Miata Mailing List: October 1997, Message #175
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From: 	Jim Creer <ojcreer@groupz.net>

Subject: Help-Engine Stumble

Date: 	Wed, 1 Oct 1997 15:38:47 +0000



Looking for help



Problem:  Getting symptoms of misfire while hitting bumps in road.  Problem

is not constant, and may or may not occur from small pavement imperfections

to bigger jars at RR Crossings.  In some instances noticed quick flash of

engine light, burp in fuel pressure gauge, and slight headlight dimming.

Problem noticed at cruise, full boost, or partial throttle.  Not noticed

during deacceleration, but may not be noticeable.  Miata is dropped 1 inch

and has very stiff suspension.  Cannot simulate problem at home.  Cold or

hot engine is not factor.



Actions:  First went to ignition wires. Crimped some ends a little tighter,

so all connections were very snug.  Even swapped wires out with another new

set.  Checked all electrical connections, to include hard wiring of MSD.

Pulled all unneeded fuses for quick test drive.  Symptoms persist.

Throttle cable is tight.  Clamped the throttle to 2.5 K RPM, bounced my 190

lbs of groceries in the seat and on fender areas.  Rocked the roll bar as

hard as I could.  Pulled, poked. and shook everything, to include dead blow

on everyhing reachable.  Even did load test.  Pulled rear bulkhead to

examine Fuel Pump and area.  Little things fixed : loose common chassis

connection in trunk, partially seated pins in diagnostic connector,

slightly loose vacuum connection, missing screw on cooling fan mount,

broken screw on water pump pulley, destroyed O rings from air box to turbo,

destroyed K&N air filter (had to scrape with razor blade of air box.]

Uncorrected:  weak motor mounts.  Will get to these shortly.  The latter am

sure contributes to the symptom, but dont think is cure for the problem.



Got two weeks to play before the next track event.  Would sincerely

appreciate comments from readers that may have had similar problems and

direction on what to check next.  Hope is simple cure that has been

overlooked.  Keep thinking about the Car Tech FPR, but dosen't seem logical.



Thanks in advance



Jim Creer 

ojcreer@groupz.net