Strange engine behaviour on MK3 GTi 16v

[gavin]

Hi

Firstly, I'm new to posting on here so really sorry if I'm posting this in the wrong area!

I have a VW GOLF MK3 GTI 16v 2.0L

It starts perfectly and usually runs without an issue. However the last couple of months I've had two strange experiences. Second just happened today.
I went for a drive from Cambridge to Norfolk today (about 90 miles) and the car went like a dream... coming back, it started fine, and was again running perfectly.. but after about 20miles into the journey.. I got stuck behind a tractor so was going pretty slow, again no problem... then I pulled up at the lights and noticed the revs jump from idle to 2000 rpm, then slowly drop.... pulled away then noticed it started running rough... pulled over and could feel the engine running really rough, and smelt petrol... so it's almost as if the coke kicked in which I guess is why the revs picked up at the lights.
It was practically impossible to drive as the car was kangarooing and was difficult to keep the revs up..., engine at one point went to about 300 rpm on tick-over.. had to turn it off then start it again to get the revs back up a bit.... again the car started fine... managed to get on the highway and got the car running to 70mph.... and it was running smooth... got back and the engine is idling perfectly again... and petrol smell is gone.
So, any ideas... I'm thinking one of the sensors malfunctioned... but not sure. Have a cheapy fault code reader and read the codes on the engine and it said 0 errors....

Could it be the coolant sensor ? but dashboard gauge always read normal?
Or could it be the cat/lamda sensor?

Any help greatly appreciated.

All the time the temp gauge  read normal

[itavaltalainen]

Temp gauge reading normal doesn't bother the engine because it's a different temp sender (despite in same package) as the one for the dash.
Smelling of petrol to me would suggest a leak somewhere, or did smell come from exhaust?

Check the temp sender with a multimeter (I have posted a guide on here about 10 times).

[gavin]

Thanks.... yes smell came from exhaust..
Didn't realise gauge got it's reading from a different sensor.

Will try and check the sensor from your post

[Len]

What was the other strange experience?

[Khare]

My advice is to get the car on vagcom and check for faults there. It sounds like either a bad earth somewhere or a bad sensor.

[VW BUSH]

Coil is my guess but scan it first

[weazgti]

Check coil in the dark and see if its sparking on the outside of its housing and wiggle relay 30 when it does it or pull it out then push it back in whilst running.