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Had some maf issues a while back with some weird idles and low power, have since replaced maf, pulled off my AEM intake back to the turbo and checked all hoses.

Also cleaned out the throttle body and checked the rubber elbow and stock bov.

Mechanic took the car for a drive with a scanner and found “nothing wrong” the car seems to idle okay but there is definitely still hesitation on acceleration which I’m guessing is a vacuum leak.

I know there’s some little weird issues with SE’S from time to time so anyone who has owned an SE I need some wisdom.


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Vacuum leaks "usually" present as a high or erratic idle.
Is it just hesitation (jerkiness) on initial throttle input and then runs fine over 3000rpm or right through the whole rev range?
When I had leads fail it got to the point where I could barely get the car moving but then when up to 40kph etc it was fine.

Roadrunner wrote:Vacuum leaks "usually" present as a high or erratic idle

Seems to start off erratic but settles down at about 900rpm, seems to drive okay but feels like it’s out of time or something.

Roadrunner wrote:Vacuum leaks "usually" present as a high or erratic idle.
Is it just hesitation (jerkiness) on initial throttle input and then runs fine over 3000rpm or right through the whole rev range?
When I had leads fail it got to the point where I could barely get the car moving but then when up to 40kph etc it was fine.

It’s not jerky but it definitely feels like something is holding it back, I was thinking maybe just spark plugs. It still pulls through the revs okay but doesn’t feel like it used to


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Giving this an update as I’m still chasing issues on my SE.

Found out my timing belt jumped a tooth so it was running retarded. Now the car seems a lot better however not perfect.
I noticed my MAP sensor or the boost sensor?? On the drivers side is making a clicking noise when I pull the throttle cable.

The car is running good but not awesome, seems to be a little sluggish down low but picks up once it’s in boost.

On a cold start I can here a low popping spluttering noise coming from the exhaust as it drops in revs.

Gonna change fuel filter and spark plugs very soon to see if that helps at all.

Thanks in advance for any advice fellas.


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Remote diagnosis is always difficult, and doubly so given the SE's known idiosyncrasies. I am going to say that I have no idea what is wrong with your car, but given the infamous bog issues, I'd be looking at the bog valve and cleaning it, something that should be on every owners 'to do' list if their car is running the stock ecu.

My best option would be to take it to someone who knows MX5s, and preferably has worked on SEs and knows them. I can't make a suggestion as to who, as you don't say where you are in your profile.

Failing that, it will be a hit-or-miss process of working your way through the possibilities.

Good luck!

I'm wondering how a timing belt jumps a cog?

greenMachine wrote:Remote diagnosis is always difficult, and doubly so given the SE's known idiosyncrasies. I am going to say that I have no idea what is wrong with your car, but given the infamous bog issues, I'd be looking at the bog valve and cleaning it, something that should be on every owners 'to do' list if their car is running the stock ecu.

My best option would be to take it to someone who knows MX5s, and preferably has worked on SEs and knows them. I can't make a suggestion as to who, as you don't say where you are in your profile.

Failing that, it will be a hit-or-miss process of working your way through the possibilities.

Good luck!

Fair points there, I’ll start at the valve and work my way around. Thanks for the advice anyways, I think it’s just going to come down to forking out for someone to run more diagnostics in the end. :/


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bruce wrote:I'm wondering how a timing belt jumps a cog?

Spoke to the mechanic who did my 100k service about it and he said it’s possible he could have installed it wrong.

Not sure how I wouldn’t notice it being out of time but for whatever reason I didn’t and it was in fact out.

Has definitely fixed the original sluggishness but the car still doesn’t seem right. I’d say running out of time for a time has for sure messed with a few components so I’ll be replacing them in the hopes I can figure it out.


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I had similar issues and what I did that fixed it for me

- replaced CPS, crankshaft position sensor
- changed new spark plugs
- reassembled and refitted my nitrodann CAI
- cleaned my MAF sensor

Car runs fine again and I think it was a slight vacuum leak with the air intake that was the culprit. That or the CPS.

My only issue is now sometimes on cold start idle will bounce around for a bit and sometimes even stall until it warms up... Never ends

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luzinit wrote:I had similar issues and what I did that fixed it for me

- replaced CPS, crankshaft position sensor
- changed new spark plugs
- reassembled and refitted my nitrodann CAI
- cleaned my MAF sensor

Car runs fine again and I think it was a slight vacuum leak with the air intake that was the culprit. That or the CPS.

My only issue is now sometimes on cold start idle will bounce around for a bit and sometimes even stall until it warms up... Never ends

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Thanks for the all the info mate, I’ll be replacing stuff in the coming weeks and see how it goes.


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