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Erratic idle at non-erratic intervals


Zod

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Hi Guys,

 

Having a weird issue with my HR. When idling at normal temperature at about 700-ish rpm, the revs drop (as if it's going to cut out!), then it revs over 1000 and settles back to 700. The weird part is that this happens nearly bang on every 28 seconds without fail. I've performed the idle reset + ecu reset etc with no joy. I've listened out / looked for vacuum leaks and I'm thinking of cleaning the MAF next.

 

Any ideas what would cause this? :wacko:

 

Keith

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I had the intake off several weeks ago replacing the plugs but the problem manifested more recently.

I also pulled a multiple cylinder misfire code last week that hasn't come back but thought this may be just down to my timing pulling off from the lights coinciding with the dip in idle..

 

It's the 28 second interval that has me stumped.. There is clearly a logic behind it.

 

Really hope it's not an ecu issue!

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I was worried about mine as it was idling at 1100-1200, spoke to Jez at HDev about it and he filled me in about it not being an uncommon fault on the HR . An idle relearn solved my issue though

 

The only thing I can think is air leak or poss lambda fault but think this would trigger a fault code

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I have a code reader permanently connected via carpc but there are no other codes. I suppose I could try disconnecting both Mafs to see what happens. If the problem persists then it would suggest the issue lies elsewhere. Don't want to go cleaning something in case I damage it unnecessarily.

 

Are the Mafs even in play at idle?

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  • 4 months later...

I know it's been a while but I thought I would update this thread and put closure on the problem. I eventually tracked this issue down to a breather hose I had left disconnected when I changed the plugs. Car idles and drives perfect again! :)

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