1987 volvo 244 DL idles fine, stutters and backfires at highwaycruise speed

Symptoms as described above: At idle, the car sounds and behaves fine.
No problem starting. However yesterday at highway cruise, momentary
loss of power occured at irregular intervals, accompanied by
occasional backfires.Power loss duration was from split second to up
to 20 sec.
About 2 weeks back, the Smog check mechanic stated that the hoses to
the evaporation canister are cracking. He also adjusted the timing by
several degrees, making what I thought to be an occasionally rough
idle.
4 yrs ago, I replaced the failed original air mass meter.

Could the problems described above be from the evaporation canister
hoses being more severely cracked? What is the function of the evap
canister during highway-speed cruising?

My first suspicions are for air mass meter, but the fact that cracked
hoses exist on the evap canister make me want to understand that
system better.
Any help appreciated!

 

IT STUTTERS BECAUSE YOU PUT THE STEERING WHEEL ON THE LEFT SIDE WHERE AS IT
SHOULD BE ON THE RIGHT .Clean every thing including the idling motor control
thingo it get gummed up .Its under the intake manifold with simple
electrical connections and hoses coming out of it .I swirl cleaning fluid in
it and make sure its free of grit .Its is like a motor inside but only turns
a bit to allow air correction .Hoses are a must cheap and simple the
evaporator cleans the hydro carbons out of the air back into the mixture
rather than vent them out side .My Volvo is 12 degrees before top dead
centre ,which is correct .Maybe your is different but make sure hes not far
from the mark as it ruins the preformance .

 

Has the outside of the harmonic balancer spun on the rubber damper? That
can make the timing way off when the mark shows it to be just right.

'87 is also one of the years with the biodegradable engine wiring
harness, I've had to replace several of those, the car will never be
dependable with the original harness, the insulation crumbles all over.
I rebuilt a few by splicing in all new wires from near the firewall to
all the connectors since the cars broke down.

 

Thank you for the input; I'll check the timing again, perhaps with a
better mechanic than I am. Also tonight in a more diligent inspection
of the engine, I found the hose between the evap canister and the
intake manifold was completely severed. Bought a new length, and will
install it shortly.
The idling motor control you mention: do I need to remove it to clean
it, or can it be cleaned in-situ?

 

Thank you for the hints! I'll check the wiring for cracks.
How would I tell if the harmonic balancer has spun? Is there another
reference for comparison? Not too familiar with this one...

 

Here ...

http://www.swedishbricks.net/700900FAQ/Engine-Mechanical1.html#Failure_of_Harmonic_Balancer

 

Yeah definitely replace any cracked hoses, those aren't helping anything.

You might be able to clean the IAC valve in place but you'll save
yourself time and headaches by removing it, there's only two bolts to
loosen, a couple of hose clamps and an electrical connector.

 

You can set the engine to TDC by looking at the mark on the cam pulley
which you can see if you remove the screw at the top of the timing belt
cover and pull the cover away a bit. With it lined up with the mark on
the backing plate the mark on the crank pulley should line up with the 0
mark on the lower cover.