mx5cartalk.com

Hi all,
My '07 NC has developed a bit of a rattle from the engine. Seems to occur when the engine is warm/hot and after/during 2 or 3 short trips. I took it to my dealer and, predictably, they said they couldn't hear the problem. So I took a technician with me for a drive, with the roof down and found a small hill - drove up it in 2/3rd gear (its an auto) and at around 2,500-3,000 rpm hey presto, rattling noises. the technician said it was pinging/detonation and to try different fuel suppliers. I had always run it on Caltex 98 to that point. started using different fuels but made no difference. I'm not really happy with this 'advice'. My girlfriend's beat up old Lancer has covered 170,000 km and pulls like a freight train with no pinging at all, yet my pampered Mx5 sounds like a diesel taxi some times!

I have read that pinging/detonation can occur as a result of carbon build ups in the fuel injection system and manifold and so I was thinking of getting the 3 in 1 fuel injection clean from lube mobile. its nearly $200 though, so I thought I would check here first.

Anyone got any suggestions or advice?

thanks
Magnum

The dealer can test for det from the ecu.

Your dealer is dishonest.

FirstiI would empty the tank and fill with 10L of BP ultimate. Then add a race strength octane booster like nulon or wynns.

The re test. If you still here something it's 99 percent not det.

Dann

Okay, thanks Dann, I'll give that a go. cheers.

take the vehicle to another specialist ie 2nd or 3rd advice may well get it sorted out. Forget emptying tanks and miracle additives- your car is designed to run on a certain grade of fuel- its not a nitro dragster. A comparison to other vehicles is not relevant- rest assured it should run perfectly so there must be cause and a cure.

You may find that the problem is the serpentine belt tensioner and/or idler pulley. Replacing those cured my engine rattles off idle and under similar circumstances to yours. I only ever use 95 RON (mostly Caltex) - no pinging/detonation and I have a steep hill to drive up to my house. See the NC technical section. http://mx5cartalk.com/forum/viewtopic.php?f=79&t=54540

Yep mine has a similar described rattle. I changed the idler pulley and it reduced it. Most of the noise is coming from the tensioner. I've got to purchase one

Where are u located??

I'm in Brisbane, southside
Thanks

Having just been to a Tech night with the Club at Nulon they said their octane boost if added to 91 octane fuel will give you a rating of 98 but if you add it to 98 octane fuel it only boosts it to 99 but I doubt the octane is the problem because as John said, we can run on 95 and you’re on 98.

One of the Nulon products, Fuel System Cleaner (about $23), will clean your injectors and the carbon deposits from the combustion areas, far cheaper than getting Lube Mobile to come out and add it for you. If you have deposits that will fix it, so it’s probably not a bad idea to throw a bottle in anyway.

On pinging, the NC’s computer will automatically change the spark advance if pinging is detected due to poor fuel. Check that idler pulley.

Redline SI-1 fuel additive is also good stuff for about $20:
http://www.redlineoil.com.au/product-in ... ladditives

There's also Subaru Upper Engine Cleaner for about $20, which can be sprayed into a top of engine vacuum line as opposed to being added to fuel.
But check if other NC owners have used it successfully:
viewtopic.php?f=29&t=27600
viewtopic.php?f=29&t=36182
http://www.miata.net/garage/tsb/s004_93.html

Once you have it sorted, as a bit of preventative maintenance, go on a few long drives with your local MX-5 club and take it out of full auto so you can let the engine rev out a bit.

Okibi wrote:let the engine rev out a bit.

You mean an Italian tuneup?

I reckon JBT/CB is on the money for the cause. I suspect we are talking of a low KM 07 model.with sub 100,000KM Modern cars do not suffer pinging unless there is a fault and its very unlikely to have anything to do with fuel if it has been persistent. I also would not pay much attention to claims made about additives. It makes no sense to consider anyone needs an additive to a modern MX5 to avoid pinging. Upper engine cleaner- I would not consider this unless someone is desperate- how many KM's?
Best go elsewhere to a Mazda or well informed business and pass on the advice from JBT to add to the mix.

I'm not suggesting to use an additive to solve the problem, but to confirm it.

Dann

Mr Morlock wrote:I reckon JBT/CB is on the money for the cause. I suspect we are talking of a low KM 07 model.with sub 100,000KM Modern cars do not suffer pinging unless there is a fault and its very unlikely to have anything to do with fuel if it has been persistent. I also would not pay much attention to claims made about additives. It makes no sense to consider anyone needs an additive to a modern MX5 to avoid pinging. Upper engine cleaner- I would not consider this unless someone is desperate- how many KM's?
Best go elsewhere to a Mazda or well informed business and pass on the advice from JBT to add to the mix.

There's always the possibility of a knock sensor being faulty - that would stop the ecu from pulling back the timing if it started to ping. I've also had some serious problems with deposits forming in the combustion chambers with bad batches of fuel - both times from Shell V-Power sold in VIc and in both instances leaving little round iron-like nodules on the head and all over the spark plugs to the point where the plugs could no longer spark. BP Ultimate ultimately cleaned all that out for me. I wonder if anyone has checked the plugs lately?

Magnum wrote:I'm in Brisbane, southside
Thanks

You can always bring it over to my place and I'll have listen for you. I'm over at Jindalee. PM me if you'd like to take up the offer.