1991 4x4 S-10 4.3 surging loping

Hi everyone,
I have a 1991 S-10 4x4 4.3 tbi, got this truck from my father it sat for 3 years with fuel in the tank, when started idle is good at first then it will idle down and sputter then come back up. levels out after a few minutes but still is rough, when driving at crusing speed surges or lopes, also at times will act like it has no fuel. but at times runs great.

Parts and things I have checked or replaced

fuel tank
sending unit
pump
filters
injectors
fuel metering valve at throttle body
rotor cap, rotor, plugs and wires

I am out of ideas any help would be greatly appreciated
Thanks

What is the fuel pressure when acting up?
Have you checked fuel and air filter?
Any check engine lights or codes?
Any bad vacumn lines or vacumn leaks?
Good Ac delco plugs?
Base timing set right?
Has EGR valve been checked?
PCV valve good AC delco?
Have you checked the base gasket under TBI.?

Hi MT
Thanks for the reply,
fuel pressure do not have a way to test will have to take to a shop does have a new O Reily pump (I know should have bought better)
Fuel and air filters both new
No lights or codes
Have checked and replaced all vacuum lines that even looked like they might be bad
AC delco plugs w/ correct gap
Have not checked base timing don't really know how and do not have a timing light
EGR new
PCV valve new ac delco
Going to check the base gasket

Truck did pass AZ emissions and does act worse when taking corners.
Is there a tool I could rent from autozone to check fuel pump pressure?
also the truck sat for 3 years and my Dad tried to start it with the old gas in the tank, drained the tank used pea gravel and diesel to clean tank and finally gave in and bought new tank put in on the 23rd and at that time replaced the sending unit, in tank screen and chassis filter. when I first got it running ran a can of seafoam thru it. I was reading on here and think it could be the TPS as that seems to control all of the things that are acting up. Also I talked to my Dad yesterday he is 72 and his memory aint to good anymore and he told me it was starting to run bad when he parked it in 2008.

thanks for any advise as I really love this truck as it was my dads and now is mine.

Hi MT
Thanks for the reply,
fuel pressure do not have a way to test will have to take to a shop does have a new O Reily pump (I know should have bought better)
Fuel and air filters both new
No lights or codes
Have checked and replaced all vacuum lines that even looked like they might be bad
AC delco plugs w/ correct gap
Have not checked base timing don't really know how and do not have a timing light
EGR new
PCV valve new ac delco
Going to check the base gasket

Truck did pass AZ emissions and does act worse when taking corners.
Is there a tool I could rent from autozone to check fuel pump pressure?
also the truck sat for 3 years and my Dad tried to start it with the old gas in the tank, drained the tank used pea gravel and diesel to clean tank and finally gave in and bought new tank put in on the 23rd and at that time replaced the sending unit, in tank screen and chassis filter. when I first got it running ran a can of seafoam thru it. I was reading on here and think it could be the TPS as that seems to control all of the things that are acting up. Also I talked to my Dad yesterday he is 72 and his memory aint to good anymore and he told me it was starting to run bad when he parked it in 2008.

thanks for any advise as I really love this truck as it was my dads and now is mine.

Yes most AZ STORES RENT LOAN OR SELL FUEL PRESSURE TESTERS.
Also they can ckeck for codes while you are there.

Ok thans MT I swill go there and get one on my next day off which is Monday. I used the jumper method and did not get anything but a 12 Autozonw told me they could not pull codes from it, it was too old.

I would check for vacum leaks first for shure. Possibly a bad Idle air control solenoid.

Hey Everyone,
Ok here is the lastest update instead of checking the manifold gasket went and bought a rebuild kit for the throttle body, well basically had the manifold gasket in it and just redid all of the gaskets figured why not damn near evr=erything else is new why not that to also got a new TPS solinoid.
While trying to remove the old TPS one of the cheesy litlle aluminum bolts broke off could not get the old one ou but redrilled the hole out and got it mounted again... BUT when I did this the TPS is sitting a slight bit crooked.
Put everything back together took it for a test drive same thing, but today it is very bad almost stalling and then running awesome then back to shitty, would the TPS being off cause it to run worse I am thinking that if it is sensing the position of the throttle and it is off it is not getting a correct reading but I am not sure.
could not find a gas pressure gauge as of yet but I am on the hunt for one.
Any ideas???

Hey Everyone,
Ok here is the lastest update instead of checking the manifold gasket went and bought a rebuild kit for the throttle body, well basically had the manifold gasket in it and just redid all of the gaskets figured why not damn near evr=erything else is new why not that to also got a new TPS solinoid.
While trying to remove the old TPS one of the cheesy litlle aluminum bolts broke off could not get the old one ou but redrilled the hole out and got it mounted again... BUT when I did this the TPS is sitting a slight bit crooked.
Put everything back together took it for a test drive same thing, but today it is very bad almost stalling and then running awesome then back to shitty, would the TPS being off cause it to run worse I am thinking that if it is sensing the position of the throttle and it is off it is not getting a correct reading but I am not sure.
could not find a gas pressure gauge as of yet but I am on the hunt for one.
Any ideas???
Any check engine lights or codes?
Make sure the map sensor is working right.
Tps sensor can be checked with a good low voltage volt meter.
But would have to be way off to cause your problems.
Mae sure EGR valve is closing good like nom carbon balls under plunger.
Check dist gear for wear and side dist play and base timing.
Also check dist module and cap and rotor.
Watch for good hot spark to all plugs.
And get the fuel pressure checked.
Good Luck and let us know how it goes.

Hey everyone got lost but found my way back.
Took it to a shop had them do a pressure check they told me the fuel pump was not holding pressure under load, went and purchased a delphi pump dropped the tank yet again 3rd time get easier everytime :runaround:

checked everything when this was done replaced all the rubber lines from the tank to the chassis metal lines. still having the same problem.
they also said no codes but said it could be leaking somewhere when I remove the gas cap there is no pressure from the tank (no hissing )

any ideas I am trying to find a tbi to replace the one that has the broken screw where the TPS mounts it is not sitting level and I am not sure if that could be a problem
thanks for any ideas and help with this problem

Mike

Hey everyone got lost but found my way back.
Took it to a shop had them do a pressure check they told me the fuel pump was not holding pressure under load, went and purchased a delphi pump dropped the tank yet again 3rd time get easier everytime :runaround:

checked everything when this was done replaced all the rubber lines from the tank to the chassis metal lines. still having the same problem.
they also said no codes but said it could be leaking somewhere when I remove the gas cap there is no pressure from the tank (no hissing )

any ideas I am trying to find a tbi to replace the one that has the broken screw where the TPS mounts it is not sitting level and I am not sure if that could be a problem
thanks for any ideas and help with this problem

Mike
You need to do some proper testing.
As in post 8.

On TPS sensor run a voltage test on it and post back voltage readings.
At idle and an watch readings as you open throtle from idle slow to wide open