I have a 2002 Hi Pressure Turbo motor. THe car runs fine for 90% of the time but at idle it gets an intermittent misfire. When it idles good, its smooth as can be, when it misses its only one cylinders worth of miss. I have done the following:
New VOlvo Plugs
New Bosch Ignition Coils
Swapped around Injectors
Cleaned throttle body
When I had the motor out, I cleaned the PVC system, pulled the pan and cleaned it out and the PVC passages. New belt etc. All new motor mounts...

I have isolated it to the number 1 injector. If it is missing and I Pull the #1 injector plug when it is misfiring, the misfire doesn't change, all the others do change. I have swapped around injectors till I was blue in the face as they say, I have an entire second motor's worth of injectors, made sure they were the same s/n as the ones on the installed motor, I am convinced it is not an injector plus I cleaned them with my home made cleaner.

Background, I pulled the motor out of a T5 when my old one overheated and roached. the car has 165k, the motor 110 k. I replaced the vacuum hoses and have retraced them a thousand times making sure the one-way valves were oriented correctly. Couple of I believe non-related issues:

Twice in the last month I started the car and got a ECT light and the throttle did not work. I restarted a couple of times and it has been fine each time. Eventually the light goes away.
If I floor it, the car takes off like a scalded rabbit, if I give it 1/2 or to 3/4 throttle it missfires, not just one cylinder it really misfires till I floor it. First half of the throttle works fine.
I think both these problems are likely related to the ECT needing an update to magnetic but not sure.

I love this car its actually a 1gen C70 but I post here due to the sheer volume of viewers and its specific to this era car which has its own idiosyncrasies e.g. ETC. I have wrestled with these problems for 2 years and have posted before likely. It is my daily driver and runs great, I invested in it to keep it for 10 years e.g. all new motor mounts etc. Would love to solve this idle issue...

Best regards, Mark

 

I'd look at (replace) the throttle - Your c70 has the Magnetti mareilli (sp) throttle module - has it be replaced? I'm guessing that's related to your "ECT update to magnetic" comment.

If you have VIDA or a compatible scan tool you can test/monitor the throttle module operation.

 

It has the white label ECT and it has not been replaced. I am living in a motorhome while I purchase a new home. As soon as I have a garage, I will convert the ECT. I will run the car by the local volvo whisperer and have him vida the system - good idea...