Mods are in my sig. anyways I go out start my truck up and it doesnot wanna start unless flooring the gas pedal. Runs really rough and really rich for about 15 seconds or so then it smoothes over. By the way i unplugged the IAC sensor and the ECT SENSOR and adjusted the throttle screw to make it not stall out and it’s very much driveable like this. Just runs really rich on start up and then smooths over. No power loss or anything.

If I keep the IAC SENSOR ECT sensor plugged in it starts right up no prob but then runs like it’s extremely lean and bucks and misfires and no power. If the ect sensor is plugged in it runs lean when unplugged runs really rich. The IAC works as it should when it’s plugged in

I have replaced the ect sensor and made no diff at all. I checked continuity at the plug and the sensor and have it. Also cleaned the iac do not believe that to be the problem. I have correct fuel pressure and good spark. Any help would be appreciated

 

Plug everything back in and then pull the battery cable for 30 sec. Then start it up, run it down the road and back, and then pull the codes from the computer.

 

Have tried that quite a few times no difference at all.

 

I think you missed this part!


He wanted you to plug everything back in like the factory had it - we don't care how it runs at this point.
Pull the cable from the battery for 30 sec. to clear ALL COMPUTER CODES, and hook it backup.
Then take it for a spin say 20 miles, then pull the codes from the computer.
Dave ----

 

I’ve done that as well codes were
21r coolant temp sensor out of range
25r knock not sensed
41r HEGO (HO2) sensor low voltage system lean

 

Engines are easier to diagnose over the internet when all the codes are listed, and in order of test. Thanks.

KOEO - (O) Self-Test Codes =
KOEO - (C) Continuous Codes =
KOER - (R) Self-Test Codes =

 

Check the reference voltage at your disconnected ECT connector with the key on, and post your measurement. Thanks.

 

If you were trying to to disable sensors to get the riches possible micture those would be the ones to do it. That is the perfect storm.

Coolant temp sensor no signal tell the ECU that engine is cold richens the mixture.

No knock sensor signal ECU richens the mixture to insure no detonation can occur.

No O2 sensor ECU reads lean richens the mixture.

No wonder it wont run right.


Replace the failed sensors and your issues will go away.

 

I was thinking the O2 & Temp would be the 2 big ones to change out as a start.
No knock I would think no spark advance so it would be a dog and could play into the MPG but I have been wrong before.


But as vjsimone listed, need to list in the order they test in and come up.
Dave ----

 

I’ve replaced the ect sensor. And when it runs really rich with the ect unplugged and the IAC unplugged it runs damn good ! Just starts up rough and runs like it has a huge cam for about 15 seconds after that no performance issues at all. With everything plugged in it’s super lean including the new ect sensor

 

Enriching the mixture by unplugging stuff is not really an ideal situation...
Speed density systems are notoriously sensitive to cam changes. You can't just throw any old cam in and expect it to run right.

 

You will get code 21 if during the test the engine temp was less than 180 degrees, or more than 250 degrees. If the engine was fully warmed up, and the sensor was plugged in when the test was run, then you can unplug the ECT sensor plug, and use a digital voltmeter, read the two pins in the connector with the key in run, engine off. You should read 5 volts. If you don't, you have a wiring problem on the signal wire. You can then leave the voltmeter connected, and then short the two pins on the connector with the key still in run. You should read zero volts with the pins jumped. If you still read 5 volts, the signal return wire to the ect is bad somewhere.

I would not worry about the code 25. If you did not goose the engine when it told you to, then you will get a couple of different codes, and if you did goose it, you can still get the knock sensor code. There are ways to get rid of it, but it's not that important right now.

Code 41 That means the voltage from the oxygen sensor was low for a extended period of time. Either the engine is running extremely lean, or the sensor is lying. Since you think it's running lean, the oxygen sensor may be verifying that. You need to check for vacuum leaks, the EGR valve my be leaking by, fuel pressure should be around 38 psi.

Each time you mess with the IAC, to keep it running you must be turning the screw on the throttle body. That's ok for experimenting, but before you hook the IAC back up, you should adjust the throttle back to were the engine barely runs and eventually may even die with the IAC unplugged. Then hook the IAC back up and let it take over. It will take a couple of drives before the engine learns to control the idle again.