1984 Plymouth Reliant (2.6L) still idles way too fast...

I got my hands on the Chrysler FSM. Can't say as it has helped me all that
much. Vehicle in question is a 1984 Plymouth Reliant with the Mitsubishi
2.6L engine. As best I can tell (although the pictures in the FSM still
don't quite match), the car is equipped with the "feedback" type Mikuni
carburetor. There is a throttle position sensor on the carb, which the
non-feedback type does not seem to have. Fresh fuel helped somewhat with the
dieseling, but when fully warmed up, it will still diesel when shut off.

Connecting a tachometer to the engine shows it idling around 2000 RPM.

Sometimes the car will start and idle nicely for a brief period of time,
maybe a few seconds. Then it throttles up and takes off.

I'm running thin on ideas. Can anyone help? Thanks in advance for *any*
answers, suggestions, thoughts, etc...

William

 

I just had a similar problem earlier today with the same year and make
of car. From what I have been told, one of the vacuum lines is loose
or disconnected and the car is sucking way too much air. I have not
found the idle screw but will report where it is late tonight. Would
you know where to find the vacuum line diagram?

Rob

 

Hi!

The one in my car is printed underhood, where the hood meets up near the
windshield. If yours is gone, I could try photographing mine and posting a
link. There's also a diagram in the FSM that I might be able to scan. (My
scanner is somewhat precariously balanced and might not stand having a
Chrysler FSM thrown upon it...!)

Something else to check--make sure the secondary on the carb is *not* stuck
open. If it is, you'll have a racing engine. I freed it up and now
everything works...properly. The idle adjustment is now both possible and
effective. The car drives a lot better too. (Yeah, I know...that sounds like
a "well, duh!" thing to say, but...). I have noticed something of a "flat
spot" when getting up to speed, but I really don't care to look into it.

William

 

These Minuki carbs were notorious for being hard to adjust. Some of
the adjustment screws were covered, to prevent tampering. It seems
like Holley or one of those offered a replacement, but I can't
remember for sure.

-KM

 

Hi!

I see some of the covered screws ("tamper resistant idle mixture screw") in
the FSM. Fortunately, it seems like the adjustments are pretty much correct.
I've found and fixed the following problems:

Stuck choke (stayed open or closed all the time)
Stuck secondary barrel damper (now opens and closes like it should)

The car now runs correctly, idles down as it should and seems to be doing
well. Yesterday it acted like it was going to run out of fuel if I so much
as dared to touch the gas pedal and it wouldn't idle properly. So I pulled
the fuel filter and drained it to find that there was a bunch of trash in
there. The Autozone-branded replacement wouldn't flow fuel at all (it seemed
to have something causing total blockage), so I fashioned a straw to join
the two hoses and went for a brief test drive. Performance was much better
and fuel flow was clean and even. I'll get a better filter.

Every problem I've run into so far has been result of something being stuck,
dried out, rusty or all of the above.

In other words, I think that I've just about got it.

William

 

I worked on a Corolla one time that had a major dieseling problem on
shut off. Actually, it would *never* shut off unless you put your
hand over the carb and choked it out. The problem turned out to be
a faulty vacuum advance (or retard) mechanism in the distributor.