NB8B starting and running issues

Engines, Transmissions & Final Drive questions and answers

Moderators: timk, Stu, zombie, Andrew, The American, Lokiel, -alex, miata, StanTheMan, greenMachine, ManiacLachy, Daffy

User avatar
speed freak
Racing Driver
Posts: 873
Joined: Sun Mar 10, 2013 6:39 pm
Vehicle: NB8B
Location: Gold Coast

Re: NB8B starting and running issues

Postby speed freak » Sun Dec 29, 2013 3:33 pm

93_Clubman wrote:
speed freak wrote:Do local auto part stores sell them?

Some of the bigger ones might, but last time I heard a price quote for a new one from Mazda was $150 in 2007.

On cold start what should the idle be? Usually after the base idle is set again cold start will idle at 1500 rpm then drop to about 900 rpm when warm. Now cold start is about 1100 rpm and warm is 800 rpm or so. I was getting idle dip on cold startup too, it would fire and rev up to about 2000 rpm drop to about 1000 rpm then back up to around 1100/1200 rpm for cold start. I cleaned the TB and IAC valve again yesterday (I seem to get a lot of blowby, oil sitting in the TB and intake manifold) now no more idle dip. Start the car this morning, revs up to 2000 rpm and drop to about 1200 rpm.

NA8 here, so from memory not exactly sure what the cold idle speed should be for the NB8B, however there should be a black & white sticker on the inside of the bonnet, which details normal operating temperature idle etc, & might include cold idle, although 1500 RPM sounds close. Normal operating temp idle for NA8 is 850 RPM +/- 50 RPM, so 800-900 RPM.

When the air con is on and lights on etc is that when the IAC valve is working? If so since the 1500 rpm rough spot goes away with air con on does that mean IAC valve works properly? If the base idle is out could that cause starting issues? It seems heat related the cranking but not firing after its been dríven but Iv replaced both cam and crank position sensors, unless that's the EGI relay causing this. Then there is the slow cranking on cold start and just firing up.

My NA6 & NA8s have had no air con or power steering, so I've not delved into what various affects they have. However, as you've advised it's been to Automotive Plus a few times to set base idle - I think it's unusual that base idle has had to be repeatedly set, which to me suggests something else is faulting or going out of adjustment, which subsequently requires base idle to be reset.

Also I looked at my battery and its all black but I couldn't see Panasonic on it anywhere. Didn't take it out though so might be on the side of the battery?

I'm not currently running a Panasonic so can't check, but from memory Panasonic is on it somewhere. That said it sounds like it, especially if it's also got the breather pipes attached at the top of each end.


Cheers mate! $150 is a bit rich lol ebay it is I think for the relay. Automotive Plus are aware of it obviously but they just say now that NB8B's do weird things every so often and they cant find a solution to anything, they just keep adjusting/re setting the base idle every time it gets the rough spot. Although there not aware of the starting problems yet so when they re open Ill be getting in contact with them to see if they can figure it out. I agree though the base idle shouldn't need to be adjusted too often. Ill have a look under the bonnet for the info sticker.

Is the PCV valve usually the culprit for excessive blowby? I assume its not good that there is oil pooling in the TB haha?

93_Clubman
Speed Racer
Posts: 11854
Joined: Mon Aug 08, 2005 11:35 pm
Vehicle: Clubman
Location: Melbourne

Re: NB8B starting and running issues

Postby 93_Clubman » Mon Dec 30, 2013 9:56 am

speed freak wrote:Automotive Plus are aware of it obviously but they just say now that NB8B's do weird things every so often and they cant find a solution to anything, they just keep adjusting/re setting the base idle every time it gets the rough spot.

Indeed NB8s do some weird things every so often, but at least one of the NB8Bs I'm aware of in QLD with what was eventually identified as a water damaged ECU also went to Automotive Plus. Indeed, they may have been the ones to identify the issue with that particular NB8B, & they may have checked your ECU just in case. So, just raising the water damaged ECU issue in case it's not been checked, as it accounts for some of the squirrelly behaviour of NB8Bs out there.

Is the PCV valve usually the culprit for excessive blowby? I assume its not good that there is oil pooling in the TB haha?

Inside of intake manifolds can get very oily, but pooling oil in TB not long after cleaning TB isn't normal, although TB's can need cleaning after tens of thousands of kms. See following ref PCV valve: viewtopic.php?f=29&t=58565&p=739111#p739111

User avatar
speed freak
Racing Driver
Posts: 873
Joined: Sun Mar 10, 2013 6:39 pm
Vehicle: NB8B
Location: Gold Coast

Re: NB8B starting and running issues

Postby speed freak » Mon Dec 30, 2013 2:00 pm

I need to get my mx5 booked in with Automotive Plus in the new year to get the new clutch looked at so Ill let Jason know what its doing again and mention the water damaged ecu as a thought and see if they have checked it. If not Ill check it and replace the EGI relay too. I really need to get these issues sorted as its my daily it frustrates me when it plays up haha.

User avatar
speed freak
Racing Driver
Posts: 873
Joined: Sun Mar 10, 2013 6:39 pm
Vehicle: NB8B
Location: Gold Coast

Re: NB8B starting and running issues

Postby speed freak » Mon Dec 30, 2013 2:13 pm

Another thing I might add about the 1500 rpm rough spot, when its in the warming up process still it wont do it even with the air con off. So from a cold start I normally let it idle for 30 sec or so then take off and only easy on it until its warmed up etc, but you can slow right down to idle and the issue wont occur but as soon as its up to operating temps the issue is there.

93_Clubman
Speed Racer
Posts: 11854
Joined: Mon Aug 08, 2005 11:35 pm
Vehicle: Clubman
Location: Melbourne

Re: NB8B starting and running issues

Postby 93_Clubman » Mon Dec 30, 2013 5:26 pm

Just to give you an idea of what's going on:
93_Clubman wrote:In open loop for cold start & WOT (wide open throttle) or over 4.5k RPM.
In closed loop once operating temp reached up to 4.5k RPM.

Quoted from Miata.net:
"Closed loop = O2 sensor rules, tune should be near perfect
Open loop = All other sensors rule (O2 is ignored) tune tends to be rich.

If the TPS is not closed or wide open the ECU looks to the CAS & AFM to see if you're cruising.
If so, it goes into closed loop with the O2 sensor & ignores the others.
If you accelerate, it goes open loop & uses all the sensors to set the tune (rich).
When you close the throttle above 2K RPM fuel is cut altogether."

viewtopic.php?f=29&t=36426&p=689325#p689325

Manga also described it well relatively recently:
manga_blue wrote:An NA8 runs in closed loop mode when revs are below 4500 and you're just using light throttle. In closed loop mode the ECU uses the O2 sensor to help it set mixture.

It runs in open loop mode above 4500 or when you're giving it at least half throttle. In open loop mode the ECU only uses its internal fuel map to set mixture and the O2 sensor is not used.

viewtopic.php?f=29&t=60066&p=755458#p755458

User avatar
speed freak
Racing Driver
Posts: 873
Joined: Sun Mar 10, 2013 6:39 pm
Vehicle: NB8B
Location: Gold Coast

Re: NB8B starting and running issues

Postby speed freak » Mon Dec 30, 2013 8:03 pm

Cheers that makes sense to me now. So does that mean the O2 sensor could be the problem?

93_Clubman
Speed Racer
Posts: 11854
Joined: Mon Aug 08, 2005 11:35 pm
Vehicle: Clubman
Location: Melbourne

Re: NB8B starting and running issues

Postby 93_Clubman » Tue Dec 31, 2013 12:23 am

Unserviceable O2 sensor usually just results in running rich, ie running in open loop all the time. However, what you could test is what happens if you disconnect the O2 sensor prior to cold start, & drive until operating temperature is reached to see what then occurs as you continue to drive.

Btw, noticed in your other thread that the inside of the TB bore appears to be missing the brown sealant which allows the throttle plate to seal against the inside of the TB bore. The sealant could have been easily removed when cleaned by a previous owner. Missing sealant should initially result in higher uneven idle until adjusted down, but even after adjustment unevenness should persist.

User avatar
speed freak
Racing Driver
Posts: 873
Joined: Sun Mar 10, 2013 6:39 pm
Vehicle: NB8B
Location: Gold Coast

Re: NB8B starting and running issues

Postby speed freak » Tue Dec 31, 2013 5:33 pm

Could you tell me roughly where the o2 sensor is located? Iv tried looking for it another time but couldn't see under the car properly but if I have an area to look for it I may be able to find it. Interested to see what happens when its unplugged. If its unplugged it wont run lean will it? Rich I don't care about but don't want it to run lean. I usually get around or close to 500 km to a tank of 98 so it seems to be running normal in that aspect.

Is there a sealant I can buy to put back on the butterfly valve? I suppose if it doesn't seal properly maybe the IAC valve is fighting with the TB when off throttle? Or do I just find another TB with the sealant still there?

ralt
Fast Driver
Posts: 423
Joined: Thu May 19, 2011 11:10 am
Vehicle: ND - 2
Location: brisbane

Re: NB8B starting and running issues

Postby ralt » Tue Dec 31, 2013 9:33 pm

Hi.
Use nail polish. Apply it around the edge of the butterfly and when tacky open the butterfly hold open until dry. This should fix your high idle.

93_Clubman
Speed Racer
Posts: 11854
Joined: Mon Aug 08, 2005 11:35 pm
Vehicle: Clubman
Location: Melbourne

Re: NB8B starting and running issues

Postby 93_Clubman » Wed Jan 01, 2014 9:51 am

speed freak wrote:Could you tell me roughly where the o2 sensor is located?

Left foreground is exhaust header heatshield with O2 sensor to the right:
Image

Bottom of exhaust header heatshield to the left & O2 sensor to the right:
Image

Probably easiest to disconnect O2 sensor at the connection block at the rear hotside of the engine, ie the connector block which the blue etc wire goes into:
Image

User avatar
speed freak
Racing Driver
Posts: 873
Joined: Sun Mar 10, 2013 6:39 pm
Vehicle: NB8B
Location: Gold Coast

Re: NB8B starting and running issues

Postby speed freak » Wed Jan 01, 2014 5:32 pm

Cheers guys! Ill give that nail polish trick a go and see if it helps.

I take it there is only the one o2 sensor? Looks pretty easy to get too, I always wondered what that connection was on top of the valve cover, now I know its the o2 sensor connection. Mine is held together by a zip tie lol been like that since I bought it.

User avatar
zero00
Speed Racer
Posts: 3248
Joined: Mon Apr 12, 2010 6:54 pm
Vehicle: NB8A
Location: Sunshine Coast Queensland

Re: NB8B starting and running issues

Postby zero00 » Wed Jan 01, 2014 10:46 pm

My NA used to do that SF, funny, it still does occasionally but after running for a while it's all good - when I first got it almost 3 years ago it would 'flare' between 700-2000 or simply stall at lights!
Roger D-SUNSHINE COAST
2000 NB8A-LP 69.1248|QR Clubman 71.9235|QR Sprint 68.1412
1989 NA6 B-SPEC #77|Toyota GTS86 MT

93_Clubman
Speed Racer
Posts: 11854
Joined: Mon Aug 08, 2005 11:35 pm
Vehicle: Clubman
Location: Melbourne

Re: NB8B starting and running issues

Postby 93_Clubman » Thu Jan 02, 2014 8:27 am

speed freak wrote:I take it there is only the one o2 sensor?

Yeah, on the Aust Domestic Market NB8Bs, but believe other markets have more than one: viewtopic.php?f=55&t=56856&p=716687&hilit=o2%2A+sensor%2A+nb8b#p716687

User avatar
speed freak
Racing Driver
Posts: 873
Joined: Sun Mar 10, 2013 6:39 pm
Vehicle: NB8B
Location: Gold Coast

Re: NB8B starting and running issues

Postby speed freak » Thu Jan 02, 2014 8:05 pm

Cool thanks again!

I done the nail polish mod on the TB butterfly this arvo so Ill see if that makes a difference tomorrow. Also I should have a new EGI relay ordered on ebay in the next day or 2.

On my weekend Ill disconnect the o2 sensor plug and go for a cruise and see what happens.

I know my battery is still the oem Panasonic one, can I just get a normal replacement from autobarn/super cheap etc?

Apart from getting the ecu checked for water damage that's all the suggestions covered I think from memory. Hopefully one or a couple of those will resolve these issues, I love my mx5 but its really annoying me lately with doing all these random things. It now has a squeak/squeal on startup now too.... it never ends lol. I cant think of anything else to check/replace that would fix these issues.

Automotive Plus open again on Monday so Ill give them a call and have a chat with them too, fingers crossed.

Thanks to everyone who has posted a suggestion and especially 93 clubman for all your continued help, I greatly appreciate it :)

93_Clubman
Speed Racer
Posts: 11854
Joined: Mon Aug 08, 2005 11:35 pm
Vehicle: Clubman
Location: Melbourne

Re: NB8B starting and running issues

Postby 93_Clubman » Fri Jan 03, 2014 7:42 am

speed freak wrote:I know my battery is still the oem Panasonic one, can I just get a normal replacement from autobarn/super cheap etc?

The OEM Panasonic is a vented (a pipe from the top of both sides) AGM type battery. There are many options as you'll see from the following, so you'll need to research from the following & decide what you think is best taking into account all your circumstances:
viewtopic.php?f=77&t=55444
viewtopic.php?f=55&t=55595
viewtopic.php?f=55&t=55260
viewtopic.php?f=55&t=51698
viewtopic.php?f=55&t=50299
viewtopic.php?f=55&t=49128
viewtopic.php?f=19&t=45988
viewtopic.php?f=55&t=48470
viewtopic.php?f=57&t=47228
viewtopic.php?f=55&t=28764
viewtopic.php?f=55&t=43729
viewtopic.php?f=18&t=25325
viewtopic.php?f=55&t=30278
viewtopic.php?f=55&t=39216


Return to “MX5 Engines, Transmission & Final Drive”

Who is online

Users browsing this forum: No registered users and 92 guests