Hi Paul - I have two 1989's with the same engine. My 2wd isnt running
right now but when it did - it did the same thing. My 4x4 also does the
same thing. I really only notice it when I have it in park or neutral
and I am warming up. I have been able to hold the truck at a steady
idlt of 1K RPM - but around 1200 - 1500 no matter how I modulate the
throttle it goes up and down up and down about 100 RPM's. 1800 RPM and
above - no problems.
THis could be related to a bad IAC motor. Idle Air Control... Its the
gadget with the plundger mounted on the drivers side if the TBI. Its an
electric solenoid/motor that sets the butterfly position when the engine
is off - so it starts properly - and it also helps maintain idle (hence
its name)
That could be dirty or malfunctioning.
I would also double check the obvious stuff, plugs, wires, cap, rotor.
Might want to run some fuel injector cleaner through the gas tank.
Also check PVC valve and the hose. Check throttlebody vaccume ports.
There is a little vacume line plate held on with three torqux screws on
the front of the Holly TBI. That plate comes off and can get pretty
gunky. YOu might want to take the TBI off and take the whole thing and
give it a good cleaning.
I have not given it a 2nd thought and I just drive my truck the way it
is. Considering its on its last leg and could conk out on me any day...
poor idle is the least of my worries LOL
Rapom66@localnet.com wrote:
> Hi DML, I just signed up in the hope that one of you could help out a fellow
> Mopar enthusiast down on his luck.....
> I have a 91 Dakota, 2wd, ext cab, 3.9 Throttle body EFI that does not want
> to run smoothly just off idle up to about 1400 rpm. This is most noticeable
> under slow acceleration or unloaded (neutral) If you accelerate rapidly you
> do not even notice the problem. Once you get past 1400-1500 rpm the motor
> smoothes right out and runs excellent. The problem seems worse during cold
> weather. In addition to this my fuel economy is off by 3-4 mpg.
> The motor is orig. with 140K on the clock. I replaced the timing chain &
> gears at 110K, I recently replaced the coolant temp sensor and throttle
> position sensor neither of which seemed to help. The EGR valve is in good
> shape, not plugged and appears to be functioning corectly. The truck
> received a full tune up 4 months ago (everything) including O2 sensor. I
> have searched & searched for vacuum leaks but have found none. I checked the
> computer using the key & check engine light method and it is not holding any
> codes.
> I am stumped.... I have been rebuilding old Mopars for 25 years and have
> never yet paid anyone to fix on one of my vehicles. I refuse to let this be
> the first one...
> Any advice you can offer would be greatly appreciated.
> Thanks, Paul S.
>
>
------------------------------------------------------------------------------------------ Terrible Tom
"It's a living thing... It breathes, it eats, ...and it hates..."
Silver '89 Reg Cab, V6, Auto, 8 footer, 4x2 Silver '89 Reg Cab, V6, Auto, 8 footer, 4x4 w plow - (aka Granpa)
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