My S60 has a rough idle. I installed a mass airflow sensor and still has rough idle. When I unplug the mas it gets better. It does still have an irattic idle. It also now has a slow response at first acceleration. What should I be checking for? I thought maybe the tps but I don't want to buy one unless some tells me to. Any ideas?

 

Your first step should be a scan with VIDA - the stolen/hacked software is free, a cloned chinese dice unit is ~$80

Or - randomly buy and replace parts hoping what you are doing will fix something -

Rough idle could be a misfiring cylinder - what codes are stored?

 

No codes appear although the check engine light is on.

 

If the check engine light is on - there are codes, just whatever you are using can't read them - VIDA can.

 

what device did you use to scan for codes? I'm pretty sure the 02s had moved to the CAN protocol but even my $29 Harbor Freight can read both CAN and ISO9141. Just make sure to plug your reader into the port with the key off, then turn the key to position 2 (dashlights on, engine off). You'll see it communicating and indicate if any codes have been found. unplugging the MAF would surely set a code so at least that one should be found.