Misfire/No start

Mustang5L5 · Mar 10, 2025

The spot is there. It would just need to be drilled/tapped for 3/8NPT, or just swap the crossover from a 96-98 intake over.

Pass side (the one drilled in the above pic) is for the gauge in the dash. Driver side (the one needing to be drilled) is for the ECU. If there is no reading on the ECU sensor, it will trip a code and default the factory fans to full on (which is why some folks claim this sensor is only for fan control). OP said he had an aftermarket set of fans, so likely didn't see this issue.

Driver's side coolant sensor needs to be installed. If you don't care about the gauge, extend the wiring and move it to the other side. You can try that as a test before committing to to drilling/tapping the crossover.

ttocs · Mar 10, 2025

Mustang5L5 said:
WHich one did you install and which did you leave out?

One sensor is for the cluster gauge, and the other is for the ECU. If your coolant temp gauge is registering normally, then you are missing the one for the ECU.

Given that you have a code for coolant sensor, i would bet it's the one for the ECU that's not hooked up. Given your symptoms, it would explain everything.

that was my concern as well.

DonTheMan · Mar 11, 2025

I tried unplugging the MAF sensor it didnt even want to start up, Also triple checked the wires were in there correct spots if thats what you mean by firing order. The sensor not in is the one on the driver side next to radiator hose.

Tried flooring to activate flood mode it stutters and keeps cranking, when I play with the gas pedal then stop it starts up after a while

DonTheMan · Mar 11, 2025

Ok then I should definitely get that in if its for the ecu I thought it was just radiator signal. Would it be ok to splice it into the other sensor or maybe it wont last/be safe?

ttocs · Mar 11, 2025

the fluttering of the gas peddling starting it I thought meant that it is needing more air to start. This should be controlled by the IAC, which is controlled by engine temp and a few other things. I would say to start with the temp sensor and see if that does not give the motor the correct temp to set the IAC/timing and get it running.