Miata Mailing List: November 1993, Message #116
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   From: moore@email.ncsc.navy.mil (Jim Moore)
Subject: Re: Idle speed drop
   Date: Wed, 10 Nov 1993 08:21:55 -0500

MANSON@fsd.com says:
     
    speed droops to roughly 200-300 rpm (based on crude tach readings), and the
    car shudders slightly as if it is about to stall.  The speed recovers then
    - I have much faith that it will not stall - and everything is fine again
    after about 2 seconds.]
     
I didn't mention my experience in the previous thread, but let me pass it
along now.

On a trip to Atlanta last month, I was cruising I-285 around 75mph (just 
keeping up with traffic, I swear!) and everything was absolutely fine.
When I reached my destination (Stone Mountain), as soon as the engine came
back to idle it started running VERY roughly; if I kicked the accelerator
pedal hard, the engine would either backfire and die or stumble badly and
then climb out of the dead zone; it would rev to redline fine once it got
past the bad place. My odometer had 36,500 at the time, so methought "aha!
tis the dreaded and widely reported spark plug wire failure," whereupon I
coerced yon brother-in-law to hie me down to the nearest Pep Boys to pop for
the lifetime wire set. After installation the engine seemed to run fine at
idle, so I thought I'd fixed the problem. Only problem was, once I got back
out on 285 to attend a developer's conference, by the time the engine was
once again fully warm, the poor thing started dying again (and I don't think
it was related to being on I-285, though that is a Very Bad Place for a 
tiny car with a stumbling engine). Finally took it to the dealer (with said
brother-in-law right behind me in case it died again), who (1) replaced the
spark plug wire set again, and (2) cleaned the throttle body, which, he said,
was heavily laden with carbon deposits. The service manager told me that the
spark plug wires are covered under a separate, 5yr/50,000 warranty and    
charged me only for setting the engine back to specs ($48). I also took the
opportunity to get my backup light switch replaced.

The problem did not occur gradually, as I would expect with any kind of
buildup; it was sudden and debilitating. Ran fine all the way home, and
since. Hope this helps. Sorry it's long.

-- 
Jim (moore@email.ncsc.navy.mil)

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