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Discussion Starter · #1 ·
Ok, I've run out of ideas for my idling problem. I've pretty much tried everything I can think of.

She's following a very predictable pattern with her idling, and I'm hoping that someone else has seen this pattern and may have an inkling what it is. Apart from this one thing she runs absolutely perfectly.

When you take your foot off the accelerator her revs drop down to about 500RPM (she should idle at about 750). She coughs and splutters a bit, and then a few seconds later she "wakes up" again and her idle revs recover back to where they should be. When she's cold she'll stall instead of recovering. They say a picture is worth a thousand words, so here's a graph. Blue line is the RPM. At around 246 seconds she's coasting to a stop with the clutch down (no load). You can see the revs drop down (blue line) to just under 500RPM (250 seconds). Then at 252 seconds they bounce back up to where they should be, oscillate, slightly, then settle down happily to be a steady 750-800RPM. There's a clear correlation between the RPM and the MAP (orange line) but whether the MAP changes because of the RPM or the RPM changes because of the MAP I have no clue.


Here's a list of all the things I have tried (plus other things that I have done not to solve this problem):
  • Cleaned the throttle body and idle stepper motor thoroughly
  • Cleaned the MAP sensor thoroughly
  • Cleaned the injectors (injector cleaner added to fuel)
  • Replaced old fuel with new
  • New battery (because the old one died, not because of this problem)
  • New back box (old had a leak, not because of this problem, but pre-dates this problem)
There are no error codes, all sensors report everything is fine. No misfires, nothing. Just a bit of a cough.

So - any experts have any further ideas of what it might be? Anyone else seen this specific pattern of low idel revs that recover after a couple of seconds?
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