Miata Mailing List: December 1996, Message #63
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   From: (none)

Subject: Attack of the Killer Shell Gas (an update)

   Date: (none)



Hi all...



Well, Enzo is still having indigestion with gas. (har har har) I tried Shell

gasoline again, and the knock came right back. In fact, I've also experienced

the knock with Chevron gas, too. The knock seems to be audible only at the

very very low rev range, and only when the car is under load. No knock is

audible at idle, and on the freeway the knock isn't there either. When

accelerating (hard or soft) the knock can't be heard unless I pick too high

of a gear (which bogs down the engine). The strange thing is that Texaco and

Unocal 76 gas seem to be OK, although Unocal 76 is debatable (I've been using

89 octane and last night thought I heard a slight knock, but I might have

just been tired).



Am I the ONLY person on the list who is having a problem with knocking & gas?

Even if there *is* something weird about Shell (and now Chevron) gas, if Enzo

is the only Miata out there which is having a problem then there is

(obviously) something wrong. I can't keep trying different gas brands, hoping

one will prevent the knock. That's just treating the symptom, not the

problem.



History: About 11 months ago, a Mazda dealer improperly replaced the oil plug

and caused a small drip. 3 days later, the plug popped out while I was

driving fast on the freeway and I lost all my oil. I shut the engine down

while my oil pressure gauge still showed some pressure (probably 10 - 15 psi?

(is psi the right term?) -- the needle was below the "30" setting but not at

zero), but the pressure was dropping fast. Enzo seemed to start up & run fine

once a new plug was installed & oil was added. Might this little episode have

anything to do with my current problem? Also, I did run the car for about a

month with my timing at 18 degrees, but put it back to 10 for compliance with

SCCA Stock Class rules and because Enzo had lost his oomph for freeway

driving. Currently, my timing is set to 14 degrees (and it feels right --

freeway driving still has punch and the low end is just a bit better than

normal but not as powerful as it was when set to 18...so I don't think I made

a mistake and set my timing way to high or way to low).



Any suggestions would be appreciated. I think I will take Enzo to a dealer

once finals week is over, assuming this problem continues. I'm now less than

4,000 miles from an expired warranty, so now's the time if I'm going to have

Mazda look at the engine....



Happy Motoring!     -ZACK



|\  Kerim Zackariah Broadbent         #176 CS

| \  RacerZack@aol.com                 Cal Club &

|  \  red '94 Miata, "Enzo, Jr."        San Diego

|___\  PLAY CAR in Fullerton, CA         SDMC/SOCALM

 1904   ============================      Team Voodoo

         24 Units until I graduate from Cal Poly!!!!!!