idle control motor failure 240

My idle control motor on my 83 b21ft doesn't seem to be doing much of
anything, i can unplug it and the tps and the thing runs about the
same (generally OK, just a slow idle when cold). All the wires are
new and I cleaned it out (was oily).

My question is, when in the normal failure mode, will this non working
idle motor be a possible cause of my lousy (about 17 mpg with a new
cat converter) fuel ecomomy or produce rich running?


I don't feel liek replacing this $100 part right now, but will do it
if it is causing damage, especially to my new converter. Any wisdom
is most helpful.

 

The idle motor only controls the amount of air bypassing the closed
throttle. Thus the only thing it affects is idle speed, it won't have
any effect on mileage, or your new cat. The failure mode depends on the
position of the valve inside the motor. If the valve is closed, then
you'll have symptoms such as you mention. It could fail open, in which
case you'll have OK idle when cold, but a high idle when warmed up.
Often they are gunked up, preventing them from working correctly, but
sometimes the motor is just burned out, so cleaning won't help. Make
sure that your throttle switch is adjusted so it clicks when
transitioning to and from the idle stop.

When I suddenly had poor mileage on my '83 240 Turbo, I first tried the
normal tune up stuff, which didn't help at all. Then I determined that
the oxygen sensor wasn't working - an new one fixed the mileage back up
to where it had been. This is what will hurt the mileage and the cat.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Oops, I just bought a new one today. I think I understand now that
the idle system and the fuel injection are two distinct systems. Am I
asking too much to expect this 245 turbo to get 20 miles to US gallon?
(I did do the tune up stuff and 02 sensor already). Maybe I have a
leaking injector or somesuch. I could be driving a big caddy or a 1
ton truck if I wanted to get 15 mpg...

 

I normally got about 425 km per 50+ litres on my 245 Turbo (manual
trans). This works out to 19-20 mpg (US gallon). With a dead oxygen
sensor the distance was only 300 km (14 US mpg). With my 1998 V70 T5,
(auto trans) the same type of driving usually nets me 10 litres per 100
km, about 23-24 US mpg.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

My dad has a 245T with an automatic, he said it gets about 25 mpg on the
highway, not sure about around town. I have a 242T and get similar mileage
with a manual, but I probably drive it a bit harder.