5.0 Idle issues

[gadget73]

its just some connector number which I forget, but those two are what interface the main ECM harness to all of the sensors and actuators on top of the engine. The fuel injectors, throttle position sensor, EGR sensor, IAC, etc all run through there.

if you're in that general area looking at wiring, find the orange wire coming out of the harness that runs down to the oxygen sensors and male sure it is still bolted to the rear of the intake manifold or the back of the head. Thats the sensor ground wire for all of those engine sensors in the block and things will go goofy with it off. Pretty common for the eye to crack. Just put a new crimp eye on it and put it back on. Usually it will be one of the rear corner studs on the lower intake, the one with an extra nut on top.

[monotonorobo]

Ok, it was pin 9 which is the HEGO Ground

[monotonorobo]

It was a tps issue, runs with it unplugged but when it’s plugged up. Got a new tps and drilled the holes on it and th slowest I can get is 1.1 volts closed. Can anyone give me any insight on how I’d go about removing the idle adjustment screw? I can’t adjust it cause it’s too rusty. I already sprayed it and let it sit.

[friskyfrankie]

What did you use to spray it with? I'd try PB Blaster or Cree-Oil spray.

[sly]

1.1V should work fine. I think the operational range is like 0.75 to 1.25 and is read at startup each time anyhow, so that should work.

Yes, 0.9V is preferred, but it has some wiggle room.

[monotonorobo]

1.1V should work fine. I think the operational range is like 0.75 to 1.25 and is read at startup each time anyhow, so that should work.

Yes, 0.9V is preferred, but it has some wiggle room.

I don’t know if the computers learning but it shuts off after like a minute or two. I hold throttle won’t shut off at all. I’ll make sure the voltage is in spec again.

[monotonorobo]

1.1V should work fine. I think the operational range is like 0.75 to 1.25 and is read at startup each time anyhow, so that should work.

Yes, 0.9V is preferred, but it has some wiggle room.

1.173 fully closed and 4.4 WOT. Still don’t understand why it cuts off at the moment.

Edit: forgot to say if you hold your foot on the throttle just a bit for about 10-15 seconds it will idle longer with no sudden surges for about 3 minutes until it shuts off again. Also unplugged IAC before doing it and it bogged down but didn’t shut off so I plugged it back and and did what I mentioned above.

[sly]

Is the vacuum line to the MAP sensor bad and collapsing?

Is the throttle body clean? Is there a large amount of carbon buildup behind the throttle valve?

Also, did you fix that ground on the HEGO?

I'm not really sure what to go after on this one. I wonder if an accessory or the transmission are having issues and putting an odd load on things.

[monotonorobo]

Is the vacuum line to the MAP sensor bad and collapsing?

Is the throttle body clean? Is there a large amount of carbon buildup behind the throttle valve?

Also, did you fix that ground on the HEGO?

I'm not really sure what to go after on this one. I wonder if an accessory or the transmission are having issues and putting an odd load on things.

HEGO ground not fixed, just put in a new map hose a few weeks ago, throttle body is as clean as can be. I don’t really understand where to go from here now. I do believe it’s something intermittent because I drove it around the other day multiple times. TV bushing wouldn’t be causing this, could it? I checked IAC again too by putting it in drive and holding the brake to see if it would cut off and it did. It seems to cut off at the same time every single time. No sputtering, no misfire, no strong smell of gas. Just cuts off as if I turned the key off. I have a spare ECM that im gonna toss in and see what it does.

[gadget73]

Check it for codes, see if ther is anything there.

Possibly a coolant or air temp sensor fault can do stupid things on cold starts, but if that ground wire isn't connected the coolant and air temp sensor readings will also be wrong so fix that first.

tv bushing only kills the transmission, engine doesn't care. Do not drive it with a bad bushing though.

[friskyfrankie]

When you do get it running, if you have the plastic grommet for the trany linkage, I would STRONGLY suggest you swap it out for the brass grommet. At least that will permanently fix the problem of disintegrating grommets!

[monotonorobo]

Check it for codes, see if ther is anything there.

Possibly a coolant or air temp sensor fault can do stupid things on cold starts, but if that ground wire isn't connected the coolant and air temp sensor readings will also be wrong so fix that first.

tv bushing only kills the transmission, engine doesn't care. Do not drive it with a bad bushing though.

Alright I’ll check that HEGO ground and the only temperature sensor i didnt change out was the ACT. Still can’t check codes cause I can’t find out why the self test isn’t working, and it’s not the ECM. I’ll also say that since I put the new tps at 1.1v it ran better and didn’t sputter out or anything.

vid of it running. Idle went down but it was up a bit cause it’s cold out.

https://youtube.com/shorts/lrhcYsOEBqc?si=4_-oHynD8Bbyb4RZ

[slack]

Random shot in the dark but any possibility any wires or small vacuum hoses got borked while reaching down to replace the PCV and filter? When I did mine last time, I snapped a few of those vacuum hoses and didn't notice at first because they break so freaking easy and everything is crammed back by firewall.

[friskyfrankie]

Does sound like a possible vacuum leak.

[gadget73]

Did you shut it off, or did it shut itself off?