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Discussion Starter · #1 ·
Hey guys!

I have a mk1 mx5 with a 1.8 VVT engine running a td04 turbo...

Ive been struggling lately with my AFR's being really rich, showing between 10 and 11 on a cold start on my gauge. Then 12 when warm.

Keep fouling plugs and car wont even start atm.

When warm AFR's seem ok (above 14) if I hold at 2k revs.

Im about to give up and take it to a tuner If I cant figure it this out.

Ive taken some logs on my ME221 of cold and warm start as well as a short drive if anyone can check to see if something looks off?

ME221 logs - https://mega.nz/folder/44gQ2AzL#JYTY_ogk0hEHdd_yzdzOHQ

Cheers :)
 

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Find Alex Hickson in the ME and turbo/supercharged groups on facebook if you think its a tuning issue, was it running okay before the turbo?
 

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Discussion Starter · #3 ·
Yeah had the turbo on for a while. Was running great last year. Recently changed my manifold to a kraken but that shouldn't make this big of a difference?

Also managed to get it running again earlier, went for a drive and at low revs under load it will hesitate. Feels like the car dies for a split second, with revs dipping down to 0 then back up.

I'll ask on that page too, thanks man!
 

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Try cleaning up your throttle body and your ICV if you can! Could maybe be the crank angle sensor cause that can cause issues as well
 

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Banish a little rust a day people
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Pretty sure AFRs of 14 are dangerously high on a turbo car.

Gasket sealing ok? No other changes to the build since? What's the warm up enrichment in the ECU set like?
 

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Discussion Starter · #6 ·
I've had a look at the crank angle sensor today. Turned ignition on and rotated the crank and heard the sensor pickup the 4 teeth. But it might be going bad, just intermittent, so still looking to replace.

AFR's of 14 are ok when idle and cruise aren't they? Its still mostly around 12's and under boost its in the 10s.

its definitely running rich rather than lean, I wouldn't dare drive it at all of it was lean.
It was mapped by Bofi and been on drift days with the previous owner.

I did have an exhaust leak as an MOT advisory. Not entirely sure where. The reason I swapped over to a kraken was because my old mani kept cracking. So that had a massive leak and didn't run this bad.
Only changes I've done are new exhaust manifold, downpipe extended 3" and new plugs.

Maybe old fuel isn't helping?

Heres a pic of my warmup

qzOL3m7.jpg


From what Yugen said I did some research and the symptoms very much sound like the crank angle sensor (hard to start, revs drop to 0 randomly) So will keep looking into that

Cheers!
 

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Banish a little rust a day people
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Ok yeh that's fine, I thought you meant during accelerating it was going to 14s at part of the map. Enrichment looks ok.

I had the same symptoms with regard to revs dropping/bucking, hard to start, hard to keep going at low rpm and running rich and it was a crank sensor. I'd replace it sooner rather than later or it'll destroy the cat (if you have one) and will just fail to start one day. I got a used one from autolink and so far no issues 3 years later.
 

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Discussion Starter · #9 ·
Do I even have a crank sensor? Or am I being dumb? haha.
I thought it was that thing with the dashes on it but looking online thats not the case. Looked both sides and nothing, no wiring leading there either

S5saWQC.jpg


30SsnNr.jpg
 

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Banish a little rust a day people
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You might not, I think some of the early cars didnt have one? Might be the cas sensor on it's way out then
 

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Discussion Starter · #12 ·
Looks like the Cam sensor isnt even plugged in and has no wiring lol
8FU4079.jpg


Coil packs are a good shout! Guess Id just have to buy some new ones and see if it makes any difference
It would be super helpful if my ME221 actually threw out diagnostic codes lol
 

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Happily expanding the To Do list since 1997
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At the top of that photo of the VVT engine's cam sensor you can see the engine has been fitted with a Mk.1-style cam angle sensor.

The Mk.1 CAS supplies two signal outputs (one to give crank* timing and the other to give engine phase) equivalent to both the crank and cam signals on the Mk.2s and it's output can be understood by a Mk.1 ECU. So I assume your car was originally running the Mk.2 engine on its original Mk.1 ECU so it needs the CAS fitted in the spot where the Mk.2 engine originally just had a blanking plate.
 

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Discussion Starter · #15 ·
At the top of that photo of the VVT engine's cam sensor you can see the engine has been fitted with a Mk.1-style cam angle sensor.

The Mk.1 CAS supplies two signal outputs (one to give crank* timing and the other to give engine phase) equivalent to both the crank and cam signals on the Mk.2s and it's output can be understood by a Mk.1 ECU. So I assume your car was originally running the Mk.2 engine on its original Mk.1 ECU so it needs the CAS fitted in the spot where the Mk.2 engine originally just had a blanking plate.
Yeah its a mk1 running the VVT engine but using an ME221 ecu. Was running sweet last year but now trying to start after winter and having trouble. I'm starting to think it may be something simple like the fuel filter and old fuel.
 

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Discussion Starter · #16 ·
This is what happens when you buy someone else's project hehe, lots of learning to do. So yeah what Martin Y said is correct I'm using the Mk1 CAS and its wired as is outlined on the ME website https://motorsport-electronics.co.uk/mazda-mx-5-vvt-swap/

So Ive changed the fuel filter yesterday, old one looked ok with clear fuel coming out of it but its cheap so why not. And I'll put some fresh vpower in.
When I was doing the fuel filter I noticed the PPF ground strap was snapped and read this can cause all sorts of issues so looking to fix that too.
Also pulled the plugs and they're fouled again which is why its not currently starting, so ill wire brush them.

And ive been looking at my map, started taking some fuel out of the warmup table. Still was getting and AFR error of between 1 and 2 in MEITE. But hopefully that'll stop my plugs getting fouled so quickly.
Saw a couple guys also having this issue in the ME facebook group. Car is tuned and running sweet but slowly the car runs more and more rich, sounds like an ECU bug or something lol
 

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Happily expanding the To Do list since 1997
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Sounds like you're getting on top of it now. Good to hear. I'd get that ground cable fixed as a priority.

A bad ground can create all sorts of oddities because sensors produce output signals as voltages relative to whatever they're grounded to but the ECU reads those voltages relative to its own ground. So if different parts of the car have different or constantly changing ground voltages you just don't know if the readings are real or nonsense.
 

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Discussion Starter · #18 ·
Hey guys,

Been a while and thought I'd give you an update. So, tried taking the car to a tuner but it broke down on the way haha. Luckily he's a nice chap and picked me up with his trailer.

When trying to start the car again it was getting no sync. So we switched the CAS to one he had from another working car. Didn't fix it, so we had a look at the wiring and it's quite a mess. As the car is a mk1 and it's a vvt engine. Looks like the previous owner has used plug connectors on the COPs and they aren't shielded at all so tuner thinks the CAS is getting interference.

Plan is to get a vvt loom instead of using this hacked up loom and use a crank sensor instead of the CAS like they are originally on these engines.

So hoping its just bad wiring which would make sense. Car would struggle to start and when driving car would die for a sec but come back if I was in gear with enough revs. Felt like I was bump starting it lol. And got worse and worse until it just died and wouldn't start again :( it's in good hands though. Kind of happy it happened as I was close to buying a new CAS and that wouldn't of fixed it.
 
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