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88 TBI Running Rrich

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z3ro725

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I have an 88 TBI 5.7L Blazer that smells like it's running very rich and is only getting 11 MPG. Is that normal for TBI? i thought they got better then that.


new fuel pressure regulator

Coolant temp sensor works properly

no check engine light and no codes found

has 93 suburban engine recently installed by me but original TBI unit and had same problem with old motor, i only replaced it because the block had a freeze crack

mechanic doesn't even know what the problem is

Any suggestions?
 
z3ro725 said:
no check engine light and no codes found
Click to expand...

Actually you need to replace that bulb then... it should light up when you first turn on the key and you should always get at least two codes when you check them, 11 and 55.
 
mine does the same thing. one of my problems is no cat on it. i just replaced the 02 sensor and it got a little better
 
completly stock truck with no lift and stock tire size

has new o2 sensor

light does work properly and yes the normal code comes up when it's not running.

used to have a code for the o2 sensor but i replaced it and no codes have come up since
 
Very good visual inspection of the engine bay has been done? Spark plugs, wires, all wiring/connectors, and especially vacuum lines?
 
did you buy this truck off of somebody or are you the original owner?
makes me wonder if it has a cat under it if it was gutted.
 
It should only flash a code 12 if there are no codes stored.

When I got my Suburban it was lacking in power and the milage was crap, even for a burban. It was because the timing was set back way too far. Ran fine otherwise.
 
plugs, wires, cap, and rotor are all new.

checked, double checked, rechecked, and then checked lines and connections again.

timing is set dead nuts on 0 with the conector unpluged

there is only that one code when the engine is not running, which is supposed to be there.

I am not the origional owner and the cat is still there. it's the old style bead type but it's there

could it be the computer? or some moduel under the hood?
 
i swaped out the map senspr on mine only cause i had a spare. it didnt change anything. im thinking about looking at the egr next on mine
 
Mine is exactly the same. Smells fat, gets $hit mileage (10 or so). I'm not going to put money into fixing it since I will be swapping in a diesel.
 
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Mine is the same, but I get 9 mpg. I've owned it for about 5 years and it has always gotten 9 mpg. It's had a new engine put in, the tbi rebuilt a new o2 sensor, new knock sensor, full tune up, had stock cat, it ran away. It's been lifted, changed from 3.73 10b to 4.10 14bff and from 235's to 33" tires. IT GETS 9 MPG, no mater what, I've accepted it. :dunno:
 
My truck with an LO5, sm465, 3.73's, and 36 tsls get about 15mpg.

I would quadruple check for vacuum leaks, change plugs, wires, rotor, cap, coil. Get delco plugs, streetfire, accel, or MSD for the rest. When I switched from stock garbage to MSD coil, cap and rotor I picked up about 2mpgs and my truck wouldnt bog down when idled. Dont forget the good ol PCV valve.

Also grab a TB spacer and injector pod spacer worth another 1-1.5 mpg. Also an open element or dual snorkel will help.

Changing to a heated 3 or 4 wire o2 sensor from a 4.3 s10 will also yield some better mpg's when you first take off in the morning and everything is still cold.

Also its in your best intrest to advance your timing as far as it will comfortably go on which ever octane you choose to use. This will give you a little more power which means less foot in the gas to get moving.



AND the biggest tip of all. DRIVE LIKE AN OLD WOMAN! It gets my 20mpgs in my 305 monte...
 
z3ro725 said:
could it be the computer? or some moduel under the hood?
Click to expand...

It could be, along with a million other things. Don't throw parts at it, that gets expensive fast. :)

Those pellet style cats are a terrible design, you can test backpressure at the O2 sensor port with the proper gauge to see.
 
Stomis said:
Also its in your best intrest to advance your timing as far as it will comfortably go on which ever octane you choose to use. This will give you a little more power which means less foot in the gas to get moving.
Click to expand...

Quoted for truth. Most seem willing to run in the 6*-10* range on regular gas.
 
thank you all for the advice very helpful, I will advance that timing as soon as I get a chance.

I also have a fairly new 3" downpipe and new style cat and flowmaster from another blazer that got junked so that old nasty cat will be going
 
Stomis said:
My truck with an LO5, sm465, 3.73's, and 36 tsls get about 15mpg.

Also grab a TB spacer and injector pod spacer worth another 1-1.5 mpg. Also an open element or dual snorkel will help.
Click to expand...

where is a good place to get these?
 
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