Sorry for the confusion - that's the idle with the IACV unplugged.

 

First, try the idle setting procedure in that shop manual and checking the 5V reference voltages.

Where did you buy the IAC, what brand is it, and what is the part number?

 

EGR sensor yellow wire - 5V
MAP sensor yellow wire - 2.5V

I think we may have found something funky if this wire is supposed to be 5V.

Not sure what brand the IAC is. I will get to the idle procedure later.

Thank you so much for your help and patience so far - you are saving me here haha.

 

The shop manual I have isn't great, but is the 2.5 wire on the right side if you are looking at the pins of the connector and the clip is pointing up?

The 2.5V can mess up the MAP signal to the ECU, because the MAP sensor signal is what the ECU uses to estimate the air flow into the engine. Now why does that wire have 2.5V. Unplug the other 3-wire sensors one at a time to see if the 2.5V increases to 5. The MAP, TPS, and the EGR lift sensor are the only three items I see that share the same 5V reference line from the ECU.

If the 2.5V remains, then I'd trace that yellow wire back to where it splices into the other sensors and look for corrosion/damage along the way. Look at the plastic loom for signs of wear or where it could be pinched.

 

 

Not sure what you are trying to show in the pictures.

 

Sorry, you were asking what color wire comes out of what position on the sensor/connector. I got 2.5v by measuring the yellowish wire going into the map, and I show it going to the connector.

I tried unplugging either the tps and the egr sensor and neither affect the reading of that wire.

 

I tried chasing that MAP wire that reads 2.5v back, but it goes directly into the harness very near to the cabin surrounded by plastic sheathing. Should I tear into it and examine it?

 

You might want to back-probe one of the good 5V references nearby, then backprobe the red/wht wire to the map sensor. Then run a jumper wire between the two. Essentially, you are sharing 5V from another sensor (EGR or throttle position) with the map sensor. Make 100% sure you are tapping into the 5V of another sensor. You can use a t-pin or regular needle to back-probe. A wire with aligator clips would work to jump. If the idle behaves normally, then you can keep tracking that wire.

To trace the wire, you might have to start at the ECU then work backwards towards the firewall. If you found that shop manual, pin D19 on the ECU should be the red/wht wire, then you can work back towards that grommet. That shouldn't be a long run to track. That wire should branch off to the TPS and EGR along the way. It might be right at the ECU connector and could be a prime suspect for the poor connection.

Hopefully you are close to solving the problem.

 

I'm sorry to report that upon retesting the MAP it appears normal - blue/wht (far left wire in my pic) reads a small value (car is off, .004v or something) wht/blue wire (middle) reads 2.5v (the one I was confused about, and thought was the 5v reference) and the red/wht wire you spoke about (far right) indeed reads 5v.

Not sure where to go from here.