ICM purchase

[emo666]

Where's the best place to buy a reconditioned ICM for a 1986 4 cyl 5 sp ranger? I see a lot of suppliers out there on the net but want a good quality one.
I've got a rough idle problem that lasts a minute or so then straightens out but happens every time you shut down and restart. I.ve replaced oxygen sensor and temperature sensor. It used to do it then straighten out but now it's effecting the normal performance.
I don't want to start changing everything out cause I read that it is probably the ICM----BUT---- ??????
Engine rebuilt about 40,000 miles ago --sounds ,starts and idles great--just starts up idles up then settles----then rough idles and blows black soot out the exhaust for a minute then goes back to idling smooth. It used to do this and run good if you let it go thru it's routine but now it's not clearing up and is missing and bucking while normal driving.

 

[RonD]

Just FYI O2 sensors are not used on start up, on cold engine they are not used for at least 10mins, warm engine 2 or 3 mins before computer looks at them.

I would first do the "worksheet" checklist before getting a new ignition module.
Read here and print work sheet:
http://www.therangerstation.com/tech_library/TFI_Diagnostic.html

But because of the black smoke(rich mix) I would lean more towards fuel issue than spark.
If it does it more when engine is restarted within an hour then it could have a leaking injector, fuel is draining into intake and on restart engine is flooded causing the rough idle and black smoke until it clears.
Or the Fuel Pressure Regulator(FPR) can leak and fuel is sucked into the engine via it's vacuum line when restarted, causing rough idle and black smoke.

FPR is easy to check just pull off it's vacuum line and smell it for gas smell, replace FPR if there are signs of gas in the vacuum line.

Leaking injector can be detected by removing air plenum at the intake after engine is warmed up and shut off, smell for gas in the intake, shouldn't be any smell, injectors are off.

And of course a fuel pressure test can tell if there is a pressure leak

PCM(computer) has different startup routines for cold and warm engine as far as fuel goes.
Do you get the rough idle/black smoke on cold starts exactly the same as warm starts or are there differences?

 

[emo666]

Just FYI O2 sensors are not used on start up, on cold engine they are not used for at least 10mins, warm engine 2 or 3 mins before computer looks at them.

I would first do the "worksheet" checklist before getting a new ignition module.
Read here and print work sheet:
http://www.therangerstation.com/tech_library/TFI_Diagnostic.html

But because of the black smoke(rich mix) I would lean more towards fuel issue than spark.
If it does it more when engine is restarted within an hour then it could have a leaking injector, fuel is draining into intake and on restart engine is flooded causing the rough idle and black smoke until it clears.
Or the Fuel Pressure Regulator(FPR) can leak and fuel is sucked into the engine via it's vacuum line when restarted, causing rough idle and black smoke.

FPR is easy to check just pull off it's vacuum line and smell it for gas smell, replace FPR if there are signs of gas in the vacuum line.

Leaking injector can be detected by removing air plenum at the intake after engine is warmed up and shut off, smell for gas in the intake, shouldn't be any smell, injectors are off.

And of course a fuel pressure test can tell if there is a pressure leak

PCM(computer) has different startup routines for cold and warm engine as far as fuel goes.
Do you get the rough idle/black smoke on cold starts exactly the same as warm starts or are there differences?

Makes no difference ---cold or warm

 

[adsm08]

Why in the world would you want a reman TFI module? Just go buy a new Motorcraft or Bosch unit.

It wasn't a terribly reliable design due to it's use of the primary heat generator under the engine as a heat sync.