Possible MAF wirring issue?

Hey guys,

I'm thinking I may have the same issues as described in this thread:

https://legacygt.com/forums/showthread.php/engine-running-rich-af-learning-d-12-15-p5396993.html#post5396993

I've done several searches so far and the wire harness issue seems to come up often?

My issue:

Throttle response is odd/laggy and getting a lot of knock feedback showing on my AP, often -8 and higher (especially between gear shifts). Not sure what would be considered "normal"? I was told by my mechanic that having a forged block, the sensor might be picking up on the "piston slap" type noise. Also the tuner apparently lowered the sensitivity and suggested I change the sensor as it has nearly 200,000km on it (they get too sensitive after a certain period of time apparently)....does any of this make sense?

Funny coincidence.....I have the Grimmspeed CAI installed (without the box for the moment) and EBCS. Yesterday I decided to quickly check while the car was idling the EBCS for any lose hoses and it seemed fine. I then looked at my CAI which claps/hoses also seemed fine. I then noticed a corner of the air filter was a little damaged as it is leaning on the engine bay/inner fender area. When I touched it for a better look I immediately noticed a change in the idle. I continued moving/wiggling the CAI and then the MAF wiring and kept noticing a change in the idle....at 1 point it almost stalled.

So at this point I think its fair to say there's any issue and would like to do some further testing but would need some advice on what I need to do (I'm no expert/mechanic by any means)? If this is a known issue what's the recommended "fix"....do I need to completely change the wire harness?

As previously mentioned, I have a COBB AP (V3) and would also like to know what I should be monitoring/logging to further understand what's going on?

I have a good/general understanding about cars but want to learn more about the technical things such as: the learning values, fuel trims, knocking, etc....what's considered Good/Bad, what to look out for, etc....can anyone share a link or any documentation in order to help me better understand the values I'm seeing with the AP? It's a great tool but not knowing how to use/read it seems counter-productive if I'm unable to pick up on issues which can lead to engine failure....I just dropped-in a freshly rebuild / forged engine 2 months ago and would hate myself for ever if something catastrophic were to happen to it due to my own negligence / ignorance

Let me know if you guys need any further info/details.

Thanks gang!!

Sounds like your aftermarket air filter is damaged and leaking erratically. A stock airbox would be a great start, unless you're running over 350WHP. Please start by posting a full list of mods.

So you think because my air filter is slightly damaged, that is what's causing the issue?

Here's the grocery list (engine only), everything was done 2 months ago:

- Rebuild EJ257 block with forged pistons/rods

- Fully refreshed heads

- JDM TGV Delete

- Stock injectors (cleaned, new rings and flow tested)

- DW65 fuel pump and new fuel filter

- VF52 with OE wastegate and new inlet

- AVO I/C (1st version I believe) with stock BPV

- 3" catless UP/DP with custom catback (3"mid + 2.5" Y )

- Grimmspeed 3 port EBCS

- Grimmspeed CAI with box (box not currently installed)

- COBB AP (V3) with custom Protune map

* My end goad is to get in the 350-400hp range (reason for the CAI), next year I hope to upgrade injectors and turbo to get there if all goes well.

Thanks,

Given your goals, I retract the suggestion of the stock air box. Obviously it sounds like the problem is there or close to it, so the next steps are simply careful inspection and testing of everything in that neighborhood.

Is the filter firmly clamped/sealed to the hose? Does the filter have a little tear or other defect?

Attach your ohmmeter to both ends of each MAF sensor wire and wiggle. Any major fluctuations in resistance?

If all that is perfect, maybe a problem with the sensor itself?

Given your goals, I retract the suggestion of the stock air box. Obviously it sounds like the problem is there or close to it, so the next steps are simply careful inspection and testing of everything in that neighborhood.

Is the filter firmly clamped/sealed to the hose? Does the filter have a little tear or other defect?

Attach your ohmmeter to both ends of each MAF sensor wire and wiggle. Any major fluctuations in resistance?

If all that is perfect, maybe a problem with the sensor itself?

Thanks,

With a quick visual the air filter seems ok in terms of rips/defects but has a slight dent in it from leaning into the area I described....all hoses/clamps appear well fastened.

I'll be taking everything off this weekend for a closer inspection and testing as you suggested.

I also found a post in NASIOC which suggested having the MAF replaced every 100K miles or more often if you run an oiled air filter. Prior to installing the CAI, I had a stock air box with a high flow Perrin filter and noticed I may have over oiled it the last time I cleaned it....so perhaps the MAF got contaminated and is now faulty? Seeing its never been changed, chances are I'll buy a new one just for peace of mind, including a new Knock sensor which the tuner had also recommended.

Is all this making sense and can explain the knock feedback I'm seeing on my AP and/or the gas peddle feeling I'm getting (ECU pulling timing) ?

I'll also be going through all the hoses to check for any leaks as that seems to also great similar issues based on other posts I've come across.

Any help/info you can provide regarding the data logging and further understanding all this stuff?

Much obliged,

Here's the service manual if you don't have it,

http://people.csail.mit.edu/ilh/vacation/

I clean my MAF at lest once a year with a short spray of MAF cleaner from the auto parts store.

I have been running a oiled air filter since about 3000 miles. still running the MAF that came in the car.

Here's the service manual if you don't have it,

http://people.csail.mit.edu/ilh/vacation/

 

I clean my MAF at lest once a year with a short spray of MAF cleaner from the auto parts store.

I have been running a oiled air filter since about 3000 miles. still running the MAF that came in the car.

Thanks Max !!

Ok so I took off the air filter and definitely a rip in it...grrrrr.

Could this alone be causing the issues I'm experiencing?

What should I be monitoring with my AP to know for sure?

Thanks,

I believe you need to adjust the tune for a cone style. Not sure if that will effect your MAF by just being a cone.

You might reach out to "covertrussian" for help.

I believe you need to adjust the tune for a cone style. Not sure if that will effect your MAF by just being a cone.

 

You might reach out to "covertrussian" for help.

As per the initial posts, OP is heavily modded and tuned accordingly.

Oh yea, thanks for reminding me.

Yea, pretty good with these cars, and was one of the members I was thinking about telling the OP to PM for help.

But now that your here, do you have any ideas for him ?