2.9l V6 Automatic '88 rough cold idle/dies when cold


Stamos86

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Hey! I am not a mechanic by any means, but I am a mechanical engineer. So I like to figure things out and I have been learning a lot by working on this truck.
I got my 88 Ranger recently and at first it wouldn't run much at all. It is kind of a family heirloom as they bought it in 87 and have kept it since. However it had been sitting for 5 years before I recently acquired it.
Figured out the fuel tank was rotted out so replaced pretty much the whole fuel system to and from engine. I had a mechanic do that part. I am not sure that the fuel pressure regulator was replaced though. The fuel injectors were cleaned, and 2 were replaced. After that it was running, but not well. Practically zero acceleration and still died a lot. Replaced the MAP sensor, TPS, Spark Plugs and wires, distributor cap and rotor, and IAC. So it has been getting better.
My issue now is that, when cold, it idles rough and sometimes dies on its own. If I try to drive it without letting it warm up for a few minutes, when I accelerate, almost nothing happens and when I let off the pedal it dies. This will happen a few times before I guess it is warm enough for some reason.
1. I thought it may be the EEC-IV feedback loop not operating correctly because I know the O2 sensor at least has been disconnected/bypassed somehow. There are a lot of sensors that have been removed from the looks of some of the loose cables under the hood.
2. There is also something disconnected that I am not sure what it is (See image below).
3. There was some oil on the spark plugs when I removed them. So that means, and correct me if I'm wrong please, that either the valve cover gasket is leaking, O-Rings in the spark plug wells are leaking, bad piston compression rings, cracked piston, or worn valve guides. Could it also be something else?
So my questions are basically:
1. Could the EEC-IV not having all the information it needs cause this issue? If not, what would it improve by me getting it back to where it needs to be? I would also need to know where the EEC-IV is, because the O2 sensor in it now doesn't connect to anything and I don't see a connector to attach it to. I may have to run a new connector from the EEC, right?
2. What is the sensor/thingy in the image below with the wire to nowhere, and what does it do?
3. I know i need to fix the oil on the spark plugs issue. Would this cause my issue from above? How would you do it? Just replace all the stuff I mentioned? I also read that I may be able to get an updated valve cover that doesn't have the same issues of the original.
4. Seems like it would be a good idea to go ahead and replace the remaining fuel injectors and fuel pressure regulator. Especially if it may be affecting my issue. What do you think?

From my research I have also heard it may be affected by:
PCV valve
EGR sensor/ Valve
EVP sensor
Ignition coil
Ignition timing
Transmission Vacuum Modulator
Intake air temp sensor?
ECT coolant temp sensor
Torque convertor

Also may be important to note that the CEL comes on around 10 minutes after driving it. I read that may be the O2 sensor.
Any advice would be great. I have a really good time working on this truck and would love to get it running well.
Thank you!
 

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rusty ol ranger

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Change your coolant temp sensor (the 2 wire plug one) and try that. Did you pull codes?
 

Bird76Mojo

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That sensor is just an oil sensor and it turns on a light on the dash if all of your oil pours out somehow.

Without the O2 sensor hooked up, the truck will never really run right.

Sounds like you could use the help of a buddy that was a little more mechanically inclined in the automotive area..
 

Stamos86

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Change your coolant temp sensor (the 2 wire plug one) and try that. Did you pull codes?
It doesn't give me any codes either way. 😕
I will try changing the coolant temp sensor tomorrow. Thank you for your response!
 

Stamos86

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That sensor is just an oil sensor and it turns on a light on the dash if all of your oil pours out somehow.

Without the O2 sensor hooked up, the truck will never really run right.

Sounds like you could use the help of a buddy that was a little more mechanically inclined in the automotive area..
I thought so. I will get the 02 sensor hooked in and see what that does. I agree I could use some help from someone with more automotive knowledge. I'm short of one at the moment though 😔. So I'll keep coughing along with my attempts to then. Thank you for your advice!
 

Bird76Mojo

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The O2 sensor should have it's own wire attached to it with a plug on it. It will plug in to another harness that comes from the back of the engine nearby.. A round-ish plug..

The O2 should look something similar to this:

 

Stamos86

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The O2 sensor should have it's own wire attached to it with a plug on it. It will plug in to another harness that comes from the back of the engine nearby.. A round-ish plug..

The O2 should look something similar to this:

Yeah i've got a new sensor to put on and it looks like that. I'll just have to find that harness that comes from the back of the engine.
Apparently the person/people who have worked on it before me were just pulling out sensors and bypassing things in order to get it to run at all instead of taking the time to make sure it's right.
I'll look for that harness this afternoon. Hopefully it wasn't done away with somehow. Thank you!
 

rusty ol ranger

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O2 shouldnt cause issues when cold...
 

Bird76Mojo

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rusty ol ranger

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Stamos86

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Hey guys,
So I got the ECT sensor installed. No luck with my issue though. Any other ideas? Maybe the intake air temp sensor?
My pressure gauge should be coming in today so i'm going to see if that tells me anything. It probably will, but I don't know if it will tell me what is causing this particular issue.

I also got the new O2 sensor put in, but I can't hook it up yet as the connector, which was connected to nothing, was apparently laying on something hot and melted to the point I can't plug in the sensor. So I will have to order a new terminal and wire it in.
 

rusty ol ranger

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You really should pull codes
 

Stamos86

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I did try to pull the codes but it doesn't show any. I will try again this afternoon. The CEL only comes on after driving for 10-15 minutes and then goes away after shutting it off. Do you know if this truck is supposed to store the codes? It doesn't seem like it does.
 

rusty ol ranger

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Spend 30 bucks on an ford EEC IV code reader.

You should atleast get a code 11 (pass) code.

Yes it should also store codes
 

Stamos86

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Yes. Apologies. What I meant was that, when pulling the codes, the only one i get is the pass code.
I got the O2 sensor hooked up now.
Apparently there is a transmission fluid leak. I am looking into where from. Somewhere around the torque convertor.
The vacuum pressure showed no issues. Steady at 17 and reacted properly when i pressed the accelerator to 2500 rpms.
 


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