Q&A Technical issues solved
Michael Cleverley of Cleverley Repaired Cars, expert on all things MX-5, answers your questions
Electrical woes abound, and a reader wants a cheap power upgrade solution for his mk3
QI have a mk3 coupe with the folding metal roof. It all works OK, but recently the rear deck has started to judder badly when closing. I have tried oiling it, but it’s no better: any suggestions?
AThis is a problem we’ve seen a couple of times now and it’s been quite easy to cure. You need to work out which side of the rear panel is juddering by getting an assistant to open and close it while you have a look.
Next, undo the two 10mm headed nuts holding the metal deck panel to the motor unit. Note the height shim positions and using a marker pen draw around the mounting point so you can refit the panel in the same position. I usually undo only one side and support the panel with a rolled up towel or similar, but you could remove it completely for better access.
Now you can remove the motor and gear assembly; it looks a bit like an electric window lifter. It’s held in place by two 12mm-headed nuts and a plastic trim is clipped to it. Push the trim to one side and then lift out the unit, disconnecting the two multiplugs as you do so.
On the bench you’ll see that the motor is bolted to the gear frame with three screws: these come loose allowing the motor’s gear to move out of mesh with the lifting gear. It’s this looseness that causes the judder. If you pull the motor gear in tight to the main gear and tighten the mounting screws firmly, on reassembly you should find the fault is cured. It’s a good idea to clear the drains while you are working in that area.
QI left the lights on on my mk1 MX-5 last night and flattened the battery. I tried to jump start the car and now nothing happens, no lights or anything. Please help.
AI’ve had this before and think the problem will be simple to fix. The battery terminals in the boot of a mk1 are very hard to get jump leads connected to and I wonder if you briefly reversed the polarity or shorted the battery terminals. This will blow the 80
amp main fuse located in the fusebox on the driver’s side of the engine bay. It’s easy to see if the fuse has blown by looking through the clear plastic lid of the fuse. It’s not so simple to replace the fuse, however. You must undo the fusebox (disconnect the battery first) and lift it up a little. The fuse bolts in with two short 10mm headed bolts. One is covered by a plastic flap that you need to unclip. Bolt in a new fuse and refit the fusebox. Charge up the battery and re-connect it.
When jump-starting I tend to connect the positive jump-lead directly to the positive battery terminal and then connect the negative jump lead to the battery mounting clamp bracket – it’s a lot easier to access than the negative battery terminal. With a flat battery I would jump-start the car, leave the engine running with the jump starter still connected for a few minutes to let the battery charge a little, then remove the leads. This reduces the power surge when you take the jumpstart off and lessens the risk of damaging the electronics.
QMy mk2.5’s engine light has been coming on, sometimes permanently, and other times it comes and goes. Do you have any thoughts on what might be causing this?
AThis model has an EOBD diagnostic port mounted to the right of the steering column, making electronic fault finding easier than early cars that use blink codes. Often on plugging in we see code PO420 – ‘catalyst system operating below efficiency’.
The next step is to run the car up to operating temperature and measure the exhaust emissions; if the lambda (oxygen content) is around one and the carbon monoxide near zero, the catalytic convertor is functioning correctly.
In this instance replacing the rearmost lambda sensor of the two fitted to the exhaust system and clearing the fault codes will cure the problem.
If the emissions are high then you need to consider replacing the catalytic convertor with the best quality part you can afford. Cheap cats don’t last!
You also need to consider why the cat has failed. Sometimes it’s simply old or damaged through being hit. Air leaks upstream of the front lambda sensor, ignition misfire or bad fuel can all damage the cat. If you don’t find the cause it’s likely your car will be fine for a limited time and the fault will then recur.
QIs there any way I can get more power out of my mk3 without having to spend an absolute fortune?
AWith modern cars not fitted with turbochargers, big power gains aren’t that easy. The manufacturers have already produced very efficient designs that are difficult to improve on.
What we do with the mk3 as a first stage is fit a four-in-toone exhaust manifold such as the Racing Beat or IL Motorsport items. This deletes the front cat, increases efficiency a little and looks great under the bonnet. The second cat still allows an easy emissions pass at MOT time.
You have to install the front lambda sensor into the new manifold after extending the wires a little (they will stretch but we prefer to route the wires better), and weld a new rear sensor mount just behind the remaining catalytic convertor.
Next we fit a K&N air-filter and then get our local dyno guys (Hybrid Tune) to remap the ECU. On 2.0-litre cars you end up with about 180bhp at the flywheel and around 150bhp with 1.8s, plus a torque increase throughout the rev range.
Mk3 folding metal roof deck
Above: mk3’s folding metal roof lifting gear removed from the car and the motor unscrewed from the lifting mechanism – the two items need to be screwed back together very tightly and the juddering should stop
Top: mk2’s EOBD location, above fusebox. Above: rearmost lambda sensor – sticking up from the pipe – can fail and be the cause of engine warning lights. Or, the catalyst may need replacing…
Trying to get the negative (black) jump-lead onto its respective battery terminal in a mk1 is a nightmare: a mistake can blow the 80-amp fuse. Using the battery’s clamp is less potentially hazardous
A four-into-one exhaust manifold gives a little more oomph to a mk3