Hi,

240 Volvo w/ 155,000 miles. Idles a tad rough but smooths out when you accelerate. You can go to the back of the car and it sounds like it has a small misfire.

Took off and cleaned throttle body, new plugs, wires, cap and button. Replaced all 4 injectors w/ upgraded 4 hole Bosh. Also found a broken motor mount so replaced mounts as well as tranny mount and removed and clean the air mass flow sensor as well.I also checked signal going to injectors with a noid lite and all seems good but....I can pull off the injectors wires and get a response from engine idle all all three except the front one. I pulled the wire off the air mass and engine runs rough and then gets better when I hook it back up. Idle surges up and then goes back down to the rough idle. Any ideas from here would be most appreciated...

 

How about that front injector? If you get no response from the engine when you unplug it, then that's your issue to investigate furrther.

 

I replaced all the injectors 3 days ago...I also checked the signal w/ a noid light and get a pulse to the injector. Got spark at number 1 as well.

Yesterday I searched for vacuum leaks by spraying starting fluid around hoses, manifold ect. Found a spot right on the top front of the intake manifold when i sprayed the RPMS reved up. So I suspect a failed gasket is the problem?