Engine cutting out and not wanting to restart

[mikejevans]

Hello,

A while back I noticed that the temp gauge on my dash wasn't staying in the middle, it would occasionally drop down (sometimes to the bottom, sometimes to about a quarter) then suddenly shoot back up to the right temperature. A little while after this the engine warning light came on. diagnostics said it was the 1st lambda that was causing the light to come on.
it went away for a little while but then came back. Also when under heavy acceleration if the temp dropped suddenly the the engine would also cut power but be fine if you lifted off and kept it at a constant speed.

I have replaced the thermostat after being told that it could be jamming open, causing the engine to overcool and that could be causing an odd oxygen reading on lambda sensor (got a little lost at this point, but I'm assuming the ECU puts different amounts of fuel in according to engine temp?)

This did not fix the problem, other problems are that the car has a very erratic idle (sometimes 750rpm, sometimes high as 2000 and everything between) also it is now cutting out at lights and roundabouts, and not restarting straight away. lastly the fan is now staying on after i turn off the engine, which it never used to do.
now the next part may be my imagination, but it seems the problem is worse when the car is pointing up hill. Both times it cut out today it would not start again for ages, but when i rolled it back down hill to level ground it the started. This could just be due to leaving it for the time it took me to roll it down hill, but it seems odd it only ever cuts out when pointing up hill.

I've had a look on here and found lots of similar issues, but none seemed to have the same symptoms as mine. The only thing i can think that's left is to change the water temp sensor, but I don't see how this will fix all the problems unless the temperature reading is causing the ECU to do all sorts of odd things.
I was just wondering it anyone has any advice before i take it to Renault and pay stupid money to have a cheap part replaced, any help would be appreciated!

Cheers

 

[Mickey77]

Coolant Temp Seensor can cause rough running issues and the cutting out could be a gash throttle body, the starting probs could be TDC Sensor.

Best thing is a diagnostics, as its all speculation at this point.

 

[mikejevans]

cheers, when faults first started diagnostics said the only problem was the 1st lambda but that was when problems weren't so severe. Got a new coolant temp sensor coming tomorrow, so will clean up the TDC sensor while i have airbox out as I've seen a few posts about it on here.
Will problems with the throttle body be noticeable if I were to have a look at it tommorrow? I checked if it needed a clean when I replaced the stat the other day and it seemed fine, but I didn't have a proper look at it. Any recommendations on what to look for or are problems not going to be visible?

 

[Mickey77]

Was the diagnostic machine a CLiP or a generic OBDII? CLiP can pick up on things OBD wont. Best to get a proper diag done rather than tossing money at the car

 

[mikejevans]

No idea if i'm honest, was over at BTM getting an exhaust fitted, mentioned the problem and he plugged it in and showed me the faults. I put the new coolant temp sensor in today and so far it seems to be running fine. completely agree about not throwing money at it but part was only £17. If the problem comes back I will get someone to have a proper look at it and not just keep on guessing and wasting money.

I will let you know what happens in a week or so for the benefit of anyone else searching the site with similar problems.

 

[mikejevans]

Quick update for anyone searching with similar issues:

coolant temp sensor was replaced about two weeks ago, and it now runs fine. I've since found out that if the ECU thinks the engine is cold it will run rich. This would cause the fault reading on lambda sensor, and cause the engine to cut out and not want to start when the engine is up to temp.