350 TBI

[fredflinstone]

Hey guys,

Got a 350 TBI engine in a 87 silverado. Engine worked fine before I laid her up 6 months ago.

Now she back fires up through the intake of the TBI.

Engine starts fine. Runs fine all through the rpm range while in park. Problem is when i am running along and step on the gas, it is almost like a back fire up through the intake of the TBI. not sure if i am using the correct term with "backfire" but that's all i got.

I have replaced both injectors, TB position sensor, idle air valve. And the truck still does the "backfire" through the intake of the TBI when i accelerate

 

[Vbb199]

Fuel pump?

 

[Vbb199]

Also, when you replaced the IAC, did you recalibrate it ?

 

[fredflinstone]

I turned on the ignition for 5 seconds and did not start. Then I turned off, then started up truck. That's how i calibrated the IAC.

 

[Vbb199]

Should be ok i think.

But that fuel pump? How old is it?

 

[fredflinstone]

She is only 5 years old with only about 20 K miles on her

 

[gmbellew]

this is what the emmisions/drivability manual says. check the reference library for more details.

You must be registered for see images attach

 

[Catbox]

Ours would backfire randomly when we changed out some of the parts trying to get through DEQ.

Turns out the new coil we installed was not so good.
It caused all kinds of drivability issues.

Put the known old one back and we are back in business.

 

[Vbb199]

Story time:

I had purchased a brand new acdelco fuel pump, i had it for approx 1 year, and it never had any miles on it it was only used for fire up's of a motor, in which the motor would run for maybe 30 minutes max here and there.

I placed said new pump in a build of mine that was intended to be ran on the road, all was well for a short period (less than a couple miles of driving) and all of a sudden one day i started getting backfiring thru the throttle body, constantly, under any engine load. In park, it would be fine as long as i "eased" into the gas pedal, any sudden wicks of the throttle it sounded like it was sucking air, and and would bog the motor , then ultimately, backfire.

I checked ignition coil, and replaced it with a good known one , nothing, checked timing, nothing, Bought a new ignition module, nothing. Replaced the plugs, nothing. Verified i had spark on all 8 cylinders, so i finally just checked fuel pressure, i found it was below the required amount. Im not saying this instance is a fuel pump, but some pumps have varying quality, and the even cheaper ones from the parts store are even worse.
Ive learned the name acdelco doesnt mean ****. That one died at 1 year the exact replacement came with junk service parts.

 

[Octane]

I use a good gas stabilizer and never let gas sit for 6 months anyway.