temp gauge is fine, not sure exactly what it reads but all is normal. not sure what colour the coolant temp sensor is, if its on the water hose, its black.

car is cold just now and I am at work, I will check temp on the way home and post tomorrow morning

Gauge should go to 90 degrees when warm and not move at all until it is cold again. It would be worth asking your mechanic to plug in and check the gauge sender reading against what it is telling the ecu, the ecu side of the sensor may be causing problems.

 

By that I mean it could be showing 90 degrees on the gauge but telling the ecu it is reading 60 degrees, thereby making the ecu richen up the fuelling, have I explained that well enough?, as I struggle to explain things at times

yes I understand perfectly what you mean. have it booked into the garage next Wednesday for a pre MOT as its due in 6 weeks and I like to have time to fix things.

ok, reading thiis new info in this topic, is the exhaust blowing at all?

im going to make a wild guess and say this rev dropping thing happens at 2 second intervals right?

And I'm, as well as the above, wondering about collapsing PCV pipes, which need checking by hand since some are impossible to get a head more than 10mm diameter to the right place to look at, some cracks open and close, and if there are any externally fabric reinforced pipes they can collapse internally but look fine.

This just needs time to check.

might be dropping every 2 secs or so. why? what are you thinking.

 

temp gauge is reading a steady 90 when hot.

 

exhaust is not blowing at all. new cat last year, middle section about 6 months ago and a back box less than a month ago. not because it was blowing, the metal bar that connects to the rubber broke.

_{I think your right about the exhaust, there is a slight purr from the middle somewhere, I just checked.}

I'd put money on there being a leak up front before the cat somewhere, it's tricking the ecu into thinking it's running too lean by drawing air into the exhaust and over the oxygen probe, so the closed loop fueling is reacting on a 2 second cycle (which it should) but it still thinks it's lean so keeps pumping fuel in..

can you pull one if your spark plugs out and get a close up photo of it..

cant tonight, I am at work again.

 

I struggled a little bit last time I changed the plugs, kind of hard to get in at. took longer than expected.

 

will try tomorrow before I leave for work. will let you know either way.