Bad performance

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crrios

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Hey everyones!! I have a 1993 GMC Suburban 5.7 lts 4 WD and i cant get any better than 5 miles per gallon, i replaced the wires, the fuel injector seals, fuel filter, plugs and cleaned the TBI, put the timming on 8 degrees BTDC the oxigen sensor are moving slow between 0.400 & 0.700 but when you press WOT has black smoke and feels like has much fuel......it doesnt ny fault codes..

If i moves the timming to 35º BTDC has a better performance (12 miles per gallon)....

Querstions: Could be valves lifters issue???

Anyones can give me a better some ideas...?

Sorry about my English
 
crrios said:
Hey everyones!! I have a 1993 GMC Suburban 5.7 lts 4 WD and i cant get any better than 5 miles per gallon, i replaced the wires, the fuel injector seals, fuel filter, plugs and cleaned the TBI, put the timming on 8 degrees BTDC the oxigen sensor are moving slow between 0.400 & 0.700 but when you press WOT has black smoke and feels like has much fuel......it doesnt ny fault codes..

If i moves the timming to 35º BTDC has a better performance (12 miles per gallon)....

Querstions: Could be valves lifters issue???

Anyones can give me a better some ideas...?

Sorry about my English
Click to expand...

Replace your TBS and the MAP sensor. Also give your Suburban a http://www.seafoamsales.com/ treatment. Just make sure your in a well ventilated area like out side a garage. :D

Start with these few simple things and keep us posted. ;)

Molson02536
 
well these temp sensors were know to go -40 so check the coolant temp sensor There cheep. Now the map and tps sensor would put the check engine light on. If you have no check engine light don't waste your money throwing partsd at it. If you can get a data stream it will be a easy problem to fix.
 
happy 2011 said:
well these temp sensors were know to go -40 so check the coolant temp sensor There cheep. Now the map and tps sensor would put the check engine light on. If you have no check engine light don't waste your money throwing partsd at it. If you can get a data stream it will be a easy problem to fix.
Click to expand...

OBD1 system will not put a check engine light on TPS and MAP sensors when dirty unless it's not giving out any reading at all or its way out of it's programmed perimeter. But hey what do i know, i only drive a tour bus now and got away from tuning up street cars for a living lol.

Good luck and keep us all posted. Be glad to know you got your Suburban running 100% again soon.

Molson02536
 
Its looks like i have been doing the things in the wrong way!!!
Who can explain me wich wire must be disconected to set timing?
In this engine must be adjusted to 0??
Let me fix the timimng first ant then i will let you konw
Thnaks for your support!
THis is the links that shows the distribuitor
http://easyautodiagnostics.com/gm_icm_dist/modulo_encendido_distribuidor_1.php
 
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