Crazy engine surging after new short block, help needed

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CJF said:
How do you know it's not blocked open? I'd actually remove the air intake hose and inspect, but ok. :meh:
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I have had the hose on and off quite a bit, changing the AFM/VAF 3-4 times, as well as had the throttle body off twice to adjust the TPS, and it has always had the flap closed.
 
I had one with a bad brake booster and bad iac do that once. you probably can fix this issue without the data but are you at all interested in installing that TOYOBD1 scanner to give you ecu data? Of course you can always unplug the ecu and and go pin to pin and read with a scope or multi-meter too.
 
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mudgudgeon said:
Faulty sensor?
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That is my guess or I have the wires reversed in the plug connector on the harness. I am picking up another brand new OEM coolant temp sensor this morning and will find out. I am not certain if it matters which pin goes into which side of the connector or not so might test that first before changing the sensor.
 
I was able to confirm using a spare engine harness I have that I have the wires in the plug reversed. I am not sure if that matters or not, but I am going to try switching the wires in the connector and plugging it back in to determine if that is the issue or if it is a bad sensor. I also have a new OEM sensor I was able to get from the dealer this morning.
 
hisandhers80s said:
I was able to confirm using a spare engine harness I have that I have the wires in the plug reversed. I am not sure if that matters or not, but I am going to try switching the wires in the connector and plugging it back in to determine if that is the issue or if it is a bad sensor. I also have a new OEM sensor I was able to get from the dealer this morning.
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Fingers crossed fer ya!
Troubleshooting. Such fun.
 
I am sad to report that replacing the coolant sensor with another brand new coolant sensor did not fix the idle surge. This leads me to believe I have an issue with the wiring between the ECU and the sensor. Anyone else have any thoughts? I did not swap the wires in the connector yet, so I may try that. What makes this strange is that I have no check engine lights when the connector is connected to the sensor and I get the surge, but when I disconnect the sensor, it will idle fine but a little high at 1,000 rpm’s and I get a check engine light. Not sure what to make of that. In my mind If there was an issue with the wiring, I should get the check engine light all the time.
 
Any chance this is related to fuel trim? You mentioned that the issue only happens when engine is warm. Perhaps this is when it goes from open loop to closed loop and starts using the front O2 sensor. With the temp sensor disconnected, maybe it never enters closed loop - I’m not certain of this. Have you tried changing or checking front O2 sensor?
 
I installed two brand new OEM o2 sensors, but I have tried unplugging both of them but that had no effect.
 
hisandhers80s said:
I would absolutely be interested in the TOYOBD1 scanner. I installed a new booster and master while the engine was out.

AND I am happy to report that unplugging the Coolant Temp Sensor let the truck idle at 1,000 for 30 minutes just now!
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if you had the scanner you could take a glance at it and it would tell you what the ecu is seeing for coolant temp, intake temp, etc. can unplug the ECU and measure the pins there for resistance, then after that load test each wire with an incandescent bulb, next check for short to ground and power.
 
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