Engine surging, 250 degree intake, and -40 degree engine?...

[Cole94]

I've been on here before for this thing...
As per the title, I've got some surging from ~600 to 2500 rpm. Also, the IAT is reading 250 degrees. And the ECT is reading -40. I pulled codes, and got live data, they are coming shortly.

Thank you in advance for any help you can give.

 

[Cole94]

Got some codes...

 

[Cole94]

A recording of the datastream:



And a picture of it after a few minutes of idling...

 

[FR-425]

Looks to me like you have an open circuit on the 12v reference.

All of these sensors use 12v.

Start with the ECT and verify circuit integrity.

Just use a test light, unplug the ECT and with the test light connected to the negative terminal of the battery check for power at the connector. If good, move the test light to the positive side of the battery and check the ground. Oh yea, key on for theses tests.

If both check good move on to the IAT, repeat the test. If 12v and ground are good at all of the effected sensors, then you have multiple failed sensors. Doubtful but possible.

I suspect your going to find that you have a bad ground some where on the 12v reference circuit. Maybe the main ground strap from the frame to the engine block.

Simple test here too with the test light. Connect test light to the positive battery and touch the engine block anywhere, if the light doesn't light you have found your problem.

If the grounding issue is on the 12v harness only then you'll need to trace it down, i.e. look for rodent damage, chaffed-broken wire.

 

[Cole94]

Thank you. I will try this tonight.