My Miata - fix up & hopefully better mileage!

[Stubby79]

Say hello to my little friend!





Hopefully she's not shy, or I'll never hear the end of it...temperamental? Perhaps! Wants attention? I've never met one that doesn't!

No, I didn't just buy her. I've had her probably 5 years or more. 2 years ago, she was running a bit rough, noticeably at night...I assumed she didn't like the cold and was showing her age. She's got a bit over 300k kms on her. Thought it pretty safe to assume the original engine in her was getting tired. Right? Made sense to me at the time. So when I bought my Firefly, I parked her when the insurance ran out. Put some fuel stabilizer in her, and that was that.

The real nail(s) in the coffin came when the battery croaked and the master cylinder leaked out, leaving her with no brakes. Despite interest a year or so back in having her going again, I wasn't interested in working on something that would only run like a turd, even after the $$ and hours thrown at it. No thanks. She was worth too much on paper to just throw away, though. I kept meaning to get her ready to sell and let someone else deal with. Never got there, though.

I wanted to tinker on a car this past weekend, so I grabbed my spare battery for my Firefly, stuffed it in the Miata, and for a lark, went to see if she would start. She fired right up!!

Well, $#!^. If she's going to play that nice, I guess I should give her some attention.

She still idled rough, just as I remembered. My head had 2 years to forget most of my theories as to why, so I was able to on her with "fresh" eyes. I started with the basics. I pulled the spark plugs to tell me a tale of how she is running internally. Plenty of carbon, so she has been running rich and/or not getting decent combustion. Might as well check that plug gap while I'm there. Oh. Dang. It's waaaay out. Closer look shows the electrode is decently worn. Easy to notice with the V-groove. It was more of a v-groove. No wonder it isn't running well.

All 4 spark plugs were the same. All 4 got adjusted. Stuffed them back in and...she practically purred compared to before. D'oh! My bad. I put so few miles on my cars and always put fresh plugs and such in them when I buy them...I've never worn spark plugs appreciably in any other vehicle in the past 15+ years. It never really occurred to me that this car would wear them down in 15k. Apparently it will, though!

Going over the brakes shows she eats through those in a hurry too. Hungry beast! Explains why I was always scrubbing brake dust off the front wheels.

Anyway, I put insurance on her that morning and have been driving her all of two days. She's loud and unruly, but I am thoroughly enjoying it after all these years of driving a lethargic Firefly and more recently a heavy Jetta TDI. I've gone from frowning every time I look at her to smiling again. Fun little cars. You should get one!

[Fingie]

Nice color

[Stubby79]

After the brakes, it was time to tackle cleaning the engine grounds. There are 4 of them that I am aware of:

Main ground strap:


Easily accessible, near the brake booster. Looks like I need to deal with the surface rust from where brake fluid ate the paint.

Multi-ground point:


Hiding directly under the brake booster. Complete pain to get at. Not convinced it's for the engine.

One beside the FPR:


And one below:


The first one also bolts to the head.

The second one I relocated, because it's dang hard to get at.

The third and forth both bolt to brackets which are in turn bolted to the head, so to ensure a clear path for the electricity you need to clean the brackets too. The wiring harness is in the way, and just happens to turn a fairly easy job in to a pain.

All connections were cleaned and coated with protectant, so they should be good for years to come.

And holy heck, what a difference! Smooth idle, restored power at low rpm, and no more hesitation/struggle when the alternator gets heavily loaded at slow idle. I can now cruise in town in 5th gear!

Why is it always something simple? And something you keep putting off?

[Stubby79]

What's next? Well, I've addressed all the pressing issues. It's time for something more frivolous!

LEDs!

I started simple with the interior lights. No dome light on these things, just footwell lights. As soon as I started mucking around with it, it stopped working altogether.

Pulled it out and found the + connection solder joint had come off, even though nothing I had done up to that point would have put any strain on it. Also discovered someone had butchered one of the wires and when he crimped it back together, he tangled it in the main wiring harness, so even unplugged, you couldn't pull it out. Had to pull said wire apart to do it.

Before:


After:


And finally with an over-sized bulb pressed in:


Said bulb is pinned in place between the tabs and the light's plastic body, and isn't going anywhere. It's 39mm instead of 31mm. Why? Because it was the brightest that I had on hand. You have to have access it from the back as well as the front to get it in there like that, or it will end up slipping out through the hole in the back.

And, for comparison's sake, LED vs incandescent:


Great for seeing your feet in the dark!

And this morning it was on to exterior lights. Not that I have the bulbs that I need, but there's something to be done first...modify the flasher unit.

You need to swap out this little 5.6kΩ resistor, R1:


For a 1MΩ resistor. Thus:


And viola! Your flasher unit no longer cares if there's too little or too much resistance/current going through the bulbs. It will just flash at it's steady rate, whatever bulb is or isn't in.

And, hey, it works! Even if I only had 2 bulbs on hand to put in at the moment.

[MetroMPG]

Originally Posted by Stubby79

Say hello to my little friend!

Hello, and subscribed!

Coincidentally, I just started tinkering on the MPGiata a couple of days ago (Cuba-franken-style radiator replacement -- ie. cobbled together with parts from unrelated cars ).

She fired right up!!

Nice! Mine did too, surprisingly quickly. And with much less valvetrain clatter than the last time it was woken up, after a 1+ year slumber. It was only 4 months this time.

I've gone from frowning every time I look at her to smiling again. Fun little cars. You should get one!

Yup, they are definitely smile-inducing. I just want a nerd gear, for when I'm up to speed. Silly high RPM.

Question: do you think cleaning the grounds helped, or was it mostly spark plugs?

[Stubby79]

Originally Posted by MetroMPG

Hello, and subscribed!
Question: do you think cleaning the grounds helped, or was it mostly spark plugs?

I'm going to say they were both about equally important. She was driveable again after adjusting the plugs, back to about what she was always like for me before. She always felt a bit like she was carburated...you know, gutless...until you get the rpms up a bit. I always blamed the aftermarket header, assuming it was hindering things at low rpm.

I was wrong, as I discovered on my drive to work yesterday. And, more noticeably, on the drive home, in the cool wee hours of the morning. Which I assumed was the problem...not the fact that I would have the electrical system loaded up at night, even though you could feel an added vibration when stopped at a light with everything turned on and the indicator blinking. The vibration came every time the indicator would blink on. I was aware of this and meant to clean those darned grounds, but never did, because the next day I'd go for a drive - no lights on - and she would be fine and dandy.

Anyway. They're both important. And I'm an idiot for not cleaning those ground connections years ago. Anyone with an older car should go clean theirs ASAP. If you want a happy, healthy engine, anyway.

I'm looking forward to getting through the old gas and seeing what kind of gas mileage she'll get now.

[Stubby79]

OTOH, perhaps if I cleaned the ground connections first, the spark plug gap wouldn't have been such an issue. It would have presumably been easier to jump the enlarged gap if it had better power. Still too large of a gap, though!

[MetroMPG]

Do you have any play in your wiper linkages? (I imagine they might have gotten more of a workout through the years on the wet coast than here.)

Mine was very sloppy, and I just looked into it this evening: the nylon bushing that connects the link arm to the motor was completely disintegrated. (To the point the previous owner had wrapped it in duct tape to keep it from popping off!)

[Baltothewolf]

Another Miata pops up, cool.

Mine isn't for MPG (Dispite me driving it easy right now because the Insight is down). I have larger tires (205/65r15?) and I'm hard pressed to get 30mpg, but I can take a hairpin at 30 and hook up good :P.

[Stubby79]

No, I haven't noticed any play in my wipers. I'll double check by hand, but they run smooth and park properly, so I've had no reason to check them.

Hopefully you can buy jsut the bushings. If not from mazda, there are generic "Help!" ones out there that might fit.