The MX5 NB Start/stop curse?

Technical Area Engine, Transmission, Exhaust etc
2

I’ve been traulling the net for the past few days due to some weird probs with my 99 nb. I’m unsure of it’s exact specifics as I recently purchased it however I didn’t get an owners manual. It’s a build date 98, compliance date 99 NB.

I have searched the forums a lot, checked youtube and other sites, all mentioning a similar problem, but no clear results except for a few things that I don’t understand the process to test.

So here’s my problem;

It is starting, 2-3 secs run time then dies. It does this a couple of times then wont start at all, just cranks. 2 days later and it started again, ran very low revs, foot on the gas and it ran great, occasionally dropped to low revs then went back to norm and ran great for a few mins, I even drove it around a little but kept the revs up a tad, the thing I noticed though was a red light in the top right of my dash - (car shape with a key in it) was on the whole time the car ran.

After a few more starts though it returned back to starting, running then dieing, now it just cranks again however the red light doesn’t come on anymore. The first time this happened I noticed that the red light would flash on and off (not steadily, more of a random pattern) while the car’s ignition was on but not running.

I got the car 3-4 months ago, it came with only a normal key, no immobilzer control or key with a chip (which I’ve read, neither came with the 99 NB’s anyway) Which makes me wonder what the light stands for, I can’t find any info anywhere on the net about this light, I don’t have an owners manual and the only manual on the net I have found doesn’t explain it.

One other thing to note is that I recently moved to a house with no cover for the car, it has been pouring down with rain here for a week and the car 's passenger side(left) has flooded. I guess the rubber seals have shrunk a little. So I am drying it all out waiting on a new roof and seals but there was a lot of water in that side, then a week later the engine starts playing up.

I guess what I’m after is:

1: What is the red light for (car shape with key in it) If it’s immobilzer does that mean I need to get a remote for it?

2: How do I actually test the fuel pump to see if it’s running when the car is. I’ve read that I should Ground the F/P and try it, how do I do that? in detail please :)  (it makes a running noise for a short time when I turn the car off, it also has fuel in the lines from the pump end).

3: How do I see if fuel is actually making it to the engine? from the engine bay end, would this be easier to discover than testing the fuel pump or is there a filter some where that I could check?

3: What should I clean the MAF with? special MAF spray like the CRC brand one maybe?

I have noticed the symptoms are virtually identical and a common occurance in peoples NB’s however the fix always seems different.

I’m still in the process of trying a few options like cleaning the MAF and trying to test the fuel pump.

Sorry if this is another post of the same problem, I just haven’t been able to find enough info explaining details in lamens terms on how to troubleshoot.

Obviously I’m thinking to take it to a mechanic, but if I can avoid the towing/repair costs by doing itmyslef, then I’d be a happy man.

Any help would be amazing thanks.

Gavin

3

Just some more info for you all that I gave to another member in response to his question about the problem occuring after the roof leaked…

"Thanks Geoff that is so helpful.

As far as the flooding goes, the starting problem happened a week after the left hand foot well filled with water. The leak I believe is coming from the front left corner where roof meets the top front part of the side window (hope that made sense)

I’ve checked under the dash around the connections and it all is dry, can’t see any signs of moisture except for the the roof lining and latches, including left side carpet. Right side is dry everywhere.

The car was running fine while it had the water build up in it. I got rid of the water, dried it all out, patched the leak and it kept on going fine. Then 3 days ago when we got that massive amount of rain the leak broke through again but the car ran fine that day, it was the next morning (tuesday just gone) when it started with the engine problem. After 4-5 attempts of it starting, running 3-4 secs, dieing it then went into crank only mode.

This morning, I since have fiddled with the fuel pump, unscrewed it, disconnected the lines but I didn’t take it out of the tank. I also pulled the air intake apart and blew air over the sensor in a vain attempt to remove debris if any. I did all this after disconnecting the battery. When I put it all back together I tried to start it again, sucess it started, however it ran barely under it’s own power for over a minute. I then revved it and held the revs for a bit and all ran normal, when returning to idle it would run just fine but occasionally dropped to barley running for a 3-4 seconds then go back up to normal idle.

It wasn’t Tach jumping as I’ve seen in some videos, just occasionally dropping in power.

I stopped it then started it again running mostly fine, after the 3rd test it then started, ran 3-4 secs, died. 4th attempt, it just cranks.

I’ve disconnected the battery again and will go test it now before I send this email back, sneaky suspistion that if it is an immobilser/anti theft thing im unnare of, no power for a while may reset it. Just a guess.

I’m back, no change still just cranks."

4

 Hi Gavin,

Here is the electrical component locations for 2005 Mk2.5 which may give a clue,  http://www.mellens.net/mazda/Mazda-Miata-2005/electrical_component_locations.pdf

imobiliser and fuse block under the dash left side (on the LHD car anyway).

and the 1999-2001 service manual, http://www.mellens.net/mazda/Mazda-Miata-1999-2001.pdf

Other stuff also there, http://www.mellens.net/mazda/index.html

(big files, far quicker to right click a menu link and choose “save target as” rather than opening them in browser first)

5

The engine ECU is at the front of the passenger footwell, has this got wet?

Alan

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That’s where I was headed too Alan. The rain over here has been typical tropical storms for a few days and Gavin is a few ks away from me.

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Thanks for the info Rich, some valuable stuff i’ll be hanging onto right there.

Thanks Alan, I did look high up into there area where the ECU is but there wasn’t any signs of water around that part. I will double check the ECU itself tomorrow.

In a turn of events though, I went out later today and tried it again, car started and ran perfect without any real noticeable rev drops, just slightly and rarely. I gave it some on and off action and the whole process started again, this time however the little warning light with the car shape and key came on again. A car dealer friend of mine said it sounds just like a faulty chip in the key, this seems like a logical explanation as others have found that to be the problem.

I’ll go in tomorrow and get a new key, doesn’t hurt to have a 3rd. Just seems weird that both keys have become faulty at the same time.

My thought is that the immobiliser was not working hence never having a problem with it before, however, wether rain or something else it has fired up again but only works time to time.

I will check ECU and key and post my results, still wish I knew what that warning light was for, seems logical it’s an immobilser.

Keep you posted…

8

 Hi Gavin,

That light, the car with a key in it,

the following is from the Mk3 2007 manual and is same on our 2005 Mk3 and 2006 Mazda 6,

9

 The immobilizer is starting to break down/fail, common fault now on the UK specs.

It’s the lucas box behind the dash, just a little smaller than a cig packet, but the whole system is connected together, i would have a word with your local dealer, and see if they can just reprogramme a new one, and fit it, other wise it is a scrape yard, and time to get your hands dirty, easy enough to do a swap of the system, it’s just the cost of what you can find it for.

M-m

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Your a legend mate, I have spent ages trying to find out that info.

 

Thank you so much, very helpful.

11

Thanks for the info, I was wondering where it was hiding. Wish I could just get rid of it all together so I didn’t have to bother with it.

I just came back from the dealer who wanted $150 (approx £75) to get a new key, cut & programmed.

He did say that I should bring the car in first to diagnose the immobilzer before I worried about keys.

Thanks for the advice

 

12

 It’s not the key at fault, its the immoberlizer box, a have done a couple of swaps, if you do a search on here ,you should find some info from me and the owners i have helped with this,there was an owner on here that said that he went to his local dealer and they reprogrammed just a new immobilizer box and fitted it to his Mx?, the price was not dear ,but i can not remember just how much that was, a full system from a working Mx of the same year and engine, with the same code on the ECU from a breakers should be around the £300 mark depending on where you go, prices will be different in OZ, they ask stupid prices for stuff over there.

If you need any pointers ,give me a shoutThumbs up

M-m

13

Thanks for that,

The hard part is finding one from a wrecker over here, few and far between. I have got a guy trying to track one down for me so hopefully that works out.

The Mazda dealer has told me $525 (approx £250) for a new one so I may just have to bite the bullet and go that way.

Thanks for all the info, it has been fantastic.

Gav.

14

 Gav,

Two things; one, a secondhand box may be nearing the end of its life too. A similar situation existed with Mitsubishi ecu a while back, £1000 for a new one and all the old ones dead at 10 years, so a new one may be best option if you intend to keep the car. Two, it might be worth opening up the box and seeing if it can be fixed. Just a chance it may be a failed electrolytic capacitor (just about the most unreliable electronic component known to man). These provide smoothing and local power supply and come in varying qualities/lifespans. Cheapest pack up after a couple of years in cheap TVs, best work for 30 years+ in telecoms. I’ve just fixed my 6 year old pc motherboard with a similar erratic fault, 2 caps blown their ends, simple visual inspection and replacement. Your box may or not be potted (in resin) though. Maybe ask a TV/radio repair shop to take a look if you’re not familar with such.

(These caps hate ripple and heat. Always keep the car battery in good condition as that is the primary smoothing component for the whole electrical system. The DC off the alternator is very rough pulsed and a poor battery will cause stress to the alternator and all the electronic systems by not smoothing the DC. Similar reason for never running the car without the battery, it may run but all the electronic parts will be getting a hammering.) 

15

Thats a good point Rich, the only reason Im looking at a cheap alternative is that the roof and seals have to be done at the same time and unfortunatley they are not cheap here at all.

Thansk for the info in a possible self repair, Ill check it out and see what I can find. Thanks for your help, I wish more people out in the world were as helpful as you guys.

Gav

16

Hi Gav

Did you try Danny/Richard at http://www.mx5plus.com.au/index.php they would be my first call