Hi all, newbie on here looking for some advice please ?
We have had 3 MX5s to date over the years, a MK1, MK2.5 and now a MK3. This is a nice 56 plate 2.0 Sport with Bose radio etc etc and hard retractable roof. Nice to drive, had it a year, but two things now bother me:-
I believe these have the Bilstein (spelling?) shock absorbers, and whilst the road handling is excellent I keep noticing how noisy they seem to be - especially when cold. I can hit a bump in the road and it’s fine, but go over a few small ruts in the road and the car clonks something awful. It sometimes feels like the suspension has had it, but on smooth roads no issues. At he last MOT they did report “misting on shock and probable degradation” but a mechanic friend to ignore it as they have to put that down if they see any misting on a shock leg. So do I have an Shock issue do you think or is there something else that causes the noises ?
The battery started going flat too often since end of Summer so I decided to change it at New Year. I did read somewhere that when you change a battery on these MX5s the car will mess around on tickover, until the ECU re-learns (??) Whatever that means. ANyway2 months later and after several short journeys and a few longer run outs, the revs still muck about on tickover. Slow down… pull up to standstill … revs drop to 500 RPM, stutter and then quickly flutter up and down six times up to 900 RPM. Last time I used the car, I stopped for petrol, and when re-starting the engine I notice the speedo needle didn’t do its usual little dance, and it wouldn’t start after three turns until finally I gave a shove on the throttle. Does this mean my ECU is on it’s way out or does it need re-mapping ?
Can’t help with the suspension query, but having recently changed the battery on my NC - and aware of the fluctuating revs issue after a previous disconnection - the following advice worked for me.
Start the car and wedge the throttle at around 2000 rpm, I used a piece of wood to push the accelerator pedal in, resting it on the front edge of the seat. Don't try and do this just by holding your foot on the accelerator as you wont be able to keep it consistent.
Leave it running like this until the revs drop to normal tickover (can take up to 20 minutes).
Remove the 'wedge' and leave it ticking over for a similar period.
Unless you have some other issue that is causing the rev fluctuation this should work after a battery disconnection.
Firstly the suspension noise could be anti-roll bar drop links worn but I would expect this to be found on the MOT. It could also be the one of the problems with the dampers discussed in the link below
On the fluctuating revs I would try resetting the ECU. Disconnect the battery and leave it disconnected for a while. Then reconnect the battery, reset the DSC and then take it for a good 1/2 hour run.
Ref battery take lead off re install making sure terminals are super tight and around the bottom of the posts
Put Key in ignition turn on but don’t start car for 1 miunte, turn off then…
Start car let Idle for 15 minutes, then switch on everything that will drain power A/C, heated seats, lights the lot and let idle for another 5 minutes then steering wheel side to side to take off the DSC go for a 5 miunte drive,should be spot on straight away.
I had the same problems as you and no matter how much I travelled it never settled down.
Mine rattles and knocks like yours but don’t know how quiet one should sound so going to wait until things fail on MOT and replace.
Thanks guys for all the feedback, and one way or another I fixed the problem, probably by fluke.
Having seen the advice I had decided to take a good look last weekend, remove battery and try the options. Then last Friday I took the car out, and having your ideas in mind I just tried a couple of things on the hoof. Whilst in traffic I sat there with my foot on the pedal and tried to hold it a 2k revs for a minute or so, and then moments later with no traffic about I drove up a slight hill in second gear, and again held it at 2k revs for about a minute. Next time I pulled up it was absolutely fine and tickover is perfect !
Not sure which of my two actions cured it but am happy now - so thanks all !
I think it’s unlikely that the suspension noise is due to the dampers - could perhaps be caused by play in the drop links? Re. the misting, I’ve had the same advisory on two of my MOTs; at the last service & MOT - April 2018 - I mentioned this to the garage (both rear dampers) & authorised them to replace them if they thought it necessary. When I picked the car up the mechanic said that the issue was very slight & nothing to worry about, the dampers would be “good for years yet”. As replacement Bilsteins are listed at £245 each for my car (MX-5parts) I took this advice!
Incidentally I’ve seen a few threads with regard to the fluctuating revs issue after replacing the battery - pleased to hear that it was sorted. I swapped my battery last year with no issues at all (aside from the usual reprogramming of the stability control, radio etc) - revs were fine from the start of the first trip after I did the swap. Seems to affect some cars & not others I guess?