running lean. please help

[demon858585]

Need help. Truck is running extremely lean. With a little help it will start and stay running for a few minutes but then it starts bogging down and dying out. It cuts off as soon as I put it in drive. In the last week I have installed new: fuel pump & filter, injectors, rebuilt tbi, check fuses, and bypassed egr valve (egr hasn't worked for 2 years). I just sucked out the rest of the fuel. I tried to change a o2 sensor but my exhaust doesn't have 1. My next steps are map sensor, knock sensor, then computer. Any thoughts before I go completely bankrupt?
1989 gmc 5.7 350 tbi 4x4 burb

 

[1997chevydriver]

It's in the ds exhaust manifold.

How can you tell it's running lean? Did you check for vac leaks?

 

[98sierra4x4]

Your problem might be that you don't have an o2 sencor


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[demon858585]

its backfiring and dying out like its no getting enough fuel. I check for vac leaks by spraying parts cleaner also I rebuilt the tbi just incase. no leaks. Im thinking map sensor but I cant install new one until tomorrow . what sensors can make it run lean?

 

[demon858585]

ran for 2 years without o2 sensor. this problem just started last week.

 

[SCOTTYINWV]

I would be leaning more towards running too rich If it's backfiring imo. Too much fuel not being burnt properly. Does it have a check engine light?

Did it just start at random? Timing?

 

[demon858585]

no check engine light, the previous owner must have disabled it somehow .
it randomly started sputtering and died out about two weeks ago while driving on the freeway.
timing may be an issue but why would the timing go retarded out of nowhere?
don't have timing light to check the timing yet.

thanks for your help.

 

[96-1500]

Does the check engine light work? As in, turn key on when truck not running, does it light up?

If yes, and there's definitely no code, and no o2 sensor in the truck, somebody has been messing with it. TBI requires input from the o2 to work properly, it will run without it, but not well.

I wouldn't rule out timing as a problem, but I would try to get to the bottom of this lack of o2 thing first. Is there a wire for one? Should be around the drivers side exhaust manifold where the sensor "should" be.

From your description, I'm guessing somebody threw on a manifold from a carb'd truck with no sensor bung.

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