Struggling to run when cold
Discussion
After some advice...
I have a 2006 saab 9-3 2.8T V6 and it seems to misfire badly but only when cold.
I've changed the spark plugs but it didn't help.
Now it's getting cold it's actually struggling to stay running for the first few minutes, but then runs fine.
My thoughts are coil packs or the ecu, as they are both known to fail due to high engine bay temps, but no idea why they would only do it when cold. I'll give swapping them a go, but just wanted some other opinions first as they aren't cheap.
I have a 2006 saab 9-3 2.8T V6 and it seems to misfire badly but only when cold.
I've changed the spark plugs but it didn't help.
Now it's getting cold it's actually struggling to stay running for the first few minutes, but then runs fine.
My thoughts are coil packs or the ecu, as they are both known to fail due to high engine bay temps, but no idea why they would only do it when cold. I'll give swapping them a go, but just wanted some other opinions first as they aren't cheap.
paintman said:
Diagnostic?
Probably cheaper than firing the parts cannon at it.
There isn't anyone with a tech2 around here, which is the only thing you can use. I've got a Bluetooth obd2 scanner but it doesn't find anything. Probably cheaper than firing the parts cannon at it.
The nearest diagnostic is Nottingham Saab, but it's a 45 min drive each way and I'll struggle for time to do that at the moment.
catman said:
Could just be a faulty temperature sensor.
That makes some sense.I actually have one of those to fit somewhere!
I started, then realised it needed a lot more removing than I had time for as it's behind all of the intercooler hoses and fans.
Might try to fit that once this damn cold has gone, thanks.
Zener said:
I presume this is fitted with hyd valve lash/clearence adjustment 
are you using the correct viscosity oil?
It had had an oil change when I got it in May, but I assume so. are you using the correct viscosity oil? I assume its got hydraulic lash adjustment.
It doesn't use any oil at all as I did wonder about engine wear as it's on 151k
james6546 said:
There isn't anyone with a tech2 around here, which is the only thing you can use. I've got a Bluetooth obd2 scanner but it doesn't find anything.
The nearest diagnostic is Nottingham Saab, but it's a 45 min drive each way and I'll struggle for time to do that at the moment.
Absolutely incorrect there my friend. Most half decent scanners or diagnostic tools will read your car. Even my old original Launch x431 can read all the systems on these cars. Snap-on, Maxidas, Opcom, Delphi, Bosch and so on which most garages will have at least one of. The nearest diagnostic is Nottingham Saab, but it's a 45 min drive each way and I'll struggle for time to do that at the moment.
If the coolant temperature sensor is faulty the ECU may be getting a signal that says the water temperature is, say, 80c. That will cause under-fuelling i.e. too lean.
N7GTX said:
Absolutely incorrect there my friend. Most half decent scanners or diagnostic tools will read your car. Even my old original Launch x431 can read all the systems on these cars. Snap-on, Maxidas, Opcom, Delphi, Bosch and so on which most garages will have at least one of.
If the coolant temperature sensor is faulty the ECU may be getting a signal that says the water temperature is, say, 80c. That will cause under-fuelling i.e. too lean.
Thanks, that's good to know.If the coolant temperature sensor is faulty the ECU may be getting a signal that says the water temperature is, say, 80c. That will cause under-fuelling i.e. too lean.
To be honest I've not looked at it as we have had some bad family news so we are staying with my mum for a while. I've just been stealing her garage.
I'll change the temp sensor at some point as I've got one and go from there
With no diagnostics, temp sender is the cheapest place to start, as well as a likely culprit.
I had an old Saab 900 that did exactly what you describe. New temp sender fixed the problem. It was easy to change, unlike yours, so I thought I'd give it a go before paying for any garage time.
I had an old Saab 900 that did exactly what you describe. New temp sender fixed the problem. It was easy to change, unlike yours, so I thought I'd give it a go before paying for any garage time.
LordLoveLength said:
Can’t you just unplug the temp sensor and plug the new one in to test? It doesn’t need to be installed to check cold running and from your symptom description it just needs to be run for a couple of minutes to confirm.
That's a really good idea. I'll grab the sensor when I go homeUpdate to this post. It's still running really badly when cold, now it won't really accelerate for a while and yesterday backfired when I started moving. It's still fine when warm.
It's had a new coolant temp sensor, spark plugs and fuel filter.
I can only think of two potential causes, either the secondary air pump system, which is making the car run too rich as it's not working or the valves aren't sealing properly. Neither is cheap to sort on a shed.
Any suggestions on what else I can try? I don't think it's a coil pack as it's only when the car is cold
It's had a new coolant temp sensor, spark plugs and fuel filter.
I can only think of two potential causes, either the secondary air pump system, which is making the car run too rich as it's not working or the valves aren't sealing properly. Neither is cheap to sort on a shed.
Any suggestions on what else I can try? I don't think it's a coil pack as it's only when the car is cold
steveo3002 said:
is the temp sender giving out correct readings ...not unknown to get bad ones
and is the temp sender wiring intact all the way to the ecu ? assume code reader can show what coolant temp is
Good idea, I'll connect my cheapo odb connector and see if it shows anything.and is the temp sender wiring intact all the way to the ecu ? assume code reader can show what coolant temp is
I don't ever get any engine warning lights.
Weirdly it seems to be getting worse, it used to just be in cold weather
As above post, check the live reading of the temp sender and ensure its not reading 80c+ when stone cold.
The secondary air pump is easily checked. Its just a motor with 2 wires and an impeller so connect it directly to a power source (car battery will do) and it should spin. If it does not spin you can easily dismantle it - assuming you have some basic tools and some mechanical skill - clean it up as the impeller is most likely seized rather than the motor burnt out and it should work again.
Failing that there is one for sale for £46: https://www.ebay.co.uk/itm/144681418962?chn=ps&...
The secondary air pump is easily checked. Its just a motor with 2 wires and an impeller so connect it directly to a power source (car battery will do) and it should spin. If it does not spin you can easily dismantle it - assuming you have some basic tools and some mechanical skill - clean it up as the impeller is most likely seized rather than the motor burnt out and it should work again.
Failing that there is one for sale for £46: https://www.ebay.co.uk/itm/144681418962?chn=ps&...
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