1994 chevy s10 blazer

[chrisfrom nj]

i just picked up a 1994 chevy s10 blazer the truck runs great when its cold as it warms up the truck stumbles when you go up hills or when you step on the gas theres no check engine light on i checked for codes i didnt get any can someone please help

[Green_Phoenix_LT1]

Sounds like an issue with either the spider injection system or the fuel pump.

[chrisfrom nj]

Originally Posted by Green_Phoenix_LT1

Sounds like an issue with either the spider injection system or the fuel pump.

thanks im going to check the fuel pressure hopefully its the pump

[alamantia]

Why would fuel pressure change when the motor warms up? Check the EGR

[Iroc-z86]

i dont think its fuel pressure related. it could be o2, map, or if it has it maf. my jeep was running really bad without a cel so i thought i yanked the wires out of my o2 when i was on the trail. they looked good, but the upstream o2 was literally in 2 pieces from age sure enough after i touched it cel came on. replaced the sensor and its been fine ever since.

[chrisfrom nj]

Originally Posted by alamantia

Why would fuel pressure change when the motor warms up? Check the EGR

the truck has a new egr in it

Originally Posted by Iroc-z86

i dont think its fuel pressure related. it could be o2, map, or if it has it maf. my jeep was running really bad without a cel so i thought i yanked the wires out of my o2 when i was on the trail. they looked good, but the upstream o2 was literally in 2 pieces from age sure enough after i touched it cel came on. replaced the sensor and its been fine ever since.

thanks im going to check the 02

[chrisfrom nj]

fuel pressure is good, the egr is new, new plugs ,wires, cap and rotor, new fuel filter, ignition control mod, checked the coil, no check engine light on it i unpluged the o2 and drove thei dont know why the check engine light didnt come on feels like the cat is clogged

[91chevywt]

It's worth checking the cat out...bad fuel spiders can cause rich conditions that will wipe out the catalytic converter in a hurry. Tap on the outsize of it with a rubber mallet and see if it rattles.

You say fuel pressure is good...you didn't check it only by squirting a little fuel out of the test port right? The CPI motors are very sensitive to fuel pressure, as they require pretty high pressures to run correctly. I forget what it was exactly though...but i'm sure you could find out online.

You may have a leaking poppet in the fuel spider or a leaking fuel line under the upper-intake manifold. Either of these issues will allow the truck to start very easily and idle or warm up fine, since the engine can handle the extra fuel, but once it warms up it'll have no power cuz it's too rich.

It would be worth it to look at the o2 sensor as well. If you have over 100k on the truck and it still has the stock sensor, it would be worth it to replace. I think theyre like $25-$30. But investigating the fuel spider is the best thing to do since they are so troublesome

[chrisfrom nj]

Originally Posted by 91chevywt

It's worth checking the cat out...bad fuel spiders can cause rich conditions that will wipe out the catalytic converter in a hurry. Tap on the outsize of it with a rubber mallet and see if it rattles.

You say fuel pressure is good...you didn't check it only by squirting a little fuel out of the test port right? The CPI motors are very sensitive to fuel pressure, as they require pretty high pressures to run correctly. I forget what it was exactly though...but i'm sure you could find out online.

You may have a leaking poppet in the fuel spider or a leaking fuel line under the upper-intake manifold. Either of these issues will allow the truck to start very easily and idle or warm up fine, since the engine can handle the extra fuel, but once it warms up it'll have no power cuz it's too rich.

It would be worth it to look at the o2 sensor as well. If you have over 100k on the truck and it still has the stock sensor, it would be worth it to replace. I think theyre like $25-$30. But investigating the fuel spider is the best thing to do since they are so troublesome

im going to check the cat tomorrow when i have it on the lift i pulled off the vortec cover and looked at the injector everything looked the same it was black not clean i checked the fuel pressure with the fuel pressure gauge it said 55 at idle and it goes up when you rev it the think that gets me is if its 55 when you turn the key on without starting it then it drops to 15 when the pump shuts off im getting a new o2 tomorrow the truck has 99,000 miles

[91chevywt]

The pressure dropping to 15psi after you shut it off indicates some type of leak somewhere. It may mean a poppet is stuck open on the fuel spider. You might be able to clean it out by running fuel injector cleaner through it for a while if that's what it is. It could be clogged with carbon. A bad poppet will have a poor spray pattern and cause it to run almost like it's down a cylinder

[chrisfrom nj]

Originally Posted by 91chevywt

The pressure dropping to 15psi after you shut it off indicates some type of leak somewhere. It may mean a poppet is stuck open on the fuel spider. You might be able to clean it out by running fuel injector cleaner through it for a while if that's what it is. It could be clogged with carbon. A bad poppet will have a poor spray pattern and cause it to run almost like it's down a cylinder

thanks for the info im going to pick up some sea foam tonight and run it im about to order a new spider injector for it im going to use the truck for plowing i dont need it to break down on me during the snow season

[chrisfrom nj]

i sea foamed it it didnt wok im getting a injector for it tomorrow