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treadstone

Original Poster:

41 posts

55 months

[news] 
Monday 15th March 2010 quote quote all
Hi

After driving my 2.5 Sport (48,000 miles), very often the car struggles to re-start when the engine is warm/hot. For example after filling up at a petrol station or a trip to the shops where the car has typically been left for a few minutes up to a few hours.

When trying to start the engine again under these circumstances it seems to struggle and eventually splutter back into life after 5-10 seconds turning over. It seems to crank fine but struggles to catch. It hasn't failed to start yet, although it's a minor annoyance which I'd like to get fixed.

I've done some research and it seems the most likely culprit is either the coil packs (two of them on the 2.5) or something like a temp sensor, crank sensor, etc.

I know that the warm/hot start is a known issue on mk2's often fixed by replacing the coil pack, but I wondered if anyone here knew whether mk2.5's suffered in the same way bearing in mind the coil pack is different?

Advice and help will be appreciated!

Cheers

Sam

treadstone

Original Poster:

41 posts

55 months

[news] 
Monday 15th March 2010 quote quote all
Just remembered that a few months ago I got a CEL and the code from diagnostics was: P0012 'A' camshaft position - timing over retarded.

Would this have anything to do with the warm/hot start problem I've got?

treadstone

Original Poster:

41 posts

55 months

[news] 
Monday 22nd March 2010 quote quote all
Just going to update this thread in the off chance that it might help future readers with the same problem.

Tried cleaning and reseating the crank sensor. No joy.

Now trying to source a new camshaft position sensor and see if that solves the problem.

Will update as necessary.

Cheers

treadstone

Original Poster:

41 posts

55 months

[news] 
Sunday 28th March 2010 quote quote all
Hi

Update:

Camshaft Position Sensor obtained from MX5 Parts fixed this problem.

Cost was £48 delivered.

Took 2 minutes to change the sensors, easy potential fix for anyone who's suffering from the same symptoms.


mike9009

1,906 posts

129 months

[news] 
Monday 29th March 2010 quote quote all
Nice one Treadstone - I have been reading your posts but had nothing to add!

At least you know one person is listening to you!

Mike
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maser_spyder

6,110 posts

68 months

[news] 
Monday 29th March 2010 quote quote all
Make that two!

Thanks for keeping everybody updated, information like this is invaluable for anybody else with the same problem.

I managed to solve a leaking water seal problem on my Yanmar over the weekend because of a very similar posting on another forum, it would have been a nightmare without having somebody else's experience!


heebeegeetee

21,642 posts

134 months

[news] 
Monday 29th March 2010 quote quote all
Yeah, thanks for the info. smile

ALawson

5,037 posts

137 months

[news] 
Tuesday 30th March 2010 quote quote all
Has the Mk1 got this sensor?

Still trying to get the MX5 sorted!

treadstone

Original Poster:

41 posts

55 months

[news] 
Tuesday 30th March 2010 quote quote all
Thanks for the words of support guys. smile

I'm not entirely certain but I believe the mk1's also have the cam position sensor. Quite whether doing this for a mk1 would have the same effect I don't really know.

During my research I discovered that on the mk2.5 cars (post 2001 basically) the cam position sensor had been re-located from the font of the cam cover to the back of the cam cover (driver side)right up close to the firewall. Apparently this can cause a build up of heat that essentially fries the cam position sensor on mk2.5 cars due to its re-location further back.

My understanding is that on mk2's the same symptoms are more likely to be solved by replacing the coil pack.




NeoVR

245 posts

57 months

[news] 
Tuesday 30th March 2010 quote quote all
ALawson said:
Has the Mk1 got this sensor?

Still trying to get the MX5 sorted!
What are your symptoms?
The mk1 does have the sensor on the back of the cylinder head, on the left bank if its a 1.6 and right bank if its a 1.8

Starting problems when hot/cold are usually the engine temp sensor which is also in the back of the head.

dylan0451

1,036 posts

77 months

[news] 
Tuesday 30th March 2010 quote quote all
treadstone said:
P0012 'A' camshaft position - timing over retarded.
did you try adjusting the timing? i wonder if you could have just advanced it a bit

i'm not saying you wasted money as it all works fine now, but if you got a mechanic to fit it, he would have fitted to 10deg BTDC (i assume 2.5's are the same?) which the original could have been adjusted to, maybe?

treadstone

Original Poster:

41 posts

55 months

[news] 
Tuesday 30th March 2010 quote quote all
Don't think timing is adjustable with the VVTi on 2.5's

Edited by treadstone on Tuesday 30th March 22:24

MX-5 Lazza

7,236 posts

105 months

[news] 
Tuesday 30th March 2010 quote quote all
Hmmm... That's an interesting one. The VVT have a crank angle sensor on the crank pulley which it uses for ignition timing. This can't be adjusted without a bit of butchery.
There is a cam angle sensor that runs off the intake cam but I thought that was just used for the VVT. I guess if that is faulty it probably won't know what to do with the valve timing but I would have thought that would result in a loss of power rather than running badly.
I'm no expert in this area though so I could be very wrong.

dylan0451

1,036 posts

77 months

[news] 
Wednesday 31st March 2010 quote quote all
ahh, i forget they're variable...

i was thinking along the lines that if it's way retarded, the exh valves are opening by the point of ignition so it's not effectively making any cylinder compression

why it still starts fine when cold though? ecu puts more fuel in and vvt reduces overlap?

MX-5 Lazza

7,236 posts

105 months

[news] 
Wednesday 31st March 2010 quote quote all
Only the intake cam has VVT wink

treadstone

Original Poster:

41 posts

55 months

[news] 
Wednesday 7th April 2010 quote quote all
Right. Time for another update;

I have to make a rather disappointing and altogether embarrassing retraction on solving this particular problem.

All seemed well for a while after the new cam position sensor but sadly this week the car has been cranking for 5+ seconds without firing up more frequently than ever. And now it's doing it from cold starts, too.

This leads me to believe that the crank sensor is my next port of call. Lazza on here, and Nick at Mazda on Track kindly informed me that the timing is done from the spiked plate behind the main crank pulley. The crank sensor senses those spikes as the car cranks.

Further research however suggests that if the crank sensor is intermittently faulty and it can't sense the spikes turning round, then the car's ignition and fuel systems won't fire up, which pretty well describes what I've got at the moment.

Anyone know where I can get hold of a new crank sensor? mx5parts are all out.

Thanks








Edited by treadstone on Wednesday 7th April 15:43

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