Hot start misfire

Ok this one has me stumped completely, and before I start just changing parts willy nilly just wanted to see if anyone can offer any pearls of wisdom.

From cold the car starts fine, drives fine, all is normal as far as I can tell, but If I get the car warmed up and then stop it for a short while, to go into a shop for example, then often when I come back to the car it will badly misfire and will not clear with revs, I have to turn it off and on again, often multiple times, until it starts normally, at which point all is fine and it drives fine, It is progressively getting worse.

A bit of throttle when it's misfiring and it stinks of fuel with associated vapour from exhaust so it kind of seems like it's creating a flooding condition but I don't understand why?

I suspected perhaps ECU coolant sensor but it seems to be reporting fine to Nistune unless intermittent. Put new plugs in today as was doing oil and fiter anyway. I have a new dizzy cap, rotor arm and coil there but not sure if it's ignition component related. cold idle valve always open perhaps? There are no fault codes.

Any ideas or anyone experienced this?

Cheers.

Sounds a strange one .... if it goes ok after a few turn on and off's like your resetting something ....

No idea nomad, totally stumped.

Was suggested to me that maybe an injector was leaking, Pulled the fuel rail off today and pressurised the system, no leaks at all when hot or cold so that rules that out.

As it sods law I couldn't get the car to misbehave today to try and narrow down which cylinder is misfiring.

If it dose it whip a plug see which one is fueled up ?

That was the plan but couldn't coax it into misbehaving today.

Perhaps a fault code check when it's hot may point you in the right direction?

Unless as you say it's intermitant  and a injector sticking or something

Thermal wrote:Perhaps a fault code check when it's hot may point you in the right direction?

55 every time.

johnny gtir wrote:Unless as you say it's intermitant  and a injector sticking or something

I would think a sticky injector, even intermittent, would also cause misfire when driving and on cold start too. Fuel is being thrown out the exhaust when its doing it so I'm confident it's not a fuel supply issue.

Is your lambda sensor plugged in ? When I took mine for an mot he saw underneath someone had cable tied it back instead of plugging it back in? Just a thought buddy

Plugged in and reporting to nistune

Still haven't tracked down the issue here, always happens at the most inappropriate times, like the night before my wedding so had to swap cars just in case!

Changed coolant sensor which did seem to solve the problem temporarily but it eventually came back worse than ever, causing the EML to flash while driving and lumpy running, the next cold start and everything was fine again and drove over 20 miles without a problem, tried to restart it out of curiosity and was misfiring.

No error codes even when the EML was flashing.

That was 3 weeks ago, took it out today and was fine, hot restart, no problem, changed the coil as had one there but I doubt its the problem.

So have done a lot of tinkering with this, having changed a few bits like ecu temp sensor and some ignition parts without success, all sensors are functioning as normal according to nistune.

I have discovered that is is not a ignition related misfire but rather it overfuels to the point where it misfires and stumbles, I pulled the plugs after an episode and all were fouled with soot, backed up by the amount of fuel coming out the exhaust, cleaned them and it fired up first time no problem.

I noticed the other day that sometimes when I turn the ignition on the radiator fans come on too, at the time I didn't think much of it but today I noticed that the only time it misbehaved was when the fans had come on, the many other times I had tried to start it today had been a success, unfortunately it stumbled and stalled on that occasion rather than maintaining a rough idle. Not such what link there would be there but there does seem to be one.

With that in mind I did the active fan tests and maybe 2 out of the 10 times I ran the test I would get a "check pin failed on this board" error and it would disconnect, I don't know what that means, anybody offer some insight, could I have a intermittent fault with the nistune board?