I get 11.6V on the IAC connector with the key on

 

I just verified proper operation of the PCV valve just to take that out of the possible problems.

So the CANP is only open when not at idle even with a warm engine? (engine runs fine when cold)?? If so where else can the engine be starving for air from if it runs great with the CANP disconnected when the engine is warm?

 

The best way to test the IAC valve is to run the KOER self-test and see if you get a code for it. If not it is more than likely a good one.

 

Do you have a stock air cleaner on it?

 

I did the KOEO test and got a SYSTEMPASS (with counting the engine light blinks). I get 11.6V on the IAC connector with KOEO. Yes this engine is completely factory original air cleaner assembly. I just did a basic tune up with air filter, plugs, wires, cap, rotor, MSD coil, IAC and no change in the idle or problem.

I will do some more videos with my GoPro tomorrow showing idle changes with the vacuum lines.

 

I have also replaced both the front and rear fuel tank pump Assembly's and the filter. Replaced the front tank about 5 months ago and rear tank last week and no change, still same problem no matter what tank I am running.

 

The 11.6 volts at IAC valve is battery voltage on that red wire with the key on and the power relay closed. That same red wire (361) goes to all of the fuel injectors, fuel pump relay coil and other solenoids. Sounds like the battery might be down a little.

Letting in air into the intake through a vacuum line might be just upping the RPM some. I have seen a lot of engines running ruff at low rpm and then smooth out when the RPM is a little higher. This can be caused by a plug wire not all the way on, a bad plug and so on.

 

I did the voltage check latter in the day and sure the battery was run down a bit with all the starting and stopping, going to have to let it run for a bit today to charge up.

I will double check all my plug wires, it does seem like a misfire when its running rough.

Going to have one more cup of coffee then I will be back out there. I will get video of it running and of the KOEO test.

 

As Bill noted previously the IAC is supplied battery voltage when the key is in the On position. The computer modulates the IAC by varying the On/Off duty via switching the return side to ground. Trying to measure the voltage at the IAC with the engine running with a DVM usually brings mixed results. You really would need an oscilloscope to view the On/Off duty cycle.

 

Tested the IAC voltage again KOEO today it was 11.55v and my battery was 12.24v I can get an O-scope from work tomorrow to do running check.

Here is the link for first start up of the day

https://www.youtube.com/watch?v=f30f...ature=youtu.be

 

First link is engine warm and then pulling the vacuum hose.

Second link is KOEO system test.

https://www.youtube.com/watch?v=dVMl...ature=youtu.be

https://www.youtube.com/watch?v=lWBh...ature=youtu.be

 

Well my alternator was on its way out, surprised I never got stranded. Was barely getting 12.8v. Just put a new one in and now getting 14.8v I wish that had something to do with the CPU and how the truck is running but no such luck. Truck still runs like crap.

 

So I got an O-scope from work today. Started the truck and pulled the connector and put the probe on it and hit auto set and I can see voltage jumping around, what readings should I be looking for?

Also when the IAC connector is on there is a weird humming noise comming from the air cleaner assembly, when I disconect the IAC connector to test voltage the humming noise goes away.

 

Not sure how you would test the voltage with the TPS connector unplugged.

 

Not testing the TPS I was testing the IAC voltage, rla said I really needed and O-scope to test that.

Should I test the TPS? What reading am I looking for?