Weird Idle On My 1984 Volvo 242

My 1984 242 has developed a strange idle. It currently has 199,000 miles
and last had plugs and rotor cap replaced a few thousand miles ago.

The engine speed at idle is speeding up and slowing down and sort of
"surging". This has begun in the last thousand miles. It also has a
tendency to die when initially started and than stay running the second
time. This occurs when the engine is cold or warmed up and running for
several hours. One other thing is that it begun pinging badly and has
been getting worse. Is this a timing issue or a timing chain issue? I
have had the car for 3 years and 65,000 miles and these problem have
just cropped up recently. Any help or suggestions would be much appreciated.

The car does run fine at freeway speeds.

Thanks,

Dave

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Rectify the intake vacuum leaks. If that doesn't cure the idle and
pinging problems, make sure that the radiator is clear, the coolant is
clean and that the O2 sensor hasn't been damaged from running the motor
lean all the time.

Bob

 

I would also check the wiring harness. If I am not mistaken, this is
one of the years (1982-1987) Volvo used that stupid biodegradable
wiring harness. My 1988 780 gave me fits with hard starting when warm,
idle surging until I replaced mine. Once I replaced it, it was like a
different car.

 

It never hurts to clean the throttle body.

 

Just got done fixing surging on an 83.
Did the following in this order.

Fixed wires inside harness. Removed intake to do and just unwrapped bundle,
spliced in new one at a time, rewrapped bundle.

Replaced Hall sensor in distributor which smoothed things out considerably.

Replaced the coil, it became too hot to touch after about five minutes of
running that it just seemed like a smart thing to do.

The temp sensor for the ECU since it was getting really bad gas milage and
the plugs were carbon fouled and wet.

Your situation may vary, except maybe for the Hall sensor, IMOP.

Duane

 

A vacuum leak will also cause this sort of problem, but yes replace the
wiring harness too if this hasn't been done. Personally I would replace
*all* the vacuum lines under the hood just as a preventative thing,
it'll cost maybe 10 bucks for the hose.