Help with Erratic Idle Problem, Possible Dead MAF Sensor

Hey guys, I need some advice on whether or not I'm looking at a dead MAF sensor. I've been having erratic idle and stalling problems for the last 2 months and today I have tried to record my problem via Conzult to show what my sensor's are reading to help give me a clue as to what's wrong with my Z.

In the last few days my Z has been stalling constantly when at low revs. It also has a hard time starting in the morning's when the engine is cold. I took this initial video of the cars start up routine so you can see what I'm talking about.



Now with Conzult, I needed to press on the accelerator to stop the car from stalling a few times.



My currently thinking is I either have a fuel starvation problem or an air starvation problem. I did some digging on the net last night and I found a video of another 300zx owner who was having almost the same problem I am having and he solved it by replacing his MAF.

So today my first point of call is to check whether my MAF sensor is dirty and if so, clean it with some contact cleaner.

After removing the nose panel, I disconnected the MAF harness connector and it looked like this;



The MAF connector looked like so;



So far the connector's look good, no corrosion that I can see and no need for cleaning.

So I took the air filter box out completely and then removed the MAF sensor and checked it.





I'm pretty sure the sensor looks perfectly fine and doesn't appear to be dirty in any way.

I gave the unit a wipe down but I didn't want to spray the sensor as it didn't look like it needed it.





Before I put the air filter box back onto the car I first needed to clean the inside of the air filter box as it appears more of the air filter oil has gather in the lower sections of the air box.



I thoroughly wiped the area down making sure there was not a speck of oil left and I'm considering going back to the OEM dry paper type of air filter now considering the amount of oil that is leaking from these K&N filters.



I reinstalled the air filter box back on the car and I decided I would try and see if the Z starts without the MAF sensor connected. To my amazement it did and guess what it was holding a stable idle and my 02 sensors were reading 9.0 volts for a change.



I then tested what would happen if I suddenly connected the MAF sensor in while the car was running. This is what happened



I again tested the car with the MAF sensor disconnected but I used ECUtalk this time and from what I can see the car is in limp mode and wont rev above 1600 rpm in park.



I took the Z for a short drive around my block and the car wont rev above 2500 rpm, but it was driving alot more smoothly and there was no shuttering or drops in idle when coasting.

So what I want to know is, from the information I've shown does it appear my MAF is dead??

Any help would be much appreciated​

 

Ecu has detected an afm signal fault.....

If the ecu detects afm voltage outside a set of given parameters, it will substitute the TPS signal and limit rpm to 2400. This does not mean your afm is at fault, it could be a harness or terminal fault that is affecting the voltage to the ecu.

To test your afm, check voltage on the 2nd terminal. It should read approx 0.8V with ignition on (not running) and 0.8-1.5V @ warm idle.

 

Thanks for the advice zx299, from what I can see in my videos my AMF volt readings is around about 1.10-1.30 volts which I think is normal.

I have posted my issue on the US and UK forums and one member on the uk forums said it looks like a bad MAF sensor but I want to get another MAF and test it in the car just to be sure.

Ill do a conzult and confirm the volts before starting the car and after just so that's been covered.

Please if anyone else can have a look at my videos and can provide any other information on what looks like could be the problem please let me know.

cheers

 

Middle terminal on plug look suss. Clean them all with contact cleaner. I believe if you disconnect the maf sensor and it runs o.k it is an easy way of telling the fault is sensor related ? or corrosion on that circuit. On your video you have no voltage on the air flow meter ? ( just noticed you have it disconnected )
Cheers
Dave

 

Really, It does look out of place thatls for sure, I was told on the UK forums that I could have a dry solder joint on the board on the MAF as well.

 

Find someone close to swap a known good AFM

I had a bloke stuff around trying to work out what was working and what was not for ages.
Took it to Niall who swapped out sensors till he found the culprit.
In my case it was the AFM.
put in aftermarket newie and fixed some of the issue but the idle sounded like yours. It seems the aftermarket ones work OK if your running at operating speeds but mine kept stalling and wouldn't sense the right mix at idle.
changed IACV , in case this had mysteriously chucked it in (too much of a coincidence) and nothing changed
bought a new OEM AFM and all's fixed.
the bottom line is its $300.00 bucks so PITA if it ain't the cause ..
that's why best to try a swap with a known working one .. then if it fixes it then bite the bullet and buy a newie or good second hand one.
The wreckers I spoke to wanted $330.00 plus delivery and I could get a new genuine one online for $290.00 delivered - I think they need to get a grip on reality instead of their donger..
Beware the second hand market
happy hunting

 

Thanks for the advice coolum, I have been thinking the exact same thing and have already enquired with a local member wrecking a Z if I can purchase a according to the ad a working MAF sensor for $50 and hopefully use it as a test sensor before I buy a brand new one.

also can you tell me where you can find a brand new OEM MAF sensor for $290 delivered?

 

Check the IAC/AAC connector also.

Looking at your Conzult/Ecutalk readings I notice the IAC/AAC reading moving. If I understand how they work that reading should be steady and as the engine temp increases the output should decrease slowly.

While the car is running disconnect the IAC connector and reconnect it or disconnect and check for corrosion in the connector.

MichaelZ

 

The story with the IACV is I replaced it with a brand new aftermarket model when I did a plenum pull in November last year, Thinking that could be the problem I have since removed it and put my old original IACV in. Currently the IACV idle adjustment screw is maxed out and and when I was trying to adjust the idle, i couldn't get the idle to go above 750 rpm. In my diagnostic videos I noticed the when my car was at operating temps and the IACV went below 40% the car would start to splatter and shudder violating. I noticed the IACV % would decrease up to 60% to smooth out the idle before repeating the process once it got below 40% again.

According to the UK forums this is what I was quoted by a member who stated he had a similar problem as I am having and suggested I replace the MAF

 

Whether it is the MAF or not is the question but:

http://www.ebay.com.au/itm/New-300z...ssories&fits=Plat_Gen:Z32&hash=item1c32d98eca

These are not o.e.m. but they do the job just as well

I bought one of these (for dual maf setup) and tested it and the values came back perfectly, I substituted the original o.e.m. maf for this and ran it in single mode just to make sure and it ran fine as expected.

I don't know what others think about these chinese copies, but as far as I am concerned - they work properly and do the job and you can save a couple of hundred over the oem.

Worth considering anyway.

JC

 

Thanks for the link JC I have looked at ebay and am considering my options atm. I would prefer OEM just to be safe but money is tight for me these days so its good to have cheaper options available to me on this. thanks again

 

I decided to try and see if spraying the MAF sensor with some electronic component cleaner could fix my MAF but unfortunately there was no change to the cars poor start up and it still could not hold idle and stalled. I am hopeful I can get a working second hand MAF by next week which i hope will fix my problem.

 

What about the connectors?

Understood. I am wondering if the connector was inspected and is there a difference with the IAC connected and disconnected?

MichaelZ

 

From memory when i was trying to diagnose this idle problem at the start when disconnecting the iacv nothing changed and though i have replacement connrctors for the iacv & fmci i cant solder them in while my thumb is recovering.

 

I to agree the air flow meater is stuffed, i may be rong but try the fuel regulator too, that was my problem.

 

Thanks gimpie, my fuel regualtor is brand newish only a year old. I still think its air related as it runs fine without the maf connected. I plan to buy a brand new maf on monday if the second hand seller doesnt respond to my pms.

Again i really appreciate all the advice everyone has given me regarding my problem. Hopefully it will be all fixed in a couple of weeks.

 

HI Mate sorry for the delay in getting back to you with the new AFM .. this is definitely the good model .. my aftermarket one worked OK on the hwy but not at idle so keep off that road unless you have money to burn.
The ebay link for JECS BOSCH newie
is
http://www.ebay.com.au/itm/NEW-Genu...a-/121114912822?ssPageName=ADME:X:RTQ:AU:1123

if you call Brendan below
msg=
Please contact me on (I can PM his mobile if you want it or contact as a message through ebay) to organise.
Cheers,
Brendan
(PEC)

He'll do one delivered directly for $290.00 less than wrecker crap.
Just tell him to give you a good deal as hes saving EBAY and paypal and give him your Visa No direct.

but first make sure your car is fixed with a swapped AFM is my advice if you can
ALSO
remember to adjust your idle IACV if you've been stuffing around after installation....
what a bugger of a place to put the idle adjustment eh?
Steve

 

Thanks for the links steve atm im still waiting for a second aff from a local member who is abit slow pming me back. I definately want to swap out my old afm as soon as i can get my hands on a spare afm but i just have to be patient atm.

 

Just a little update for you guys. After waiting for a week to get the second hand afm tested the seller has told me it isn't in 100% working as as he first thought. So I have decided to bite the bullet and I have purchased a brand new afm from z1 Motorsports who had it on special. I should hopefully get it in a week or so and I prey this new afm will fix my problem.

Again I appreciate all of the support and advice everyone has given me regarding my issue. I appreciate the links and offers for aftermarket and second hand afm units. I will post my results when I have them.

 

Good luck with the new AFM, Adam ... you are certainly going through the wringer.