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454 t.b.i. running too rich?

J

James670X

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Nov 15, 2002
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Calgary, Alberta, Canada
My 1988 Chevrolet V30 with the 454 t.b.i. is running way too rich, especially at idle as it smokes brown + smells really gassy, so my question is what could cause this and how would I go about fixing it?
Edit: I've thoroughly cleaned the throttle body, replaced the 02 sensor, and have replaced the fuel filter along with a host of other general tune up items/procedures.
 
Dont forget the coolant temp sensor. (Located by thermostat housing) When they fail they usually tell the ECM that your engine is running cold even when it is warmed up. ECM thinks the engine is cold so it richens up the fuel mixture.
 
Thunder if the coolant temp. sensor was shot would my temp gauge inside the truck read low/not move at all?, if that is in fact the case there's no problem with the sensor as my truck warms up to a temp. of about 100 degrees C (I think).
 
No, CTS and temp sender for gauge are totally seperate.

If you can get access to a scanner (or have a laptop) you can check all of this stuff out yourself, just need winALDL (free) and build a cable (cheap) for the laptop option.
 
The most common problem would be the MAP sensor,
very easy to change also,
 
Yes you could keep replacing things till you find it. Or you could start by checking codes? Would be cheaper and faster than guessing and buying...
 
Make sure it has the FACTORY spec 195degree thremostat. If it doesnt get warm enough it will not go in closed loop (where it uses the O2 sensor to adjust fuel mixture). Also make usre there are not exhaust leaks between the head and O2. They will effect the mixtrue as well and re ignight the unburnt fuel in the manifolt. That makes the o2 think its lean and will make it run rich.
My other truck had a leak at the manifold and fixing it brought up the MPG by nearly 1mpg.
 
The vehicle will go closed loop much colder than 195*, I can't recall exacts, and I'm sure its different somewhat based on app, but I believe it is down near 125*.

Of course, that doesn't take into account the O2 sensor being COOLER based on engine temp, but I have no idea if engine temp makes a big enough difference on exhaust gas temps.

However, there really is no reason to run anything other than a 195* stat IMO, although plenty of people run 180*.
 
is there ayway to eliminate the 02 censor or make the truck think that the o2 is running correct? i remember when i put a multiport in a jeep yj there was a company that made a sensor that plugged into the o2 wire and you didnt need to run the rear o2 sensor but being that tbi is only 1 sensor and a 1 wire sensor at that is that at all possable?
 
4xrick said:
is there ayway to eliminate the 02 censor or make the truck think that the o2 is running correct? i remember when i put a multiport in a jeep yj there was a company that made a sensor that plugged into the o2 wire and you didnt need to run the rear o2 sensor but being that tbi is only 1 sensor and a 1 wire sensor at that is that at all possable?
Click to expand...

NO!

The O2 sensor reading continously changes based on how the engine is running, and therefore the ECM is constantly adjusting the fuel mixture based on that reading. It's not like the sensor just sends a constant signal.

The O2 simulators only work for the "rear" sensors that only function to monitor the catalytic converter.
 
Any updates on this? I have an 87 Burb with a 454 and it too is running rich. While towing my Blazer Yesterday, my buddy behind me mentioned he could smell the raw fuel when he got too close and this is at Highway speeds.:crazy:
 
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