Misfire when starting warm

my2cta · Post by **my2cta** » Wed Feb 02, 2011 8:23 pm

My 2000 NB has recently started to misfire badly when starting when warm: either when it has been driven and left for a few minutes (e.g. when popping into a shop) or when it has been parked in the sun all day. Either way it starts but generally running on 2 cylinders only, with strong fuel smell (surprise, surprise). Trying to rev the engine doesn't clear it, but the problem will suddenly spontaneously clear and all 4 cylinders then fire up as normal. Can take from a few seconds to 5 minutes to clear.

Mazda thought it might be the crank angle sensor so I had it replaced (needless to say it wouldn't go wrong when in the shop), but that hasn't fixed it. Yesterday it happened again, went to 3 cylinders after a few seconds and then stayed that way: drove with it like that for 25 minutes and just 50m from end of journey the fourth cylinder kicked in! Typical.

One other thing. On the way home yesterday (hadn't been hot sun so started just fine

) the idle speed was up at 1500 rpm every time I stopped at lights, then dropped back to the normal 850 after 5-10 seconds.

Ring any bells? I'd like to know what would be best thing to try next.

Thanks

WideOpenThrottle · Post by **WideOpenThrottle** » Thu Feb 03, 2011 5:25 pm

Sounds fuel related to me.You might have a leak some where?

broomfish · Post by **broomfish** » Thu Feb 03, 2011 6:18 pm

Assuming youve done the basics (Plugs & Leads)?

sprsta · Post by **sprsta** » Thu Feb 03, 2011 6:25 pm

yes i was just about to say peter could do you a deal on a set of plugs and leads.
thats what i would be picking
11 years is pretty good to get out of a set of plugs/leads

i would be picking that your fuel smell is from the exhaust

broomfish · Post by **broomfish** » Thu Feb 03, 2011 7:07 pm

yep, NGK leads and plugs are $115 with free delivery from my website

my2cta · Post by **my2cta** » Thu Feb 03, 2011 8:09 pm

Thanks for replies. I've checked the service history (have had the car for 10 years, always serviced by Mazda) and believe it or not the plugs and leads have never been replaced! Mind you, it has only done around 63,000 kms, used to get used a lot more, but not much in the last few years. I'll try new plugs and leads first and see how it goes after that. Am looking at Peter's site right now

broomfish · Post by **broomfish** » Thu Feb 03, 2011 9:39 pm

Tsk tsk on Mazda for jumping to the Cam sensor without covering the basics first

mazline · Post by **mazline** » Fri Feb 04, 2011 5:11 pm

good chance it's the coil pack,Always a bugga for giving problems on the NB 1800's

SLYDIT · Post by **SLYDIT** » Mon Feb 07, 2011 7:54 pm

yes coil pack is an obvious first point of call....god knows why mazda assumed cam sensor???? maybe they make bigger margins on that part.

that really sucks take it back and tell them you want a coil pack at cost less 10% for being such useless (*^&^^&$^%$

mazline · Post by **mazline** » Tue Feb 08, 2011 9:34 am

Last i checked ,there not that cheap either,Better to see if Ross at MX5 mart has a good second hand unit,If you get one from Mazda and it's not the fault they won't take it back.

WideOpenThrottle · Post by **WideOpenThrottle** » Tue Feb 08, 2011 1:03 pm

I had a problem with one of our NB plug leads pulling out slightly causing it to short to the head....I would push it home again & it would dislodge again causing a some what intermittent misfire.New leads sorted that as it seems the length of the old one shrank slightly.

Donovan · Post by **Donovan** » Wed Feb 09, 2011 1:33 pm

WideOpenThrottle wrote:I had a problem with one of our NB plug leads pulling out slightly causing it to short to the head....I would push it home again & it would dislodge again causing a some what intermittent misfire.New leads sorted that as it seems the length of the old one shrank slightly.

Must be a common thing with the NB's as they had one on the latest Top Gear challenge, and the thing kept on working it's leads loose. Mind you, they were pretty much giving it death.

Misfire when starting warm

Misfire when starting warm

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