Rough running for few minutes after cold start

giovannibianco · Post by **giovannibianco** » 19 Jan 2021, 12:15

Hello Everyone,

Another problem, or rather an annoyance, has arisen with our 1997 V70. In the cold mornings: the
motor starts fine; runs for few seconds; then starts running slowly chugging and spluttering; after
maybe 3-4 minutes the chugging goes away and she runs smoothly afterwards.

During the chugging phase, it is not possible to drive... no power. So something warms up and delivers a good signal
to the ECU? If I was looking at one of my older carburetted cars I would be looking at the choke operation...

I have also made a test after car has sat for 6h in covered (not heated) underground parking and the problem did not happen
so it's a temperature-related effect. Tomorrow morning I will log the OBD-II data during this period.

Any ideas?

Cheers, John.

1997 Volvo V70 GLT B5254S motor 415,000 km.

Post by **Chuck W** » 19 Jan 2021, 17:55

Check your ECT(Coolant Temp) sensor and its connector. Corrosion on the connector can cause a bad signal.

Post by **scot850** » 20 Jan 2021, 19:39

+1 on checking the ECT sensor.

Neil.

giovannibianco · Post by **giovannibianco** » 05 Feb 2021, 06:52

Hello Everyone,

Thanks for the replies... sorry for delayed response. I checked the connection to the temp sensor... looked good. A bit of wiggling while doing this revealed that the "sonde" was actually loose inside the temp sensor. What I'm trying to say is that the temperature sensor has come apart internally. I can pull the internal bit outta the threaded housing. As this cannot be optimal for things, I have ordered two replacements. One for the motor and one for the tin of "bits that will get this car going again" that lives with the spare tyre. New parts arrived yesterday and install/test over the weekend.

Cheers, John.

Post by **Chuck W** » 05 Feb 2021, 17:33

Sounds like you may have found your issue.