NB8A rough idle.
Moderators: timk, Stu, -alex, miata, StanTheMan, greenMachine, ManiacLachy, Daffy, zombie, Andrew, The American, Lokiel
-
- Fast Driver
- Posts: 109
- Joined: Tue Nov 27, 2007 8:58 am
- Vehicle: NB8A
- Location: Berwick, Melbourne
NB8A rough idle.
Im trying to work out what could be wrong with my mx5 at the moment. When its been running and then stopped for maybe 1-2hrs i go to start it again and it feels like its only running on 3 cylinders(rough idle, no power) for maybe 10-20secs and then kicks to life again and runs normally. If its been off over night it starts fine. Same as if its been only stopped for maybe 20mins. Its only for that 1-2hrs of sitting there that it seems to develop this. At first i thought spark leads but figured if that was the case then it wouldnt really matter how long the car had been sitting there. Any ideas? oh and it never stalls when its running rough.
-
- Forum Guru
- Posts: 4897
- Joined: Mon Apr 24, 2006 7:27 pm
- Vehicle: NA8
- Location: Moruya, NSW
Re: NB8A rough idle.
I tend to blame coilpacks for everything but usually when it's coilpacks the problem happens within a few minutes of stopping. What happens is that when you switch the engine off the coolant stops flowing and the stored heat around the exhaust ports and combustion chambers spreads out, heating the coilpacks to something a bit hotter than normal running conditions. If the coilpacks are getting old and dodgy then this may affect them for 10 or 20 minutes after you stop, but not an hour or two later.
Can't think what else it might be. ECT sensor not returning to correct reading: when you restart the engine is cold but ECU is told it's hot? Unlikely. Heat soak in IAT sensor? ECU thinks the incoming air is hot and adjusts mixture down to lean? Has there been any change to IAT sensor position or exhaust shielding?
Can't think what else it might be. ECT sensor not returning to correct reading: when you restart the engine is cold but ECU is told it's hot? Unlikely. Heat soak in IAT sensor? ECU thinks the incoming air is hot and adjusts mixture down to lean? Has there been any change to IAT sensor position or exhaust shielding?
’95 NA8
-
- Fast Driver
- Posts: 109
- Joined: Tue Nov 27, 2007 8:58 am
- Vehicle: NB8A
- Location: Berwick, Melbourne
Re: NB8A rough idle.
as far as im aware its all pretty standard. i'll have a look at some of the sensors and see if anythings amiss
- Black_Penguin
- Racing Driver
- Posts: 726
- Joined: Thu Jun 03, 2010 5:30 pm
- Vehicle: NB8A
- Location: Ulladulla, South Coast NSW
Re: NB8A rough idle.
Leaky O-ring on an injector? Fuel will leak past and sit in the inlet, when you start it it will run pig rich on one cylinder until it is all drawn in. And over night it will evaporate away.
My Garage Thread WP 1:16.1 SMSP South 1:10.0 WSID 15.6
-
- Fast Driver
- Posts: 109
- Joined: Tue Nov 27, 2007 8:58 am
- Vehicle: NB8A
- Location: Berwick, Melbourne
Re: NB8A rough idle.
Would the o-ring be leaky or the injector itself?
- Black_Penguin
- Racing Driver
- Posts: 726
- Joined: Thu Jun 03, 2010 5:30 pm
- Vehicle: NB8A
- Location: Ulladulla, South Coast NSW
Re: NB8A rough idle.
Could be either, wouldn't hurt to get both checked.
My Garage Thread WP 1:16.1 SMSP South 1:10.0 WSID 15.6
-
- Speed Racer
- Posts: 12006
- Joined: Mon Aug 08, 2005 11:35 pm
- Vehicle: Clubman
- Location: Melbourne
Re: NB8A rough idle.
Ash, some ideas here: viewtopic.php?f=29&t=47266
-
- Fast Driver
- Posts: 172
- Joined: Tue Feb 24, 2009 10:59 am
- Vehicle: NB8A
- Location: Radelaide SA
Re: NB8A rough idle.
hey sweep, I've had a similar issue intermittently for some time, my coilpacks have checked out OK and I've done plugs and leads. The injector idea was suggested to me and I'm yet to check it out (not sure how much labour it would take to check all 4). Mine will occasionally run on what seems to be 3 or 2 cylinders after starting when sitting for anywhere between 30 minutes and 6 hours, but hardly ever from dead cold. Sometimes it clears in a couple of seconds, very occasionally it doesn't clear and I switch it off & restart a few minutes later. It only happens once every few weeks or even less, and is very random so almost impossible to replicate at a workshop when the mechanic only gets one or two shots at it. I've been driving it most days for the last week and it hasn't happened at all. It never has any problems whilst driving or going up hills under load, which ruled out some of the electrical problems that can happen, its only when starting the engine. I'm going in for a service soon and I'll ask about geting the injectors checked.
Was: 1988 Corolla 4A-GE Twin Cam, 1991 Laser TX3, 1995 Peugeot 306 S16, 2003 Astra Sri Turbo, 2007 SP23 Lux
Now:1999 NB8A, 2011 Outlander VR-X
Now:1999 NB8A, 2011 Outlander VR-X
- dimarg
- Driver
- Posts: 68
- Joined: Thu Feb 17, 2011 3:10 pm
- Vehicle: NB8A
- Location: Melbourne
Re: NB8A rough idle.
Hey mate had the exact same issue! Ran through some injector cleaner and hasnt happened since.
Probably the cheapest option so worth a try at least?
Probably the cheapest option so worth a try at least?
-
- Fast Driver
- Posts: 109
- Joined: Tue Nov 27, 2007 8:58 am
- Vehicle: NB8A
- Location: Berwick, Melbourne
Re: NB8A rough idle.
Yeah was thinking to try injector cleaning. Can't hurt anyway!
-
- Fast Driver
- Posts: 109
- Joined: Tue Nov 27, 2007 8:58 am
- Vehicle: NB8A
- Location: Berwick, Melbourne
Re: NB8A rough idle.
Well took the car to the shops and then started to go home and it wouldn't come good and only ran on 2 cylinders. Back to the Mazda dealer then and get them to fix it under warranty hopefully. I'm thinking its the coil pack as its 2 cylinders not just one not firing.
-
- Fast Driver
- Posts: 109
- Joined: Tue Nov 27, 2007 8:58 am
- Vehicle: NB8A
- Location: Berwick, Melbourne
Re: NB8A rough idle.
Turns out it was the coil pack aft all. Lucky the dealer replaced it under warranty! Saved myself $500!
-
- Fast Driver
- Posts: 280
- Joined: Sun Jan 15, 2006 5:11 pm
- Vehicle: NB8A
Re: NB8A rough idle.
yeah was going to say coil packs.
exact same thing happened to me. they aren't cheap but hopefully only need to replace once.
exact same thing happened to me. they aren't cheap but hopefully only need to replace once.
NB8A
Return to “MX5 Engines, Transmission & Final Drive”
Who is online
Users browsing this forum: No registered users and 26 guests