Maintaining a used MX5 NB3B (2003)

[slipshot]

Hi all

This is intended to be a post that I continue to add to - for anyone who has purchased a used MX5 NB and would like to know what key things they are doing or could do and how to do it. Much has been discussed on here already so this is just reinforcing people's thoughts and ensuring that they can do it if they want. Where I can I'll do most of the work myself.

I've owned two MX5's in the past in England. One was a 1993 white one, 1.6L, the latter was bought brand new in 1997, British racing green, in the base 1.8 spec which had no power steering (which I wanted but have now realised and appreciate that the car was actually designed to have power steering and tends to handle slightly better). After one year of ownership and while under warranty I got bored with the lack of power, so imported a Jackson Racing supercharger kit, fitted it (as well as an active knock sensor) to the car and had way more fun. It was the only the second supercharged MX5 in the UK at this time.

As for this car - it has 149,000km on it, and documented service history until 70,000km. But it runs well, handles nicely but needs some work doing to it. It already has a new condesnor fitted and four new (but pants brand Goodride tyres) fitted. So this is meant to be my approach to what I do and how I do it. I'm fortunate in that this is a toy/hobby car as I also have a Passat R36 for the school run. Things to be done (some of which already have):

Clean the drain holes
Clean the roof properly
Replace the side indicators with clear ones
Replace the orange quarter lights with clear ones
Repair the heated rear window
Replace the standard stereo with my Alpine head unit, Boston Acoustics speakers with crossovers, and locate the amp under or behind the rear seat, and install a mic for bluetooth
Replace the interior light with an LED bulb
Perform a foamectomy on the drivers seat (I'm 6'1")
Remove the aftermarket cruise control
Find and replace (or see if it will work) the indicator and wiper units to a UK spec one which has the indicators on the left (I know this is not in the spirit but I actually want to see if it can be done and the hassles with it)
Have a full service and full check done including replacing the cam belt, waterpump, oil and oil filter, coolant, brake fluid, diff oil, gearbox oil, air filter, fuel filter, spark plugs
Clean the throttle body
Perform an upper engine clean using Subaru upper engine cleaner
Replace all exterior bulbs with either LED's (including indicators as I have an LED flasher unit)
Replace the rear exhaust with either a single or double exit system
Look at installing a cold air intake (depending on the exhaust noise)
Replace the two rubber bushes under the centre console for the gearbox - both of which are quite perished
Repair the black snap fastener on the tonneau cover - one of which, behind the passengers seat, has broken
Investigate the bunny hopping at approx 1500 rpm when off throttle and brake

And now added - replace the throttle body as I have noticed, by chance, that the stamping on the current throttle body says BP-4W which relates to the 1999 - 2001 engine whereas I have the 2003 BP-Z3 engine. Hmmmmmmm

[slipshot]

Cleaning the drain tubes

As with many cars, drain tubes have rarely been looked at all cleaned. This one was no exception. Looking form the top both sides had a small puddle of water in them. Further investigation revealed they one was fully blocked and nothing would drain while the other had a small drip drip from under neath. Any amount of heavy rain would have easily overflowed this area.

First was to use a suitable implement to clean these from top down. I ended up using some electrical cable which had enough flex in to bend but enough to be forceful too. Using a funnel and water I just get tapping away at the blockage from the top slowly dislodging items - drivers side first. Every now and then the flex would move a bit more but there was no such easing of the water or pressure and then the flex would hit something hard and stop. This was about 3/4 down the drain tube at a rough guess.

The passenger side was totally blocked but this, using the same methods, was easier to unblock - lots of prodding and then a little whoosh and the dirt started dripping out harder. I then poured more water while 'plunging' the side and it all slowly seeped out and washed away. At this stage water would run through but not perfectly so there was still some blockage.

Moving round to under the car, I then stuck my finger up into the tube to see what i could feel. Not that I have a particularly long finger but there was a blockage (or the star flap) but whatever I did suddenly there was a full on whoosh and all the crud of years shot out. This is my hand immediately after the waste shot out...

So this was clean. Did the same to the other side but no suck luck so with more plunging from the top and lots of poured water, it slowly loosened everything and eventually it ran clean.

Now I have both drain holes lovely and clean from top to bottom...

[smy0003]

So you got one!
My silver nb8b had also found a new home.
Good to see you on here

Sent from my GT-I9505 using Tapatalk

[slipshot]

Yes I did... took a while but this was a fun project. Glad you sold yours in the end.

[hks_kansei]

re: the drains.

I just use a roll of the black sprinkler piping, it's rigid enough to push past the gunk, and being a hose I can direct water/compressed air down it to help loosen stuff.

I just shove it in until it comes out under the car, then just sort of "floss" it back and forth to clean it.

[TrackAttack]

And now added - replace the throttle body as I have noticed, by chance, that the stamping on the current throttle body says BP-4W which relates to the 1999 - 2001 engine whereas I have the 2003 BP-Z3 engine. Hmmmmmmm

I think you'll find it is the correct throttle body. There will be many things with BP4W part numbers on them. That doesn't mean it comes from that model. There will be parts on your car that use B61P part numbers as well. Whatever Mazda can carry over to reduce costs they will.

[slipshot]

And now added - replace the throttle body as I have noticed, by chance, that the stamping on the current throttle body says BP-4W which relates to the 1999 - 2001 engine whereas I have the 2003 BP-Z3 engine. Hmmmmmmm

I think you'll find it is the correct throttle body. There will be many things with BP4W part numbers on them. That doesn't mean it comes from that model. There will be parts on your car that use B61P part numbers as well. Whatever Mazda can carry over to reduce costs they will.

Thanks - very good to know. Have a feeling the throttle body is not that great though anyway so given you can get aftermarket replacements for about $300 from the US, may well invest in those for the fun of swapping it over and seeing what happens. I made the assumption, yes, so could well have got that rather wrong.

Anyone else out there with a 2003 MY that can check and see if their TB has any marking or nomenclature on it that would help me work this out?

[speed]

Always good to see new things in the garage section

Don't think a larger TB on a stock manifold will do much power wise.
Madjak has had success with a performance Honda manifold however he does have other mods ;)

[de Bounce]

I had a NB8B with the VVT motor which developed an issue with the Idle Air Controller (it's attached to the throttle body)
Despite my best attempts at clean the IAC I couldn't get it to work correctly.
I swapped in the complete Throttle Body / IAC from an earlier NB8A motor.
Later I swapped my NB8B throttle body, less dodgy IAC into a NB8A.

From my limited experience all the NB throttle bodies are interchangeable and probably the same.

If the throttle body isn't causing any problems, leave it alone.

[slipshot]

Thanks you chaps - most helpful.

Something is going weird anyway. The car has this little thing of, when nice and warm, if you come off the throttle and brake (and clutch) so are in effect coasting in all gears but mainly in 2nd and 3rd, at about 1,500 rpm is starts to bunny hop - a gently jerking as if it's a fuelling issue or a throttle body or IAC issue. Anyhow, it's currently in with the mechanic to do everything and has now had:

New timing belt and water pump (he was impressed i supplied the woodruff key!)
New oil and oil filter
new air filter
new fuel filter
new diff oil
new gearbox oil
new spark plugs (the leads were pretty new anyway)

I've now ordered and received a stash of press studs and will try and replace the broken one that caused the wind to get underneath and flap around. I'm lucky it's on the end of rear shelf and not in the middle as it's far easier to get access to the part underneath. This image shows it as the very left one.

I also had the flappy drinks holder issue which was easy to fix following the instructions on numerous sites - now working fine.

Oh and I'm also going to replace the cigarette lighter which is worn and does not always work (i have a replacement) and also wire in both the centre cons lights bought from MX5Parts UK and wire in another 12v socket (bought from Aliexpress) under the dash for the tomtom...

and a good check all over of which not much needs to be done for now other than a new set of pads on the front. So we shall see how it drives and if the problem has been solved...

[hks_kansei]

Thanks you chaps - most helpful.

Something is going weird anyway. The car has this little thing of, when nice and warm, if you come off the throttle and brake (and clutch) so are in effect coasting in all gears but mainly in 2nd and 3rd, at about 1,500 rpm is starts to bunny hop - a gently jerking as if it's a fuelling issue or a throttle body or IAC issue. Anyhow, it's currently in with the mechanic to do everything and has now had:

The issue sounds to me not like a fault so much as just a minor driving habit.

Generally in a fuel injected manual car the ECU will try and do it's best to keep the engine idling at a certain speed, if you brake in gear and the revs drop enough sometimes the ECU thinks it's going to stall and tries to increase the revs to keep it at the nomral idle speed.
If you're in gear it can feel like an odd chugging.

I find mine will do it, but can't remember the RPM, but I think it's around 1200 or so.

I'd say just try and not brake in gear at such low revs, either clutch in or use the next gear down.

[slipshot]

Thanks for your comment, but I have to say having dríven/owned many manual cars, including two MX5's, this is not normal. Perhaps I did not explain it well, but let's say you are at 2,500 rpm and on a flat road and the light ahead changes to red. You are in gear since there is no need to dip the clutch, and you are not braking as the car will slow down by itself. SO you are off all pedals. The car will slowly drop revs until about 1,500rpm (or even higher) when it will then bunny hop. Nothing wrong with the car and certainly not straining it at all. What's basically happening is that in a normal manual I'd dip the clutch about 1,000 rpm. In this car, I have to dip it about 1,800 rpm to stop the bunny hopping. That's not normal - nor did any other MX-5 I test drove do it. So hope this clarifies the point...

[hks_kansei]

ahh, my mistake.
I thought you were trying to brake with it in gear down to below 1500rpm.


I'd still suspect something with the idle system, maybe hook up a tach and check it's idling at the correct speed (850rpm give or take 50 from memory)

[slipshot]

ahh, my mistake.
I thought you were trying to brake with it in gear down to below 1500rpm.


I'd still suspect something with the idle system, maybe hook up a tach and check it's idling at the correct speed (850rpm give or take 50 from memory)

Agree - she idles fine though and very rock steady when warm, less so when cold but that i can understand. Something is playing up but will see how the full service works and go on from there. Just one of those things that's bugging me... ;-)

[joshuam]

Ooohh, I love the colour

I think more pics are in order when this round of work is done