I have another issue with my same Volvo specimen, a ’99 S70 non-turbo, equipped w/a manual transmission.
Background: On 7/2013 I changed spark plugs at 100K miles, used Volvo OEM plugs from FCP Groton. Meticulously followed the process using dielectric grease.
The issue: Fast forward sixteen months, add another 15K miles and the engine starts without any problems, at idle the engine runs fine at the expected ~900 RPM. However, while shifting when slowing down – e.g. just before making a turn or coming to a full stop – I notice a sharp drop on the RPM gage dropping to 300-500 levels and in a very few instances, the engine cuts off. My tendency is to shift into neutral when approaching to a red light and notice the same symptoms, and almost all the time, the RPM levels will remain in the 300-500 range showing hesitation before idling up to the normal RPM range. I also notice that if I press the clutch, the idle RPM will normalize immediately to the 900 range. I thought of a possible vacuum hose leak but can’t identify anything – probably I’m not looking at the right places.
Any idea??
Trouble shooting suggestions? 
Thanks!
alam
