Sensor mistery!!

[PorterzCustomz]

Since I got my 1990 TBI truck a month ago it has always ran ruff and backfired thru the intake. I replaced everything I could think of spent alot of money on it. Today I finally decided to unplug the coolant temp sensor in the front of the motor to see what would happen. NOW IT RUNS EXCELLENT!!! WTF!!??

I replaced the CTS with a new one and it did the same thing but when left unpluged the truck runs great what the hell is going on here!!??

With the sensor pluged in the truck runs fine cold and when the truck warms up then it runs like ****.

 

[PorterzCustomz]

no one?? wow

 

[80' 427]

Whats your coolant temperature?

 

[PorterzCustomz]

normal temp like idk 175-190 ish

 

[dyeager535]

Somethings going on when it goes closed loop.

You are dumping more fuel in when it's cold (open loop) when it goes closed, and starts using the O2 sensor to calibrate fuel, you start to run bad. Do a good visual inspection, tuneup, the works.

 

[PorterzCustomz]

Well, I did have to relocate the 02 to the botom of the collector for the dynomax headder, the 02 looked new. I did a full tuneup

 

[southernspeed]

Well, I did have to relocate the 02 to the botom of the collector for the dynomax headder, the 02 looked new. I did a full tuneup

If it's a stock O2 sensor, there's your problem. As DYeager says, open loop is good but closed is not getting good info. If you've moved your O2 down that far you need a heated O2 sensor.

 

[PorterzCustomz]

ohhh okay sounds good.