ECU Coolant Sensor issues? (1998 Mustang GT 4.6L)

Sn95.Draconis-Kev

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I have had hot start issues with my Mustang for the longest time and i got a tip from a friend that it ought be the coolant sensor going to the ECU.
I knew that I had one on the left side of the coolant overpass tube on the front of the engine. I bought a OEM sensor and replaced it (sensor looked different which was odd to me but the connector still fit.) then my dashboard coolant temp gauge stopped working and i still had hot start issues.. So I put the old one back in and it was working again.

Did some more info digging and found out that it has two sensors. I removed the second one (right side of the overpass tube) and it was identical to the new one I ordered. So I out it in and now my hot start issues are gone! All good right? Not really. Now I have cold start issues.

Basically it takes about 5-10 seconds of cranking to start and it starts sluggish for a few seconds before it runs normally. This has always been the problem on hot starts until I changed that sensor. Now it has the exact same issue on cold starts, but not on hot starts.

Help?
 

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