94 4.0 high idle after engine swap

[94b2300ranger]

Well it runs I do have one issue, it has a high idle, Around 22-2300 RPM's. I checked all my connections to include vacuum.

Pulled a 2.3 and put in a 4.0, swapped everything for the 4.0, harness computer and ECU. It fired right up after priming the fuel lines. CEL flashes off and on, going to pull codes and get back with more info.

 

[BlackBII]

If there are no vacuum leaks, then either the throttle plate isn't closed all the way or the idle air control valve is being retarded.

 

[RonD]

Good Work

IAC Valve is used by the computer to set cold and warm engine idles, it is basically a controlled vacuum leak.
Unplug IAC Valve wires while engine is idling, cold engine should stall, warm engine should go down to about 500RPM, but may also stumble and stall.
If idle stays high then you do have a vacuum leak, OR........throttle plate may be open too much, make sure throttle cable or cruise cable is not holding it open.
On the throttle linkage there is a screw that "looks like" an idle screw, but fuel injected engines can't use idle screws of course, so it isn't, it is an anti-diesel screw.
Engine needs to be warmed up to adjust this screw, and its adjustment also effects TPS(throttle position sensor)
With IAC Valve wires unplugged, it should be set so engine idles at about 500RPM when fully warmed up
When you plug IAC back in RPMs should go up to 625 with manual trans computer or 750 with automatic trans computer.

On cold start computer should set 1,100RPM idle then start dropping from there as engine/coolant warms up, colder outside temp = higher idle

 

[94b2300ranger]

So I finally got back to working on it, a couple of things, It idles at 22-2300 rpm still until i disconnect the IAC, then it idles at 1100 rpm. Also i can fire it up on a cold start and it will run, but if i turn it off, it won't start back up, even if i prime the fuel lines.

I was able to take it for a very short drive, and it performed perfectly. Just trying to figure out these issues.

I appreciate all the help that you guys are providing.

 

[monstermazda]

What did you reuse from the 2.3 motor like maf map ect and is it auto or standard I have seen some cars go from auto to standard amd have high idle because of torque converter and stuff.

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[94b2300ranger]

What did you reuse from the 2.3 motor like maf map ect and is it auto or standard I have seen some cars go from auto to standard amd have high idle because of torque converter and stuff.

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I didn't use anything from the 2.3, I was able to get everything from the 4.0 donor truck. Including the manual trans, the 2.3 had a manual trans, but i didn't use the harness or ECU from the 2.3. All 4.0 parts, Harness, ECU and MAF.

 

[94b2300ranger]

Also I my CEL works/turns on.

 

[BlackBII]

If it's idling at 1100 with the idle air control unplugged then you have a vacuum leak, the throttle plate isn't closing all the way or the idle air control valve is stuck open.

Have you checked all those?

 

[monstermazda]

X2 what bb said could be a vacuum leak. Put a gauge on it. Or off time

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[94b2300ranger]

If it's idling at 1100 with the idle air control unplugged then you have a vacuum leak, the throttle plate isn't closing all the way or the idle air control valve is stuck open.

Have you checked all those?

I've checked for a vacuum leak and the throttle plate, which seems fine. With the IAC connected it idles at 22-2300 rpm, when disconnected its at 1100 rpm. I can fire it cold start instantly, and then shut it off after maybe a minute and then it doesn't want to fire, it doesn't come close to operating temp. I don't use any type of starter fluid.

 

[monstermazda]

Have you check timing

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[94b2300ranger]

Going to get a IAC since i don't know the condition of it. Hoping this will solve my problem. It fired right up this morning, so i decided to take it for a drive and I noticed hesitation in power at WOT. That is with the IAC disconnected, reason i left it disconnected is cause of the high idle issue. I'll report back later with my findings.

 

[94b2300ranger]

So I replaced the plugs, wires, IAC and air temp sensor with new parts and swapped out the coolant temp sensor from my 2.3 since i couldn't get a new one and nothing has changed. I checked the oil and it has fuel in it, I was able to light the dipstick on fire, which leads me to think i have a stuck open injector or bad Fuel pressure regulator. When i pulled the old plugs they were all black and had a strong fuel smell.

What do you guys think?

 

[94b2300ranger]

So I tried the FPR vacuum test and all is well, doesn't smell like fuel and it's not sucking fuel. I pulled the upper intake manifold and put my meter to each injector and all 6 were between 16.0-16.2 ohm's, so i believe the injector's are fine. I'm at a loss at this point. Going to do a compression test and a leak down test.

Any suggestions?

 

[94b2300ranger]

So after testing the injectors, they ohm out between 16.0-.2 across the board, checked for leaks and clogs. They seem fine to me. I was messing with the plug wires on the coil pack and i pulled wire 4 from the pack and then 6, went to pull 5 and it jumped the arc to my finger, but didn't shock me. The spark was orange/light orange.

It starts no problem on cold start, but doesn't start after. So this is what i think. After the cold start, I shut it off and try to start it again but with the weak spark i'm not getting full detonation when trying to start it again and i'm just dumping fuel into the cylinders and compressing it past the rings, which would explain the fuel in the oil and no restart. So I ordered a new coil pack and it will be here Thursday.

Does this sound like it could possibly be my issue? Or am I just losing it trying to find this problem?

As for the high idle issue, I'll tackle that once i figure out the run issue.