View Full Version : check engine light

02-18-2002, 08:07 PM
Note: this doesn't really apply to older Brit cars, but it *does* to most of our newer daily drivers.....
Sunday morning I'm driving the Oriental Elan out to get coffee and the Times. "Check engine" dash light flips on for no apparent reason. I pull over, wondering if Mazda has included a "Lucas effect" to make the car seem more Lotus-like. Oil, coolant, belts, etc. all OK. Keep going (I really *need* that coffee). At the store it occurs to me to check the gas cap.......sure enough, it's loose.....the Miata has been obediently warning me that it has a "fuel vent code". I tighten the cap.
[side note: here in NJ we are not *allowed* to put gas in our own cars.....most of the gas guys are courteous and efficient immigrants......but my last gas fill was done by an all-American slacker-dude-doofus......figures!]
Light is *still* on when I get home. We go shopping.....still on. We go to a family party 70 miles away. It's still on. Daughter #1 shows up at the party and tells me the same thing happened to her new Subie. Called the dealer and they told her to check the gas cap. She tightned the cap and the light went out in 2 minutes. My sister hears the story and recounts how she was charged $75 to "reset the computer" after her gas cap is left loose (I know this is bogus dealer gouging.......her Malibu will reset after about 5 "clean" restarts......found this out when I took a course in GM diagnostics a few years ago)
But I'm not sure about the Miata (and there's nothing clear about it on MiataNet). My two E.E. brothers tell me to clear codes by disconnecting the battery. I'm pretty sure that'll work, but it's a pain to get to the battery....and besides, it's *cold* out.
I drive home. Light's still on. I drive to work. Light is still on. I figure I'll disconnect the battery when I get home. As I pull up my street, the check engine light finally goes out. Figures.
Note to all: if the check engine light goes on in your modern car, examine the gas cap......if it's loose, it make take up to 200 miles of driving to clear the computer codes.....also: don't let any "slacker-dudes" near your gas cap. images/icons/smile.gif

02-20-2002, 11:43 PM
what year is your Miata? Mine's a '96, and I had tons of check engine light triggers last winter, every time the outside temps dipped below twenty-ish degrees F. In fact, I joined MiataNet because of that-I was searching for info about the EGR system (which my dealership told me was the problem), and stumbled on that site. What;s your "handle" over there? (mine's the same)
As for the light itself, like I said, they seem to trigger for no good reason. The dealership charged me mucho bucks to have the EGR solenoid and tubing replaced because of "ice in the lines" (vacuum lines, I later learnt from a shop manual, and not from them). The light came on in their parking lot, they cleared the code, and it came on again next day. In all, my car spent about a month at the dealership having random parts (it seemed) replaced. It went out as soon as the temps got above twenty or so. If yours is staying on, you may have to bite the bullet and get the shop to clear it, even if it was just the gas cap. Engine management computers often times hold the codes, even if nothing's wrong. With OBD II (which any car after 94 has), disconnecting the battery will not do it, or so I'm told.
Good luck, I know how infuriating that can be!

02-20-2002, 11:46 PM
PS- really, you can't put your own gas in the car? Just the opposite around here-I haven't seen a full service gas station, where someone comes out and puts the gas in for you, since our local Union 76 station (Kuchera's in Geneva) closed its gas pumps and went over to strictly servicing cars, Something to do with having to replace the tanks and not being able to afford it.

02-21-2002, 12:58 AM
I'm not actually on MiataNet (so no "handle")....I just looked up their tech info area and couldn't find all that much on "time required to clear codes". One of my friends owns the URL to "roadsterchat.net" (another big Miata site), but he wasn't sure and neither were some of the other guys I knew over there. Forget my local dealer....he'd charge me for "diagnosic time" while playing a guessing game.
If you're having regular code triggers, you might want to do the simple (paper clip) diagnostic. Stick a paper clip (or thin jumper wire) in the diagnoatic connector between GROUND and PIN #10.
It'll flash codes depending on what's wrong (may want to try it on a sub 20 F day, to see if the EGR (or whatever) is acting up. Info for this procedure is at:
As far as I can tell (I'm guessing, but it's based on a fair amount of recent reading), disconnecting the + side of the battery and then grounding it will clear codes even in OBD-II cars (of course, if the problem isn't fixed, it'll re-trigger the light right away). I'm also pretty sure that many cars will clear codes after a certain number of "clean" (no code) restarts (there is some business of "hard" codes and "soft" codes....not sure about that). The Miata light's been staying off so I think I'm OK.
BTW my car's a 2000 base model I bought new (as a leftover)last March.
Yes, we are not allowed to pump our own gas, even if we want to (oddly, we also have some of the cheapest gas in the nation.....$0.96/gal for regular down the street from me). The Spridget is a bigger pain with regard to "no self-fueling"....even though it's a street car, it has a fuel cell (for local track events), and has the filler cap inside the trunk. Always seems like it takes 5 minutes of explaining "why, what and where" before I get my 8 gallons of gas.

02-22-2002, 05:11 PM
.96/gal? Sheesh! I just filled up the Mazda at a buck-six a gallon, and I had to get out to do it myself! (Granted, I prefer it that way. With the exception of Mr. Kuchera and his employees, I've never met a full service gas pump jockey I trust around my car). As for the paper clip trick, I've been told that it won't work on my '96, but I am a bit shy about sticking metal objects into car computers anyway. The possibility of screwing it up and having to replace it all outweighs the cost of having the shop scan it. I'm not concerned about it, becuase, other than at start up when all the warning lights trigger as a bulb check, my check engine light has stayed out since last February. However, I have been driving it more than I did then (slightly longer commute to work warms the engine up just that little bit more).
Good luck!