Chevy 454 rough running when warm help!

[Skrmbld]

Hey guys. Need some advice on diagnosing a motor problem on my tow pig. 1992 K2500 suburban with the 7.4l 454 big block. Truck has been a perfect truck for a long time. Started it up the other day and it cranked right up but immediately died. Never happened b4. Cranked it again and it was sputtering a bit. Drive it about a mile and damn thing is sputtering and has no throttle response once it reached operating temp. Black smoke coming out of tail pipe and was back firing. Only way I could get it to start againwas holding the pedal to the floor. Could smell it was running very rich. Limped it home and parked it for the day. Pulled all the plugs and all but three were fouled out. Had carbon globs on the tips. Changed to new plugs, wires, rotor button, distributor cap, and pvc valve. Cranked it up and she was purring so sweet. Thought it was fixed. Just let it sit and idle and once it warmed up, the motor reves up to about 2000 by itself and the injectors were dumping tons of fuel (TBI). Exhaust was light white/grey and was very strong of unburnt fuel smell. Hit the gas and it sputters and cut off. So I'm thinking coolant temp sensor. Replaced both sensors, one on drivers and other on passenger head. Filled up with coolant and fired it up. Same results as b4.
What do I need to check or change out? What is causing extra fuel to be dumped into the motor once it reaches operating temp?
Any help or even smart ass suggestions such as buy a Ford would be appreciated. Thanks John

 

[4byfan]

The tbi 350 has a temp sensor in the front of the intake that will make it do the same thing u are describing. Not sure if the tbi 454 has it in the same place or not.

 

[Skrmbld]

I just looked and sure enough there was another temp sensor close to the waterneck for the upper radiator hose. Why does it need three coolant sensors? I know ( at least I think I know) that the drivers side head coolant temp sensor works the temp gauge in the instrument cluster, the passenger side head coolant temp sensor controls the fan and I thought the ECM. Wonder if the coolant temp sensor in the intake really controls the ECM. Thanks for the input.
Anyone else have any suggestions before I just start replacing sensors?

 

[30th6]

Re:

X2 on coolant sensor on intake.

Sent from my SCH-I545 using Tapatalk

 

[muddinmetal]

Also check the hose from the back of the tb to the map sensor jic

 

[4byfan]

That sensor costs less than 10$ and I would put money on it that that's your problem. From what u described its doing that would be my next move.

 

[Skrmbld]

I just picked up the coolant temp sensor that goes into the intake. Hope it gets it. I'll post up results. Thanks for the info guys.

 

[Skrmbld]

That seemed to do the trick! It's running great even when warmed up. No extra rich fuel exhaust smell. Can't believe that there are theee coolant temp sensors on that big block. Guess I was on the right track changing those sensors, just not the right one. Thanks to the guys who posted up advice. Y'all kept me from setting her on fire out of frustration! If we run into each other on the trail, first cold beer is on me. John