TBI 454 running rich
 

Hi everyone.. first post here... I just bought an 87 1ton srw. has tbi 454 with th400 trans. as soon as I bought the truck it went on the trailer, home and into the garage. So I haven't driven it more than a test drive. Im in the process of taking off the 3 inch body and 6 inch suspension and just putting a 4 inch suspension on the truck. so while ive been waiting for springs I started going over the truck and giving it a tune up. pulled the plugs and almost every plug was black and even when the truck was running it just smelled extremely rich. so ive changed the plugs, wires, cap, rotor, distributer (bc the damn screws stripped for cap), coolant temp sensor on intake and the o2 sensor. Is there anything else you guys can think I should change or check? The motor was rebuilt back in 01 but only has about 30k on it. it also has an edelbrock rv cam in it and bored .30 over, stock intake and from everything else I can see it seems to be stock. thanks for any help

Re: TBI 454 running rich
 

check the "Map" sensor if its bad or the vacuum line is off or leaking fuel will go full rich. Should be huffing black smoke out the tailpipe if it has a problem.

Desert

Re: TBI 454 running rich
 

that was probably going to be my next piece to change. with the truck being nearly 30 years old ive almost come to the conclusion that changing anything sensor or fuel related wouldn't be a bad thing. I also noticed that the two sensors on the heads were in pretty bad shape so I pulled them and changed out the connectors also. only issue is the sensor on the passenger side head. cant figure out what it is. ive read that it is an EFE sensor ( early fuel evaporation) but at auto parts store they looked at sensor pics and said its for the electric fan on front side of radiator. any ideas?

Re: TBI 454 running rich
 

Rebuilt TBI injecters are not to pricey if there slobering but i would said the o2 sensior would have been a prime suspect. Or if they would have put a chip in with low temp stat fooling it into warm up mode all the time.

Re: TBI 454 running rich
 

I can't help but think the ECU is running the engine in "limp home mode", which is very rich to ensure the engine isn't going to go lean. This could be caused by:
1) Dead O2 sensor (I wonder if the wire to the sensor is intact with your new sensor)
2) Dead coolant sensor
3) Not limp home, but if the coolant sensor indicated cold or the engine actually was cold (bad thermostat)
4) I'm not sure if the throttle position sensor can trigger this mode or not.

Anyway, good luck!

Re: TBI 454 running rich
 

thanks for the responses. I never knew that these trucks could
go into limp mode. just a little more info. since changing all of these sensors I haven't yet driven or started the truck. im waiting on what I believe is the electric fan switch on the passenger side head. also which is kind of funny. I had to run flat tires just to get the truck in the garage. so im in the process of lowering the truck now. if I can ill post some pics. pretty comical and sadly not the first time I had to do this with a truck to get it in a garage.

Re: TBI 454 running rich
 

One thing that you may want to look at, has the truck had different exhaust put on it? More free flowing? if so you may want to put a 3 wire O2 sensor on it.