87 ford ranger 2.9 efi idle


Old 08-14-05, 07:21 PM
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Join Date: Mar 2002
Location: kentucky
Posts: 267
Unhappy 87 ford ranger 2.9 efi idle

Re: 87 Ford Ranger, 2.9 Electronic fuel injection. I just purchased this vehicle and it appears to be a fair truck. The problem is that when you start the engine it searches for smooth idle and it won't idle when in gear and it dies when you give it gas until the engine warms up. The seller explained to me that this "thing a ma jig" needs to be replaced and that should cure the problem. The problem is I am no mechanic and I have no idea what the part is. I took a picture of it, but attachments are not allowed, so I will do my best to describe it. As you face the front of the engine, there is a "hose" about 4" in dia . The hose connects to the front top of the engine via a radiator clamp to another metal piece and that piece is bolted to the engine. The part that I am concerned about, is black plastic material and is attached to the the left side of the metal piece that the hose is attached to with two phillips screws. There an electric plug that is connected to this piece, and there are three wires from it and it looks like it goes back to a wiring harness some where. The piece itself is about 2 1/2" tall and about 1 3/4" wide. The plug that goes to it is about 2 1/2" tal and about 2'' wide. Perhaps with this info someone could help me. It looks like all a person would have to do is remove the two phillips screws to remove and replace, if in fact this thing will fix the problem. As always, thanks in advance for any advice.
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Old 08-14-05, 07:47 PM
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Join Date: Oct 2003
Posts: 352
That sounds like TP sensor (throttle position sensor) be careful on replacing this so fast? I would check for a vacuum leak first. Rolling Idle
Old 08-14-05, 07:52 PM
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Join Date: Oct 2003
Posts: 352
Spray some WD40 or Choke cleaner around the lower intake manifold.While the engine is running. The idle should smooth out if leak is present. I have seen these gaskets leak. Sorry I forgot to say this in the first post.
Old 08-15-05, 05:38 AM
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
Welcome to the Ford EEC-IV Speed Density Wandering Idle Club!
Wandering idle is very common on these early EFI engines (Pre-Mass Air)
Speed Density means the computer (in this case an EEC-IV) does not get an actual reading from a sensor (Mass Air Flow sensor) of how much air enters the engine
It infers it from the Manifold Absolute Pressure and the Speed the engine is turning (Density and Speed)
Thus a wandering idle is very common

Although there is a chance the TPS is bad, I also would do some tests first
It's not a good idea to throw parts at it and see if it gets fixed
There can be many reasons for wandering idle, and if it's the sixth part you change that'd get kinda expensive

1) Pull the codes
The EEC-IV computer stores many trouble codes w/o turning on the Check Engine Light
Before doing any sort of work like this, or any diagnosis you need to find out what the computer says
Sometimes that's not much
But that is where you start

Have the codes read, sometimes a DIY auto parts place will do it for a small or no fee
Or borrow a scanner
Or if you have a volt meter you can DIY
Let me know if you want to try that and I'll post up the procedure

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