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Erratic idle

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Erratic idle

Postby Pops » Sun, 09 Apr 2017 1:15 +0000

Possible fix for erratic idle after disconnecting battery.
I had the erratic idle problem after disconnecting the battery, tried all suggestions to fix but nothing seemed to work, but as time went by the problem seemed to be getting better (but very slowly )but still a right nuisance in traffic with the revs fluctuating from about 400 to about 1200 on idle.
The reason for disconnecting the battery....:I had been trying various things to cure what I felt was a lack of power and heavy on fuel ,including new fuel pump,temp sensor etc, (after doing the timing belt the power has returned) it was suggested that I disconnect the battery and press the brake pedal to reset the ecu. It was after this that the idle problem erupted , I tried all suggestions to no avail , so started backtracking what I had done in the past. Somehow I decided to start by refitting the old fuel pump, when I released the pipe from pump TO engine there was massive pressure in it,( no noticeable pressure in the return pipe),so much that it sprayed fuel about 10feet behind the car . So without disconnecting the battery I refitted the pump, started the car and have had no problem since , I believe the cure was releasing the fuel pressure and letting it reset itself . Might be worth trying for anyone who has the same issue.
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Re: Erratic idle

Postby Real Rayzor » Sun, 09 Apr 2017 5:00 +0000

That's very interesting Pops... as you know I've the same problem and have tried everything as well. Where did you release the pipe.. At the engine side or at the pump.
2002 MK2.5 Sunlight Silver (sold)

1992 MK1 V-Spec. Brilliant Black, Fully Restored
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Re: Erratic idle

Postby Pops » Sun, 09 Apr 2017 5:28 +0000

Real Rayzor wrote:That's very interesting Pops... as you know I've the same problem and have tried everything as well. Where did you release the pipe.. At the engine side or at the pump.


Ya, at the pump ( was changing it anyway),pressure was high enough to spray fuel about 10feet behind the car.
I really don't know if it's a cure or not but I haven't had the problem since so it has to be worth trying.
John
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Re: Erratic idle

Postby TOM 5252 » Sun, 09 Apr 2017 8:09 +0000

Hi Guys
There are instructions in the Haynes manual for releasing this fuel pressure. It is slightly different for different years of MX-5,but essentially says to start the engine and then remove the fuel pump relay and wait for the engine to stall. Then switch off the ignition. So you don't have to open any pipe joint to release the fuel pressure to try a reset.
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Re: Erratic idle

Postby Real Rayzor » Mon, 10 Apr 2017 12:53 +0000

Thanks Tom.. will give that a go.. TBH... I was was having visions of petrol flying all over the place. Lol
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Re: Erratic idle

Postby Steve » Mon, 10 Apr 2017 7:32 +0000

fuse is 2nd from front in the engine bay fusebox (30A).
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Re: Erratic idle

Postby Pops » Fri, 14 Apr 2017 3:31 +0000

Did you try it yet Ray ? I've had no problems with the idle ever since without doing anything else.
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