Idling issue - Any Advice?

[Rian]

Hi Everyone!
So glad to find this site. Recently purchased a 1988 Ranger with 84k original miles on it. A problem which has gotten worse in the last few weeks is the idling. When I am driving and come to a stop, it just wont stay idling. But it drives fine. I ordered an MAP sensor. Am I on the right track?!
Any input or help is much appreciated. Great site here! Love the ranger!

 

[Dirtman]

Test the IAC valve (Idle air control). They can fail, or become clogged up. Pull it off and see how much crud is inside it, clean it out, and test that the plunger opens and closes fully. If not replace it, only use a MOTORCRAFT valve!

 

[Rian]

Dirtman! to the rescue! Thanks so much for the quick reply and advice. I'm heading out to check on the IAC this afternoon in the cold. This is such a cool truck. I'll circle back and let you know how it works out.

 

[JohnG]

I’m new to the TRS so hesitate posting but read a ton. I would “pull codes”. Really easy and might give you a little more direction to what the problem is. It can be done with a paperclip and a test light or Volt Ohm meter.
There are many videos that teach how. Here is one:

I’m not sure about 88 but my 86 does NOT have a dash light so I have to use a test light.

 

[RonD]

Welcome to TRS

Its a fuel injected engine so will use an IAC(idle air control) Valve to set RPMs at idle
Engine Computer(PCM) controls the IAC Valve
On cold start idle should be high, 1,000 RPMs or so, the colder the temp the higher the idle
After a few minutes of warm up idle should be down to about 750rpms, manual trans can be 650rpms

If your 1988 is not getting the high idle at cold start then could be IAC Valve OR ECT sensor
ECT(engine coolant temp) sensor is a TWO wire 5volt sensor only used by the PCM

The dash board temp gauge uses a 12volt ONE wire SENDER, so not the same and no connection between the two except they both change with coolant temp