[Miata] '02 Miata Bucking Without CEL - Big Mystery!

[Bryan Wyatt]

As for when it happens, it's only when the engine is warm/hot.  This never happens cold (although sometimes it does decide it doesn't want to start cold).  It's never happened when I step on it--in fact, it always seems to happen when I am at cruise or otherwise at very low engine load and generally in the 3-4k rpm range.
 
I do not know when the fuel filter was changed last, as I purchased the car at the beginning of April.
 
I did not torque the plugs down when I checked them last (see the following thread link for what I found).  I basically tightened down with a close-wristed "grunt"--we're talking 11-17 ft. lbs, right?  I did of course check the contacts on the wires.  I actually checked the plugs almost two weeks ago and have not had any troubles whatsoever until now.  In fact, I drove all the way across Ohio without any trouble--even with the AC on; my troubles didn't start until the return trip.
 
Here is the link to the spark plug diagnosis thread - http://tinyurl.com/4c773n
 
-Bryan
 

--- On Mon, 5/26/08, Hank <Subhunter at verizon.net> wrote:

From: Hank <Subhunter at verizon.net>
Subject: Re: [Miata] '02 Miata Bucking Without CEL - Big Mystery!
To: bryanewyatt at yahoo.com
Date: Monday, May 26, 2008, 8:06 PM





Does it do it when the engine is fairly cool or only after you've been driving for a while?  Does engine load seem to come into play?  How about rpm, any particular range?  Right after fill-up or just before?  When was the last time you changed your fuel filter?  I'm sure you've already checked to make sure the plugs are torqued and the plug wires are making good solid contact both at the cylinder and the coil pack?  There are a lot of things that could be causing the problem but since it's intermittent the answers to some of the above questions might help.
 
Hank & the Scandalously Striped Silver '99
Curmudgeon Racing
Deep in the Heart of Dragon Country
Murphy, Nawth Carolina

----- Original Message ----- 
From: Bryan Wyatt 
To: Miata Power List ; Miata Mailing List 
Sent: Monday, May 26, 2008 7:41 PM
Subject: [Miata] '02 Miata Bucking Without CEL - Big Mystery!






All,
 
I'm not sure how to describe this in one word, but here goes the long version:
I was on my way home driving across Ohio this weekend and 3 separate times the car (an '02 with stock everything intake/exhaust/ignition and about 60k on the clock) began to buck uncontrollably.  The revs would bounce within a 500rpm range of whatever value they were at when the car began to buck.  The only way to "cure" the problem was to turn the car off and wait for it to cool down.  Unforutnately, the car didn't always start on the first try.  Very frustrating!
 
As I said before, the car is stock everything (I even put on a stock exhaust after I bought it).  I replaced the plugs about a month (and 1000mi) ago, but the car did this same thing on the old plugs.  It will even repeat the behavoir at random in the parking lot at work driving at no more than 25mph.
 
Any ideas?  Could heat soak be affecting the coils or wires?  Maybe even the Cam Angle Sensor?  The car seems to start up after I let the engine cool.  Is there a way I could effectively cool off the engine bay?
 
To repeat one last time...the car does not throw a CEL even after the car is restarted.
 
Thanks for your help!
 
-Bryan and The Tick




_______________________________________________
Miata mailing list
Miata at list.realbig.com
http://list.realbig.com/mailman/listinfo/miata



      
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://list.realbig.com/pipermail/miata/attachments/20080526/16321065/attachment.html