterfly valve. I've done it both ways without issue.

3. There are two other learning procedures that may come into play, although unlikely, especially if you disconnect the battery. In addition to the Accelerator Pedal Released Position Learning, you might have to do Throttle Valve Closed Position Learning and/or Idle Air Volume Learning. See FSM Section EC for detailed steps of these procedures.

Thanks boss! :tiphat:

Reviving an old thread of mine. Still haven't cleaned the TB's and will most likely need to complete, as my car now shuts off when starting her up and gives the same MAF code. MAF's have been cleaned earlier this year.

Just a few more questions I thought of before proceeding:

1. What are the torque specs for installing the strut bar back on?
2. Torque specs for when re-installing the TB's?
3. Just wanted to confirm to use the star patter when re-installing the TB's?
4. Would the re-learn/calibration procedures be completed immediately after putting the TB's back on without turning the vehicle on or should this be completed after driving around after cleaning the TB?

*Tried searching the forum but couldn't find this info.

Bump - anyone?

I mean....if you really want my opinion...

1. Doesn't matter, tight.
2. Doesn't matter, medium-tight.
3. Doesn't matter.
4. This I don't know, I would assume this only matters if you were physically forcing the butterfly valves to move which seems stupid at best. Just spray a healthy amount of throttle body cleaner and gently wipe everything off with a paper towel. It won't be perfectly clean but it'll get it 90-95% better, which is good enough.

I've taken these throttle bodies off maybe a dozen times at this point, don't over think it. You'd have to do something hilariously stupid to harm anything.

When installing and tightening up the strut bar. Have the tires sitting on the ground when you tighten up the nuts. If you have to car jacked up and tires off the ground. You can have a slight twist in the chassis.

1. Subjective
2. Subjective
3. Subjective
4. Though I may be overthinking this, after hours of research and youtube vids, it appears most people take the TBs off and clean both sides of the butterfly valve, which also shows them opening/closing for the cleaning. So now I feel like I've taken a step behind on whether moving the valve is safe.

Number's 1 to 3 are subjective; what might seem to be tight to you may not be tight to me, and vice versa. Need actual torque specs.

I had a random limp mode on my car that got more common mid this year. About a month ago I removed the MAFS and cleaned them, and then cleaned the TB’s with them in still. Didn’t disconnect the battery and didn’t have to relearn anything. On first start it did take a few seconds to start, but it’s been almost a month since I’ve cleaned my MAFS and TB and I haven’t had the limp mode come back.

Torque specs are in the FSM (link in my sig).

:rolleyes:

Tight is relative to the bolt. Your strength and tools are variables that you need to be able to adjust for. If you are weak and use a 3/4 inch sized socket with a 36 inch breaker bar you're likely to break off the bolt head without any effort at all.

Struts bar bolts and nuts torque to 52 Nm. This isn't some critical number. Just make sure they are tight.

Throttle body bolts torque to 8.43 Nm. Don't want to over torque these too much.

Also, #3 isn't a number. The answer is it doesn't matter the pattern. Just torque them down evenly.

I have a '13 also and seems like limp is becoming more common. Did you move the butterfly valve at all when cleaning the TBs?

Thank you sir! :tiphat:


Testing you to see if you actually read my posts lol you passed!

Yes, I moved the valves to clean. Was clean on the outside but got quite a bit inside.

Did the same 2 days ago and same as you was pretty clean on outside and much dirtier inside. Yes I moved the valves a little to. Didn't do any throttle relearn.
Left it overnight before starting and sputtered a tiny bit when started but all good after that.
I also had cleaned my MAF's about a month before this.

Just got done cleaning out the TB's. What a PITA, but what a difference in terms of feel (and def. not a placebo effect).

My car pretty much sat in the garage 6.5 days a week since I was able to walk to work, until recently, I made a career change and requires me to drive 6 days a week ironically.

The SES light would come on and the OBDII would throw a MAF sensor code, which I cleaned a few months back, but the same code kept coming on. I figured it would be the TB's based on research on this forum. As you can see from the date of this thread, this has been an ongoing issue. Most of the time, when the car starts, I could tell if it was in limp mode or not based on the revs and clutch feel, and would have to shut down for 10 seconds and restart to get out of limp mode. Recently, it got to a point where I would restart and it would stall out, unless I gave it gas, and was quite embarrassing doing this.

Process took me 2 hours. I would highly recommend having your tools in line, as I kept having to scramble looking for stuff. The biggest tool that would have helped me were the vise grips, which I couldn't find mine and those clamps were a PITA to move around and had to use regular pliers, which made taking off the intake boots extremely difficult. I read of others being able to move the butterfly valve, however, I wasn't able to move mine around (granted I really wasn't putting too much pressure due to paranoia). Having a toothbrush would have helped clean out more, as I only had rags. I sprayed the TB cleaner liberally (with a towel catching any excess flowing).

After putting everything back together, I did a few re-learn procedures, including the gas pedal reset, TB closed positions, and idle air volume, and the window reset last (I disconnected the negative post of the battery), as well as resetting all my settings the way I had it before.

Car didn't have any issues starting up. It actually started up quicker (from a cold start) and was noticeable louder, and without any hesitation like some have reported. There is definitely a noticeable quicker throttle response, even when barely tapping the gas. And the car drives faster (the car itself didn't gain more power, but rather I got back what originally came with the car). Due to not having a toothbrush handy, I don't feel as if I got all of the gunk out, but did spray the TB cleaner liberally, let it soak, and started wiping down.

Well done! I’m sure what you did will be good enough.


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I guess I have been really tired lately from the career change that I was somewhat on auto-pilot when doing this, and it occurred to me today:

1. While putting the intake boot back onto the TB, if the boot wasn't sealed all the way (for example, the flap end of the boot didn't fully go over the entire TB entry hole), I am assuming this will cause a vacuum leak and cause a code to be thrown by now?

2. I know Jarblue gave me the torque specs previously, but I don't recall using my torque wrench that uses NM (I honestly don't remember, as all I recall from the experience was my back killing me from leaning over most of the time). I'm thinking I probably over-torqued the TB allen screws. I tightened until it was firm. What are the chances of something breaking from over-torquing?

1. Probably

2. I didn't realise you actually removed the throttle bodies themselves. As long as you've tightened the allen screws "quite firmly" everything should be fine.

Yep, removed the TB's, but left the electrical and coolant lines on. When initially loosening the allen screws, they were on there pretty tight. Like to a point I thought I broke something when I broke them loose.

I cleaned my TB's while still on. It was sufficient.