Hi guys, I'm new to the forum, And I would consider my self a pretty good technician (with 30 years of BRP Rotax technical development experience behind me)
But I am not very familiar with these Volvos
Lookin for help please! I have a 2008 C70 with 70,000miles on her. recently, after sitting for a month or two when I fired it up the engine started misfiring ALL 5 CYLS.
I replaced spark plugs (w Bosch Volvo Plugs) & cleaned & verified all coil wiring harness have grounds. cleared codes, engine starts runs smooth for a brief period of time while in park.
As soon as I drive she starts misfiring, Check engine flashing & throws the same 4 to 5 cyl misfire codes. NO OTHER CODES ARE PRESENT. no sensors out of range or failures...
I'm Baffled. I cant believe all 5 coils or injectors can go bad at once....
I Had it on a scanner fuel pressure appears good, fuel trim looks good always settles in around 1.
cant find any obvious Intake leaks, (blew smoke in intake, nothing obvious... checked for excessive crankcase pressure thinking maybe PCV issue, but it appears the same as my stepsons 2012 C70.
Any good Volvo techs out there who has experienced similar issues?
Recently I have been wondering, Can a bad Brake booster be the culprit? I replaced the master cylinder and all 4 corner brakes fairly recently & bled them multiple times now, yet the pedal still feels crappy...
Could it possibly need a new Brake Booster, or check valve???
As I mentioned, I'm a technician "not a mechanic" and I don't believe in just changing out parts to try to solve the problem with out understanding the root cause issue at hand!
Any Volvo Master techs out here? Please help...

 

Welcome to the forum

 

Unhook the brake booster from the intake manifold and see.

If it misfires on all 5 cylinders then fundamentally you have to be too rich or too lean, right? how else can that happen? I'm a fundamentalist so I'm satisfied with that.