MAF sensor troubles

Spooks4 · Postby **Spooks4** » Sat Dec 05, 2020 9:16 am

Gday All

I recently been having some issues with my SE and an odd idle issue with terrible fuel mileage.

My thoughts pointed towards the maf sensor

I had it not want to start on me the other day until I finally held the accelerator enough to hold its idle, limped it home and haven’t drove it since.

I did get a scanner to it and got a P0103 code which says the maf output voltage was too haha high.

I’ve since replaced the maf yesterday and took it for a drive and it now seems worse then before.

The codes not there but the car is jumps around at idle and nearly stalls out at low rpm even with the clutch in.

Is there something more I needed to do when replacing the maf or do you think I have another issue ?

Thanks in advance for any help

greenMachine · Postby **greenMachine** » Sat Dec 05, 2020 10:44 am

Check the wiring, especially at the connector, there may be broken/frayed wires. Find another MAF, plug it in and see if it makes a difference. I have one, where are you? (I assume this is a stock setup?)

Otherwise check all the hose connections and the hoses themselves for vacuum leaks.

:mrgreen:

Spooks4 · Postby **Spooks4** » Sat Dec 05, 2020 10:47 am

I’m in Newcastle nsw, I have access to an NB maf in the girlfriends car, already tried it and no difference, think it might be the wiring or a vacuum leak

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Nevyn72 · Postby **Nevyn72** » Sat Dec 05, 2020 12:12 pm

Speaking as an SE owner, check your intake pipework between the turbo and throttle.

Mine has done exactly the same thing twice now, in both cases the BOV hose popped off the intake elbow.
A big leak anywhere along the intake pipe after the turbo would have the same effect......

Spooks4 · Postby **Spooks4** » Sat Dec 05, 2020 12:14 pm

Nevyn72 wrote:Speaking as an SE owner, check your intake pipework between the turbo and throttle.

Mine has done exactly the same thing twice now, in both cases the BOV hose popped off the intake elbow.
A big leak anywhere along the intake pipe after the turbo would have the same effect......

I’ll double check that tonight thank you

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Spooks4 · Postby **Spooks4** » Wed Dec 09, 2020 6:45 pm

Checked all my intake hoses this weekend and replaced one that I thought was the culprit but nothing has changed, I sprayed all the pipes with throttle body cleaner while it ran to see if I could find the a Leak that way but also found nothing.
Any other suggestions ?

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manga_blue · Postby **manga_blue** » Thu Dec 10, 2020 7:46 am

SEs have OBD2, don't they?

I'd start by putting an OBD scanner on it and checking live data for MAF, ECT, IAT, O2, TPS

Spooks4 · Postby **Spooks4** » Thu Dec 10, 2020 8:03 am

manga_blue wrote:SEs have OBD2, don't they?

I'd start by putting an OBD scanner on it and checking live data for MAF, ECT, IAT, O2, TPS

Did that last night, should have taken a photo of the stats and posted them here but I forgot to. Going to leave it to a mechanic friend of mine this weekend and hopefully he can sort it. He’s an MPS specialist but has worked on my SE and a few other mx5s over the years.

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StillIC · Postby **StillIC** » Thu Dec 10, 2020 8:20 pm

This sounds like a problem I had with my naturally aspirated Celica, and one a friend of mine recently had with his Mazda BT50 turbo diesel. Symptoms are more or less the same in all three cases.

The problem on the Celica turned out to be the concertinaed tube between the air flow meter and the throttle body. It took me a while to find it, however. I removed the tube and it looked fine. I flexed it a bit and it looked fine. But when I was putting it back on I had it at a funny angle and guess what, it opened up some big cracks at the valleys of the concertinas on the underside of the tube. When the engine flexed the tube under acceleration it opened up the cracks (which were otherwise not visible even when looking at the tube directly). This happened as one end of the tube was attached to the chassis via the AFM, the other end to the engine via the TB, and the engine really moves a lot on standard engine mounts.

Friend's BT50 was a similar issue: hot side of an intake tube (on the boosted side I think) that opened up when the engine was under load and moving relatively to the chassis in the engine bay. The fact that it needs more air when doing this exacerbates the issue.

So, have a real good look at your intake tubes and flex them significantly to visually open up any cracks that may be present.

Spooks4 · Postby **Spooks4** » Thu Dec 10, 2020 8:27 pm

StillIC wrote:This sounds like a problem I had with my naturally aspirated Celica, and one a friend of mine recently had with his Mazda BT50 turbo diesel. Symptoms are more or less the same in all three cases.

The problem on the Celica turned out to be the concertinaed tube between the air flow meter and the throttle body. It took me a while to find it, however. I removed the tube and it looked fine. I flexed it a bit and it looked fine. But when I was putting it back on I had it at a funny angle and guess what, it opened up some big cracks at the valleys of the concertinas on the underside of the tube. When the engine flexed the tube under acceleration it opened up the cracks (which were otherwise not visible even when looking at the tube directly). This happened as one end of the tube was attached to the chassis via the AFM, the other end to the engine via the TB, and the engine really moves a lot on standard engine mounts.

Friend's BT50 was a similar issue: hot side of an intake tube (on the boosted side I think) that opened up when the engine was under load and moving relatively to the chassis in the engine bay. The fact that it needs more air when doing this exacerbates the issue.

So, have a real good look at your intake tubes and flex them significantly to visually open up any cracks that may be present.

Will double check all of them man, thanks heaps for the tip

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bruce · Postby **bruce** » Fri Dec 11, 2020 1:59 pm

Have the engine running when flexing the tubes to hear any change in engine note.

Spooks4 · Postby **Spooks4** » Fri Dec 11, 2020 2:02 pm

bruce wrote:Have the engine running when flexing the tubes to hear any change in engine note.

Will do, have a funny feeling it could just be rubber cuppling that connects the maf and it intake pipe itself might not be sealing properly

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bruce · Postby **bruce** » Fri Dec 11, 2020 2:25 pm

Wrap a ton of electrical tape around the connection to see if that fixes it?

Spooks4 · Postby **Spooks4** » Fri Dec 11, 2020 2:26 pm

bruce wrote:Wrap a ton of electrical tape around the connection to see if that fixes it?

Will give it a crack and report back, this is why I love this forum, so many things I over look or don’t think about

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manga_blue · Postby **manga_blue** » Fri Dec 11, 2020 10:40 pm

Spooks4 wrote:
manga_blue wrote:SEs have OBD2, don't they?

I'd start by putting an OBD scanner on it and checking live data for MAF, ECT, IAT, O2, TPS

Did that last night, should have taken a photo of the stats and posted them here but I forgot to. Going to leave it to a mechanic friend of mine this weekend and hopefully he can sort it. He’s an MPS specialist but has worked on my SE and a few other mx5s over the years.

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It's not actually the stats that you need to analyse. My experience with failing MAfs on euro makes is that there's a period of time where they keep flipping between working and not working, with the cause being either the MAF wearing out or a wiring fault in the plug or loom. You can't rely on fault codes to pick them. You have to watch the live display of the flow over a few minutes, preferably while someone else drives the car, looking for blips.

Having said that the only bad MX5 MAF that i've seen was an NB8B one that consistently gave rubbish under-readings.