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2.9 to 4.0 swap HIGHT IDLE


lilfordrunner

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1987
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Ford
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Manual
Alright, I know I have posted this 100 times, but im hoping for some new eyes and fresh ideas on this…

I did a 2.9 to 4.0 swap into my 87 ranger
The Ranger is a manual, the donor (a 93 expo) was an auto.

I got the right ECM (one for a 93 manual) everything is hooked up, we have tested all of the sensors, they are all active.
How important is it to have the voltage directly on to what the book says? for example, if you are supposed to have 5 volts running to your TPS and you have 4.6 or similar readings like that…good or bad?

Vacuum tests show that I have good pressure, 20psi with NO movement in the needle, rock solid.
Ive got GREAT compression on all cylinders.

But the thing idles like a son of a gun and runs rich, and when you drive it the idle gets higher and higher and higher…if you turn the engine off and then try to restart it, it won't start right away, Im thinking its flooding when idling, so I have have to put the pedal to the metal and clear out the cylinders.

We are so close to getting this thing running cherry, but we just can't figure out the last step. It's somewhere in the wiring, I am 99% certain on that.

Im using the ranger truck harness and splicing it to the expo engine harness.
 


2002rangerv6xlt

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I feel your pain.

Unless there is some mechanical issue with your throttle body or IAC, I would guess that the issue has to do with one of your sensors. I'm guessing IAT, MAF or the two upstream O2 sensors (the downstream one does not affect fuel / air, it only monitors).

How do you know that you're actually running rich? It can be a little hard to tell sometimes from the exhaust smell alone if your cats aren't working or have been removed.

Is there an OBD-II port that you can plug into and read the real time data? If you don't have a reader I'd bet that the dudes at auto zone or advance would try to read your ECU for you. This would be the best way to gauge whether or not your sensors are all functioning properly.

Next best would be to try and diagnose your sensors the old fashioned way. But first I am curious as to whether you have your O2 sensors hooked up? What about your MAF (I don't know if this year has a MAF or not) ?

Is your coolant temperature sensor working? Does the car warm up properly? Do you have a thermostat installed?

If there is an IAC I would remove it, clean it and then get a can of the sprayable SeaFoam and clean out the intake from the throttle back. I had a similar issue on my 2002 3.0L and that fixed the surging problem I had one morning.
 

trail B2

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1986
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ford
Engine Size
4.0
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Manual
When I did my swap my biggest mistake was to not spend time with the donor vehicle.Thoroughly going over it to decide what has minor issues to help me diagnose them later.I solved my high idle issues after swap by getting a new tps and getting it properly adjusted.It was harder to diagnose because I didn't know if high idle was from the swap or not.Another thing I did was put in a switch to turn off the IAC valve when the engine got warm to lower the idle.This only works if the idle goes down when you unplug the IAC.
 

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