s10 problem what to do next

[mac12957]

have 1997 chevy s10 pickup and had not wanted to start when engine was hot. wait 20 minutes and starts fine. always started fine cold. replaced plugs wires cap and rotor, no difference. 2 weeks later had no start situation. had nice blue spark on all cylinders. coil tested weak so I replaced. tested ignition module was ok. fuel pressure tested 53 psi(key on not running) but pressure slowly dropped off. changed fuel pressure regulator cleaned top of intake under plennum replaced upper intake gaskets and now truck starts nice. however after started idles rough and stumbles when leaving stop light. has all kinds of power while driving down road. I get code p0141 (oxygen sensor bank1 sensor3). wiring checks ok so I replace sensor, code goes off and stays off. I drive truck and after 15 miles loses power and acts like cat. converter or muffler is plugged. I get home and replace cat converter and muffler (has not done this again). still runs roughand stumbles when taking off from stop. I clean maf sensor, clean iat sensor,and clean egr valve,no change in performance. next I use multimeter and check tps, map sensor, and iag valve. all check out ok. I now am also getting p0171 and p0174. I check fuel pressure again and is still at 53 psi(not running) and droppes to48 psi at idle.I am still getting a drop in fuel pressure when tested. Is pump bad or spider injector bad or something else bad? running out of ideas! please help!

[MT-2500]

Originally Posted by mac12957

have 1997 chevy s10 pickup and had not wanted to start when engine was hot. wait 20 minutes and starts fine. always started fine cold. replaced plugs wires cap and rotor, no difference. 2 weeks later had no start situation. had nice blue spark on all cylinders. coil tested weak so I replaced. tested ignition module was ok. fuel pressure tested 53 psi(key on not running) but pressure slowly dropped off. changed fuel pressure regulator cleaned top of intake under plennum replaced upper intake gaskets and now truck starts nice. however after started idles rough and stumbles when leaving stop light. has all kinds of power while driving down road. I get code p0141 (oxygen sensor bank1 sensor3). wiring checks ok so I replace sensor, code goes off and stays off. I drive truck and after 15 miles loses power and acts like cat. converter or muffler is plugged. I get home and replace cat converter and muffler (has not done this again). still runs roughand stumbles when taking off from stop. I clean maf sensor, clean iat sensor,and clean egr valve,no change in performance. next I use multimeter and check tps, map sensor, and iag valve. all check out ok. I now am also getting p0171 and p0174. I check fuel pressure again and is still at 53 psi(not running) and droppes to48 psi at idle.I am still getting a drop in fuel pressure when tested. Is pump bad or spider injector bad or something else bad? running out of ideas! please help!

Fuel pump????

Pump needs 60/66 lbs pressure.
4.3 v6 CSI
64 engine cranking.

56/62 SFI 4.3.
59-60 engine cranking.

[old_master]

Low fuel pressure and excessive leakdown is your problem. Most likely a weak fuel pump and leaky check valve in the pump. Key ON, engine OFF, fuel pump running, fuel pressure must be, (as MT stated) 60psi to 66psi and must remain above 55psi for 10 minutes after the pump shuts off. Stay away from aftermarket fuel pumps, use AC Delco or Delphi only.