Newbie to the forum and need help with my NB

jakdh · Postby **jakdh** » Mon Jul 07, 2014 6:41 pm

Thanks and will do Ill try both first I think and then take it from there if it is a ecu issue or a wiring harness ect. Once I have these parts and installed them I will see how the car goes and ill keep it posted on my luck! again thanks for the help I can only hope it is something reasonably cheap and simple

93_Clubman · Postby **93_Clubman** » Tue Jul 08, 2014 10:50 am

jakdh wrote:...my 2000 year mx 5 NB.
I took it to a mechanic which said the ecu had water in it so the ecu got rebuilt which it was ether that or a new ecu.

At the moment with the stalling thing the other day I nearly crashed because of it stalling and having no breaks at 70...

You mention it's a 2000 NB8 - late 2000 was when the NB8B was introduced - prior to that it was the NB8A - which do you have? The VIN on the engine bay side of the firewall will show JM0NB30P1 for NB8A or JM0NB30P2 for NB8B - it's worth clarifying this as there are more & different issues that cause problems in the NB8A to the NB8B.

Btw, no brakes at 70 is another issue altogether!

jakdh wrote:I thought the mechanic would straight up replace it but seeing as it was cheaper to rebuild I decided to do that instead.

A water damaged NB8 ECU that's subsequently been dríven with would not be cheaper to rebuild than an perfect condition second hand NB8 ECU, unless the mechanic was using the price of a new NB8 ECU. Even then a water damaged NB8 ECU that's subsequently been dríven with would be a nightmare to rebuild, & I'd argue it would need to go to a electronics specialist to be done comprehensively, ie fully tested before & after etc.

speed · Postby **speed** » Tue Jul 08, 2014 2:15 pm

Think the op stated that the brake issue was due to the car stalling.

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jakdh · Postby **jakdh** » Thu Feb 26, 2015 11:18 am

Hey again sorry for the length of time with replying to this post but I thought I would update it in case anyone was having similar issues, So the issue with my mx5 was a lot of things but Ill start of with the beginning, after all these issues the car sat in my driveway for 6 months while I saved for parts to fix it, I took it to a mechanic about water in the ecu and he changed a capacitor in that ecu for $1000 and said the ecu should be fine...... biggest waist of money and basically took it to a family friend who is an auto electrician, he told me I got ripped of so that's why I said it was a waist of money. In the end it was a $60 dollar cps which made it stop stalling and running and idling bad, the next stage was to check spark with new spark plugs and leads which have been installed and made the car run a little bit nicer when cold but I still had the poor idle issue when it was cold but not while it was warm, it did everything absolutely perfect when she was warm so that's when I replaced the co2 reader in the exhaust and that alone has stopped the bad idle when she is cold so I am soooooo happy to have it working again, its even reliable enough to be my daily to work again which makes it so much nicer to get to work and back in a convertible.

I also mainly wanted to say thank you to the people who helped me and posted in this post as most mechanics had no idea what the issue is and I spent soo much money for them to try and figure it out when all the information that was needed was on this forum, I should of asked here first if anyone had similar issues and believe me I will not make the same mistake in trusting mechanics to do work on my car, charge me thousands of dollars in labor to not fix the issue when I should be the one taking care of and keeping track of my own car. Hard lesson learnt but I will not make the same mistake again with any car in the future.

Not ragging on mechanics ether as quite a few of my friends are mechanics but there is just a few that ripped me of and said they did stuff for x amount then I take it to somewhere else and they say I got ripped off so that's my lesson learnt and again thank you for the people that helped me on this topic.

Cheers.

Mr Morlock · Postby **Mr Morlock** » Thu Feb 26, 2015 9:28 pm

You have raised some matters of concern. It's pretty clear that what you paid was excessive. I am not sure why you would have authorised or accepted such a charge. Mechanics ie businesses normally require an authorisation and acceptance before proceeding. You may well be able to seek free advice and maybe action from a State run claims tribunal.

speed · Postby **speed** » Fri Feb 27, 2015 8:24 am

Glad you are back on the road. I'd say that mechanic owes you about $900 but you've also learned a valuable lesson.

Best of luck mate

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jakdh · Postby **jakdh** » Tue Apr 19, 2016 6:56 pm

Ok so posting on a old post now but in case anyone has similar issues, my stalling when hot issue was the tps, the cold idle issue has not been fixed but I'm slowly doing the work my self. An attempt to fix the cold idle issue was cleaning the idle air control valve under the tb at the front, cleaning the tb its self and replacing the iacv gasket and tb gasket. All the cleaning was done with Nylon trottle body cleaner not carb cleaner so I didn't remove the wax surface of the tb. Adjusted idle according to the specific instructions on Miata.net. Changed spark plugs, leads, coil pack. Bought a new ecu not because of the cold idle issue but because of it getting wet when my car was flooded. Changed 02 sensor.

My thoughts are now leading me to the green coolent temp sensor on the rear of the engine underneath the coil pack. Reasoning is from what I have read is the lambada sensor is only used in closed loop above 5k rpm so the rest of the sensors are used from idle and up to 5k.

The coolent temp sensor from what I have read is what controls the fuel and timing on idle when cold, the car idles fine when first started at 1.5k then 1.3k then 850-900rpm but when i come to a stop while the car is cold still it idle drops like 200rpm and also when the car is warm, if I stop the car and turn it off, fuel up at a servo and start it gain it idle dips again but then idles like a champ. To me it seems like the car is reading the water temp wrong because of the information I have read. I have a new water temp green sensor for my car, struggling to find time and the fact that it looks like not a fun job removing the coil packs to get to the sensor.

Hope my thought process and information is correct and I can fix the out standing and hopefully last mechanical issue with this car. Also hope that this can help someone one day because when I first got the car I was pretty lost with the whole thing and fixing problems like this. Also hope I am not bothering anyone with posting in this thread again and thanks to everyone for helping me out with the information on my car and in general helping me when I first got the nb8a. Greatly appreciated!

93_Clubman · Postby **93_Clubman** » Wed Apr 20, 2016 12:03 pm

jakdh wrote:hope I am not bothering anyone with posting in this thread again...

Definitely not - it's your thread so post away.

jakdh wrote:hope that this can help someone one day because when I first got the car I was pretty lost with the whole thing and fixing problems like this.

Precisely why you should post about your experience.
Great to hear that you've experienced some improvement following replacement of a number of items. Unfortunately the NB8 (especially the 1998 to Sep 2000 NB8A) does experience a number of difficult to diagnose issues, which in your case was also not helped by the ECU & wiring loom getting wet. Hopefully the new CTS helps, but also worth very, very carefully cleaning the MAF with MAF or similar cleaner, if you haven't already. Good luck!

jakdh · Postby **jakdh** » Wed Apr 20, 2016 12:25 pm

Yeah definitely an improvement but still got to fix the cold idle issue, at least it's not stalling while warm any more! Definitely need to try to clean the MAF at some point but still dreading taking the coil pack of to get to the cts sensor, or find someone that can fit their hand down their between the firewall and the head. I'll see how I go and hopefully find a fix for the rough idle issue!

speed · Postby **speed** » Wed Apr 20, 2016 6:18 pm

Coolant sensor is not hard to change, unless the NB is further back than a NA6.

Keep us posted

manga_blue · Postby **manga_blue** » Wed Apr 20, 2016 7:19 pm

There's less room behind a BP engine but it's still not that bad once the coilpack is off.

Congrats on learning your way around all the sensor functions. This little thread may help you a bit more:
viewtopic.php?style=3&f=29&t=69778&p=859337&hilit=Switch#p859337

jakdh · Postby **jakdh** » Wed Apr 20, 2016 8:44 pm

Definitely will post it up once I find the cause to the idle dip! Yeah the coolent sensor should be alright when I get the coil pack out of the way. Hopefully my knowledge is correct with all the sensors. I had a feeling it was the clutch switch but have had it checked by a mechanic who is a close friend, said it was working and all good. Cheers for the thread post but!