1990 Dodge Dakota

Has the check engine light come on?

If the check engine light is on, there is a code stored in the computer. Follow these directions and let me know what you find.

NOTE: DO NOT START THE ENGINE.

With the key in the off position, cycle it 3 times to run, off, run, off, run, off, then run and wait. At this point, the check engine light will go off and then begin to flash. Each trouble code is a 2 digit number. Count the flashes. There will be a slight pause then it will flash again. Count the flashes again. The second set of flashes is the 2nd digit of the code. There will be a longer pause and it will start on the next code if there is one. The last code you will get is a 55. That lets you know it is done. Let me know what codes you get and I'll look them up for you to help identify the problem.

Let me know what you find.
Joe

I will get back to you tonight when I am home from work. I have the older trouble code list at home.

Take care,

Joe

Okay, here is the list:

12 - indicated that the battery or power has been cut to the logic module in the last 15 start-ups.

27- Injector driver control circuit open or shorted

Possible Causes
Bad connection or wiring - Check the wiring and connections between the fuel injector and the power module (or SMEC) and the injector contol lines between the logic module and power module. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.
Injector driver transistor failure - Check the injector signal coming from the power module (or SMEC). It should rise to about 12V when the injector is off and drop close to 0V when the injector is on. If it is out of spec, you may need to replace the power module.

35 - Radiator fan relay circuit is open or shorted
I don't believe you have a fan motor, but rather you have a fan clutch. I'm not sure why this is coming up.

55 - Sequence complete

If I had to guess, I would suggest starting by checking the wiring to the injectors. If there is a problem there, it could cause the idle to be a little crazy as you mentioned. You could also erase the codes and see it that changes performance and if the same codes come back. To see if you have fixed the problem that generated the code, your can erase all codes by removing power to the ECU (by disconnecting the battery or otherwise) for about 10 minutes. This will clear the ECU's memory and generate code 11 and code 12. Crank or start the engine to see if the code in question returns. The code 11 should disappear as soon as the engine is cranked and the code 12 will disappear after 15 on/off cycles.

Let me know what you find, and sorry it took so long to get back to you. WHAT A NIGHT!

Joe

It could be causing a rich or lean mixture that has an affect on the idle.

In 1990, they had throttle body injection. Is yours different?

If you have a carb on it, someone has changed it. Now that I know that, I'm not sure what all was changed. Does it ever idle down to where it should be? Have you tried adjusting the curb idle speed?