Astra G dodgy temp gauge & o2 sensor issue

JustAnotherSaver

2 things i've noticed recently.


There'll be times i'm driving along & the temp gauge is rock bottom when it shouldn't be. I'll look down later on & it'll shoot to half way in an instant.
Monday for example i was on a 7 mile drive. It started getting to temp as normal & next minute i looked down it had gone from 1/4 to rock bottom. It stayed there until i got to just about the end of the journey which is when it shot to 1/2 way.


The thermostat was renewed with a genuine GM part last year.







Second thing is obviously when you're in too high a gear and the revs have dropped off you start juddering. It's not that. When in that situation my car now starts coughing & spluttering different to the usual judder.

I plugged in the diagnostics and it threw back this...





So i recorded the readings. This was with the car running after i'd just driven 7 mile, stopped for 10-15 mins & then done another 3-4 mile (& then took this reading)...





any of that stand out to anyone fluent in it?


I've cleared the fault so we'll see if the code returns.



Where's the sensor located anyway as i believe there's 2 o2 sensors? If this on the exhaust or manifold?


And any of you any clue about the temp gauge?

marlot

JustAnotherSaver wrote: »

...There'll be times i'm driving along & the temp gauge is rock bottom when it shouldn't be. I'll look down later on & it'll shoot to half way in an instant.
Monday for example i was on a 7 mile drive. It started getting to temp as normal & next minute i looked down it had gone from 1/4 to rock bottom. It stayed there until i got to just about the end of the journey which is when it shot to 1/2 way....

It could be that you have an air lock in the coolant system.

shaun_from_Africa

Regarding the temperature. I would say that it's either a faulty gauge or sensor, or more likely, a dodgy connection.
If it was the thermostat or an air lock, I would expect to see the indication to stay in one place then rise or fall gradually where as if the wiring was intermittent, a near instant jump between minimum and the correct indication would happen.

JustAnotherSaver

Why would this fault occur around 12 months after the thermostat was replaced?

IIRC the sensor is actually inside the thermostat itself, it all comes as one unit i'm fairly sure.

edde

Coolent temp seems fine on the readout but since it's not constantly wrong it's difficult to be sure of a fix, it could well be the replacement part is of poor quality and failed. Its not that uncommon for the cheap copied parts to fail. Copied parts often have original labels etc and bought via eBay etc.


Have you changed the coolent at any point?

The sensor your asking about is post the cat ie the one nearer the back of the car. Easy enough to change but it's behaving itself at the moment based on the readings you have added.

cassTL

instrument clusters are a weak point on the astra G.

JustAnotherSaver

Regards the thermostat itself (& the sensor since it's part of the same unit) - it's official GM. Not a no-name one. Anything with sensors i buy the genuine stuff due to poor experiences in the past.


I had the coolant changed last year also, same time as the 'stat.




And i hear you on the instrument cluster. My fuel gauge is all out of whack. It's mostly right but some times it'll read like i need to fill up when i know i have 1/4 tank left. It's worse in winter than summer. I actually use the miles display as a fuel gauge now. I fill up each time and know i get about 380-400 to a tank so when i start hitting around 380 i know it's time to fill up.