Lean acceleration per O2 readings (again)
 

93 suburban, 350 TBI, well maintained. Just started to fall flat on it's face on acceleration. Unplugged the EGR since I suspected the new one had failed, it improved the performance but still no power, just doesn't try to stall out now.

Hooked up the computer and once I crack the throttle the O2 sensor readings bottom out. I mean BOTTOM out and it doesn't improve till I back off the throttle and this it come way up bounced back and forth normally. O2 counts are 30 up to 60.

I had something similar once before and finally found clogged injector. I suspect this is the cause again but what else could cause this? I want to check all the components first.

Re: Lean acceleration per O2 readings (again)
 

I would test the fuel pressure during acceleration while the problem is happening.

How old is the fuel filter?

Re: Lean acceleration per O2 readings (again)
 

I just had a similar problem on my 98 4.3. Smooth idle and and reved up smoothly in neutral but sluggish ecceleration. I had a bad cat. I drilled a 4" hole with a hole saw,emptied the cat and welded the cutout back in. Runs like new again. Mine had a rattle sound coming from the cat that was getting louder,it turns out the piece of ceramic to the rear was broken and turned sideways so exaust didn't flow through it and it partially blocked the pipe.

Re: Lean acceleration per O2 readings (again)
 

Fuel filter is probably 2 years old? But I did think about that last night. I have the inline gage but obviously can't see it when driving. The injectors are only a couple of years old too.

Cat was removed before I got it.

Re: Lean acceleration per O2 readings (again)
 

Low fuel pressure. 9 PSI at idle and drops to 6 when I rev the engine. Last time I checked it, it only dropped about .5-1 lbs when I reved the engine. So it is fuel delivery. I will start with the filter since it is easiest.

Also the 40 gallon tank is near full so I need to burn some off before I try to drop it. Does the suburban have an access to the tank in the cabin??

Re: Lean acceleration per O2 readings (again)
 

spec is 9-13, it should be 12-13.

Pinch the return line and see if it peaks. If it reaches 13+ PSI, your problem is in the regulator/throttle body. If it stays low, it is the pump(or the rubber hose in the tank may be split)

There is not an access panel to reach the pump. The tank needs dropped.

Re: Lean acceleration per O2 readings (again)
 

New Delco filter and same results. Pinched the line and no change. Darn it.

Now the question is whether to replace the pump while I have the tank out, if it turns out to be the rubber line? No idea if this is the original pump or not.

Re: Lean acceleration per O2 readings (again)
 

cheap insurance to just replace the whole module while you've got the tank down!

Re: Lean acceleration per O2 readings (again)
 

Which line did you pinch?

Re: Lean acceleration per O2 readings (again)
 

Return.

Re: Lean acceleration per O2 readings (again)
 

Pump time

Re: Lean acceleration per O2 readings (again)
 

One sitting in my back seat. Just filled up the 40 gallon tank so trying to wait till I burn most of that off.

Re: Lean acceleration per O2 readings (again)
 

what a difference 3-3.5 lbs for fuel pressure makes!
What a pain in the but putting the tank back in place was!

Loving the way it runs again. Fixed all this little annoying things it was doing.