EFI hanging idle. Can't figure it out. New tps tests in range, new iac.

[Ranchtruck]

I would check the wiring diagrams to see if the computer normally gets a nuetral/drive input from the transmission range switch. If it does, and you don't have that hooked up, that can easily be the source of odd idle behavior.

I would look at adding wires before I started chopping wires. Hot rodders love chopping stuff out of systems so they run with the bare minimum, but that's often not conducive to good driveability.

 

[ren71]

I would check the wiring diagrams to see if the computer normally gets a nuetral/drive input from the transmission range switch. If it does, and you don't have that hooked up, that can easily be the source of odd idle behavior.

I would look at adding wires before I started chopping wires. Hot rodders love chopping stuff out of systems so they run with the bare minimum, but that's often not conducive to good driveability.

I agree, a lot of guys omit things like the VSS, neutral wiring etc. and while you may get lucky and have it start and run ok, it definitely won't be perfect.

 

[Ranchtruck]

I know on my Subaru EFI swap, it would occasionally stall coming up to stop lights if I coasted in and pushed the clutch in as I came to a stop. It was cutting all fuel while coasting, and when I pushed the clutch in it would loose rpms so quick that the computer couldn't catch it and start fueling again.

I finally wired in a clutch switch like it was designed, and never had the stalling issue again.

Small drivability issues like that can be caused by missing sensors like neutral, clutch, or vss.

 

[gunnibronco]

Me too!

I just finished putting an Explorer intake & RJM harness in my truck and am experiencing the exact same problem as the OP. If I depress the clutch with the rpms above 1500, they fall to 1500, then creep down to about 700. If I depress the clutch with the r's below 1500, they climb to 1500 & start the creep downwards.

The way my truck is acting is unacceptable. I can feel it pulling me around w/my foot off the gas. This is a real problem, especially in the ice & snow.

I bought a reman'd ECU (manual trans) from Advance Auto, I've had to warranty it because it was throwing a 15 & 96 code that would not clear. So the truck isn't driving right now, but when I get the replacement ECU, I'll try the suggestions above and see if anything fixes it. I'm hoping the faulty ECU is to blame and everything runs perfect when I replace the ECU. But that is probably not going to happen.

Please keep us posted if something works for you.

 

[70injectedbronc]

gunnibronco

Yeah let me know if that works for you. I'm gonna do some testing and checking tomorrow. Really hope to figure it out.

 

[broncojames]

I notes your in CDA I am just over the hill in Smelterville and planing the swap sooner or later along with a NV3550 swap kit is in shed waiting have tbird in driveway next to bronco.

 

[Broncobowsher]

TPS voltage just a hair under 1V
IAC installed correctly. You can flip them 180° and some do for clearance reasons, but that can mess with the design of the airflow and how it operates.
Base timing, Had a stroked 5.0 in a Ranger with a mustang EFI. At 12° base timing it had a hanging idle, would accelerate without throttle input when the VSS started going up. Set the timing to the proper 10° and it fixed the issues.

Just 3 things I have delt with for the same problem.

 

[70injectedbronc]

Haha broncojames that's awesome. We just went wheeling up in pinehurst last weekend. Small world. That'll be a sweet match up on your bronco. I've seen a few broncos in the valley. Hope to see it around.

 

[70injectedbronc]

And thanks everybody. Reading through everything and definitely checking it all out and will let ya know how it goes. There was a leak under the lower intake that's been bothering me so I dug into that today, repairing a leak in my radiator and am planning to have it all up and running by tomorrow.

 

[70injectedbronc]

And also I found that it didn't even have a pcv valve on it when I took the upper intake plenum off. Had the screen filter thing in and was completely full of gunk. But it had no pcv or vacuum line to it. So I got a new screen, pcv and grommett and am hooking it up to a vacuum plug that is currently capped on the side of the intake. Could help my issues I'm hoping....if not, it will take some crankcase pressure out which could have caused that intake leak. (or didn't help the matter anyway. Took a few pics, prob put em on tomorrow if I figure out how. Haha

 

[70injectedbronc]

Would not having a vss hooked up be the problem. I've omitted it as a possibility after reading with an automatic you don't need one but what are every one's opinion on it?

 

[DWALKER]

I just unpluged mind. It idles fine and has not hurt a thing. It is a little cold natured on cold mornings but that is fine. When I let off the gas it will idle down just like it had a carbon on it