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Recently just on startup, the idle is rough and the rpm drops down below 500, engine shake pretty violently and can smell petrol fumes from the exhaust.... I tried changing the spark plugs and it stopped for a while.... but it happened again starting the car up from the office

Could it be the leads, MAF sensor or coil pack?
Anyone had experienced this before?
Might go and buy a set of new spark plug leads this weekend

-Kelvin

In the absence of further information, new leads won't hurt.

EGG80X wrote:Anyone had experienced this before?

Yes, but only when warm - mine had a faulty Coil Pack so only 2 cylinders were firing

Try the leads first tho

Replace leads First. Won't be the O2 sensor as it dose not come into play in the cold start .
An O2 sensor will only start to work after roughly 4mins this is how long the sensor
takes to warm up. the link between cold start problems and them being fixxed by the O2 sensor replacement dont ADD UP
And yes you can test a O2 sensor with a multimeter but you need one with the bar graph across the bottom . when the O2 sensor is reading Correctly the bar graph will run for side to side. Indicating the voltage variation from 1 - 1.5 volts ( or there abouts have to check Text books )
I hope this helps

I reckon leads. The give away will be that till run like a pig to about 3000 where it'll become a lot harder to tell that it's only running on 3.

Ohh and when mine did the leads as soon as it warmed up it ran alright.

i have a similar problem and was told by the mechanics that i need a new O2 sensor. he reckons it'll fix the problem. anyway, just passing on what i was told as i'm no expert, even tho it conflicts with what russellb said ...and he seems to know what he's talking about

Fatty wrote:i have a similar problem and was told by the mechanics that i need a new O2 sensor. he reckons it'll fix the problem. anyway, just passing on what i was told as i'm no expert, even tho it conflicts with what russellb said ...and he seems to know what he's talking about

Fatty, dont go get it just yet. the mechanic can tell you that, and as long as he says it confidently and convincingly, it'll seem like he know what he's talking about.

The easiest and cheapest way to test it is to get someone with the same model MX5 as you and put their leads into your car. If the problem persists, it's not the leads (unles theirs are stuffed too) and you can move onto other avenues. You haven't spent a cent on parts or labour either!

The easiest and cheapest way to test it is to get someone with the same model MX5 as you and put their leads into your car. If the problem persists, it's not the leads (unles theirs are stuffed too) and you can move onto other avenues.

And thats how the dealerships fix most problems. By replacing suspect parts with good ones. if that doesn't fix it they replace something else. All well and good if u have a spare parts car handy.

thanks guys

Just an FYI

I have this problem now. If i unplug the O2 sensor of a morning and start the car, it drives fine. If i cold-start it with the O2 sensor plugged in, it runs like crap.

I have already changed the plug leads and the plugs.

Make of that what you will.

phatMX wrote:Maybe because the O2 sensor is stuffed it IS sending a different signal when cold???

My point exactly

The initial poster never explained whether the problem went away at higher than idle RPM or once the engine warmed up to normal temps. A previous plug change helped initially so that's probably why most people are suggesting leads as the first thing to try.

There is insufficient information to assess/guess the actual problem.

Fixed yet

bit of an update, clean the MAF sensor, throttle body, change leads...... still got a mild idle drop upon hot/warm startup..... I have to rev it past 4k rpm and it goes away...... been reading on the forum and maita.net seems like it the coil pack is on the way out...... spoke to Daniel at mania he said the same thing......

The trouble is a brand new coil pack is about 600 bucks and i might consider the spitfire individual coils for about 900

Sorry to hear that