Almost Completely FED UP... help?

[Luciano]

I\'ve almost had it with my FD now.

I had a problem with my FD a while back as detailed in  this thread.

And the problem didn\'t really go away.   It is, however, slightly different now.

This is the problem:
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The car runs absolutely fine when cold.  

As soon as it warms up (water temperature reaches "quarter to" position), the strange behaviour starts.  

I thought it was "limp home mode", but I don\'t think it is anymore, as the engine management light doesn\'t come on, and no fault codes are stored.

The "strange behaviour" is that if you apply more than just a little throttle, the power cuts completely out and it backfires.  

You can ride the clutch (to get the revs up without applying heavy throttle) and get the car to accelerate up to 40/50mph+, but as soon as you put your foot harder on the accelerator, the power cuts out and it backfires.

If you pull over, turn the ignition off, and then start the car again, the car will drive fine once more - for about 200 metres, when it will go into the strange behaviour again.

If you stop and let the car cool down to 0 again, it will drive fine for a while, until the engine heats up again to normal operating temperature and the problem starts again.

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So there you go - that\'s the problem.  My Dad is a mechanic but hasn\'t worked on FD\'s before, so we\'re struggling to determine whats causing it.  I would take it to a specialist, but I don\'t really have the money, and I don\'t want to spend lots of money getting a specialist to fix it, when my Dad could do the labour if we knew what the problem was.

If anyone has heard of this before and knows what it could be, please let me know!

Thanks in advance
Luciano

[MikeLMR]

I would have a look at the engine coolant sensors, there should be two, one for the ECU and one for the gauge. My 323 drove terribly when the ECU coolant sensor plug came loose because it would try and run in cold start mode when hot.

[Carl]

is the MAP sensor connected?
Regards
Carl

[Luciano]

Map sensor is connected

[Carl]

Are all of the earths well grounded and clean on the contact points?Do you have a stock ECU?
Regards
Carl

[Luciano]

I think the ECU is stock (I haven\'t changed it, and it looks stock to me)

I will check the earths - any in particular I should look out for?  If an earth wasn\'t grounded well, wouldn\'t it mean that the problem would occur even if the car was cold?

Thanks,
Luciano

[framey]

MikeLMR, would you please expand on this? I didn\'t know there were two. Any chance of a diagram to point out the locations please?
Thanks
(I may have a similar problem)

[JayDee]

I think it could be your coolant sensors aswell, they are on the back of the theromstat housing, one has a green plug and one underneath is black, I think this is the one, but check both.
Does the power cut when the turbo starts coming on, if it does it could be the charge control solenoid.


Jason

[MikeLMR]

on other Mazda\'s the green one is the ECU temp sensor

the black one is either for the gauge or may be the sensor for the fan.

[kbareham]

What you are describing is almost identical to mine, except mine is more intermittent. When the fault is there, it stays there until you do anything to clear it. Then it works for several weeks or more before it fails again.
I haven\'t got to the cause of mine yet, but this is what I have discovered. There is a actuator known as the charge control valve. It\'s function seems to be to hold a valve closed on the outlet of the second turbo when the second turbo is not in use. When mine runs properly, I can measure about 600mm hg continous vacuum at this actuator, which seems to hold the valve closed properly.
When the fault occurs, the vacuum drops to around 400mm hg at idle, and this drops off as you open the throttle. As it drops to about 200mm hg, the car cuts out. I\'m guessing that 200mm hg is not enough to hold the valve closed, and so the output of the first turbo is free to flow into the outlet of the second turbo, which has the wastagate open and the charge relief valve open venting back to the air filter. I don\'t know why it causes the apparent cut out, and there is no ECU light, but Im sure that reverse flow down the second turbo is not a good thing!
You might want to measure the vacuum to the charge control valve, and if it is low or not there, trace back toward the solonoids to try to find where it has gone.
I have no idea why the car runs fine when its cold either. I\'m guessing that it might be associated with the activation of the double throuttle valve, but haven\'t worked out why!

Rgds
Keith

[Luciano]

That definately sounds like my exact problem!!  It used to be more random with my car too, but now I\'m making regular identical journeys, I can identify more of a pattern.

Someone must know why the Vacuum drops like this...?

I\'m going to replace the engine coolant temp sensors, and also the turbo actuators, and see if that solves the problem.

Also, is the turbo actuator the same as the turbo solenoid and the same as the charge relief valve?  If not, what is the difference, and which do you recommend I replace?

Thanks!

[nikp]

Just out of interest, how do you know if ECU codes are stored? And how do you read them?

[eatmyrx7dust]

Is nobody local with Apexi and Commander.
The Commander provides diagnostic readings for all sensors and its very easy to swap stock ecu for apexi (5 mins max.)

[eatmyrx7dust]

I will oblige if your in the northwest area !!

[Luciano]

Thanks for the offer.  I\'m in the North East, but have no way of getting the car to you unfortunately!