You said something about the TPS...

The idle-control system switches on & off based on the TPS, so if that is making false signals, maybe(?) the idle-control system is trying to become active at part-throttle. Then when you open it further, the idle-control turns off & it doesn't surge?

But remove air from the cooling system too.

 

JimBlake, you are correct. At very low to mid throttle the car surges, up, down, up down. Once I give it more gas, and then push the throttle to wide open, the engine revs normally.

 

In that case, you'll want to set up the TPS properly. I don't remember the details, but if you search you'll find a procedure. Something about what voltages you get when the throttle is closed & open & smooth sweep of voltage in between.

 

Update 11-23-2012

So, today my buddy and I checked all the vac lines again. They checked out good. Everything is connected correctly.

Then, we swapped out the entire throttle body from another used EX I found at a junk yard. Started the car and it idled perfectly. Then I gave it some throttle and the same exact issue occurred that I was having previously. A surging of the RPM's at low to mid throttle.

So, taking this forums advice, I took off the Idle Air Control Valve, cleaned it with some throttle body cleaner. I did however notice that the screen on the one port hole was completely missing, almost like it rotted away. So, I started the car, and the same exact throttle surging occurred.

I then pulled the codes and came up with a a #1 (Oxygen sensor code) as well as a #14 (IAC). Cleared the codes and those 2 codes came back each time. I am pretty sure the o2 sensor is not causing this weird throttle issue. I am assuming it is the IAC valve. Do the symptoms I have correlate to an IAC valve problem? If so, why?

See the video below. Can anyone help me verify I am reading the "blinks" correctly. Thanks!

 

Looks like code 10 and code 14. The first one is a long flash, not short. Code 10 is for the IAT (intake air temperature) sensor.

 

Ok, cool. I just went out to the car again and did a test...

I unplugged the TPS sensor and read the codes. I then pulled a #7 (TPS sensor problem). So I verified that the TPS is quote on quote working.

Now since it is a code 10, could my low throttle surging problem be caused by the IAT. From what I read, the IAC valve doesnt seem like it would cause my issue, however the ecu is saying there is a problem with it.

 

Maybe there's a problem with the wiring to the TPS? Or the wiring to the IACV? Try checking the voltages you get from the TPS, not just swapping it out. If you get a bad signal from the TPS because of a wiring problem, that explains why the new one didn't help. I had suggested measuring the signal, not replacing it yet.

The code 14 means the idle isn't controlling steady at the proper RPM. Doesn't necessarily mean the TPS is bad, it might be other things like dirty throttle body (which you've already cleaned?) That stuff is more common than a bad IACV.

You say your idle is nice & stable. What does your idle do when you unplug the wiring harness from the IACV? It should drop down to about 550rpm, as long as EVERYTHING is turned off (headlights, AC, blowers, music, everything) and the engine is warmed up.

 

Throttle body is clean and good to go. I am going to go out and measure the the voltage on the TPS wires right now. Will be back in a few with the results. Stay tuned!!

 

I haven't done the TPS adjustment myself, so you should probably search for some posts about it by someone who has done it.

 

This problem is quite a bear.