[4.0] Bad sensor or bad ECU?!

Runs too lean at idle and dies. It revs fine and has no adverse sounds.

Unplug Mass Airflow Sensor for 10 seconds and replug fixes issue entirely.

Replaced the sensor for the low, low price of $200USD to be met with the same issue. Unplug to make the computer go into fail safe mode and it idles great.

I've had this engine all apart replacing head gaskets and it sat without running for a long time, but I'm 100% sure this is a sensor issue as the engine operates fine when the computer is running in fail safe mode. I've been driving it to and from work without issue.

Could the O2 sensors be causing this? Don't know if I can properly illustrate how tired of throwing parts at this truck that barely has 110k on the odometer.

Is there anyone close by with a diagnostic tool? HawkEye, Nanocom, Testbook...

srtgray said:

Is there anyone close by with a diagnostic tool? HawkEye, Nanocom, Testbook...

Click to expand...

Not sure, I mostly get told to go away if I bring a landy to a shop around here.

Most I've put on there was a code reader for the check engine light which gave me the oh-so-valuable "misfire causing excessive emissions."

Most likely cause is a low reading Maf,but he only real way to sort it out is by getting some live data displays going.If it is low reading maf the fuel trims wont cope,their pulse width being too narrow to get the oxy sensors to switch up rich.This then logs loads of oxy sensor and missfire codes - which can be misleading... The live data is key,and as an example you need 22-25kgs of airflow at idle,engine hot,all loads off.

Replaced some decrepit looking main fuses under the hood for noticeable improvement.

Still lags under throttle and runs a tad lean.

Leads me to believe more wiring issues.

Update.

Throttle body wasn't tight enough causing vacuum leak.

Someone shoot me.