S10 4.3l won't accelerate

[paragonbuilder]

It'll never run right with plugs that fouled. If you drop below 60 psi then injectors may. Or spray properly causing it to foul plugs. Psi should raise up at least 5 psi or maybe re when you throttle it. Has it ever had an intake gasket replaced. If answer is no it needs to be replaced. They all go bad on the 4.3 and it can run lean from sucking on bottom side of intake


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I'm not sure if it's been replaced. I bought the truck last Oct.

 

[junkman]

Running junkyard gas over the years ,i have had a few rigs get some water dumped in them from it ,for some reason the water in the fuel makes the black smoke in efi rigs ,maybe the computer is compensating for the lean condition ?? I have got them to clear up by taking the main fuel line off ,and blowing back toward the tank with a rubber tipped blow gun ,It is usually a temporary fix till the tank gets cleaned out though ,may crack the fuel cap if do this ,the tank will expand and possibly blow the vent off the top of the tank if the air has no where to go .

 

[paragonbuilder]

It'll never run right with plugs that fouled. If you drop below 60 psi then injectors may. Or spray properly causing it to foul plugs. Psi should raise up at least 5 psi or maybe re when you throttle it. Has it ever had an intake gasket replaced. If answer is no it needs to be replaced. They all go bad on the 4.3 and it can run lean from sucking on bottom side of intake


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Is there a way to test for intake gasket?

 

[junkman]

Is there a way to test for intake gasket?

Put your hand over the air intake when it is running ,if you can choke the engine and kill it ,no air leak ,if it stays running choked down ,has a leak .

 

[paragonbuilder]

Put your hand over the air intake when it is running ,if you can choke the engine and kill it ,no air leak ,if it stays running choked down ,has a leak .

That would be a massive leak, no?

 

[junkman]

That would be a massive leak, no?

The way your plugs are so black ,i would not think an air leak ,more a sensor or computer compensating for fuel starvation /bad fuel delivery .

 

[Canadian farm boy]

Dan, this is a 4.3L vortec engine correct?

 

[paragonbuilder]

Dan, this is a 4.3L vortec engine correct?

Yes

 

[Canadian farm boy]

I used to have 5.0L vortec. IIRC the fuel pressure should be 60-64psi at idle and when you rev the engine it should increase approximately 5psi.
I had a fuel pump go out on my 5L vortec. At idle my fuel pressure was 62psi but when I reved the engine it would increase only 1-2psi and then drop off to around 50psi. My engine would idle all day but made no power and was nearly impossible to drive. A new fuel pump fixed my problem.
The vortec engines are very sensitive to fuel pressure.

 

[Canadian farm boy]

I have a manual around here somewhere covers the vortec engines. I'll see if I can find it

 

[Stihlbro]

Is there a way to test for intake gasket?

Most of those intake gaskets leak at the coolant passages. You should see signs of antifreeze or deposits at the corners. The egr valves are know to get carbon tracked and stick, which creates a vacuum leak. Symptoms are stalling, low low idle and a hard brake pedal(loosing vacuum to brake booster). You have blocked that off, so that is eliminated. If the coolant temp sensor is giving a skewed reading, in this case be telling the engine it super cold and it needs more fuel. It will enriched the fuel demand substantially but as the engine warms up it won't seem as bad. Engine should still rev up.

It takes more fuel pressure to get the engine to start but once running and does not require as much. The poppet nozzles will pop out of the intake which will fill the lower intake. If you suspect fuel pressure, one easy check is to pinch off the return line to the tank to try to keep the volume at the injector/poppet nozzles

If you lived closer, I would load up and come help.

 

[paragonbuilder]

I used to have 5.0L vortec. IIRC the fuel pressure should be 60-64psi at idle and when you rev the engine it should increase approximately 5psi.
I had a fuel pump go out on my 5L vortec. At idle my fuel pressure was 62psi but when I reved the engine it would increase only 1-2psi and then drop off to around 50psi. My engine would idle all day but made no power and was nearly impossible to drive. A new fuel pump fixed my problem.
The vortec engines are very sensitive to fuel pressure.

Kinda what it's doing.

 

[Canadian farm boy]

In my experience 9 out of 10 fuel pumps will just quit working all together but there is always that 1 that will still sorta work. I'm leaning towards you have that 1 just like I did.

 

[paragonbuilder]

Most of those intake gaskets leak at the coolant passages. You should see signs of antifreeze or deposits at the corners. The egr valves are know to get carbon tracked and stick, which creates a vacuum leak. Symptoms are stalling, low low idle and a hard brake pedal(loosing vacuum to brake booster). You have blocked that off, so that is eliminated. If the coolant temp sensor is giving a skewed reading, in this case be telling the engine it super cold and it needs more fuel. It will enriched the fuel demand substantially but as the engine warms up it won't seem as bad. Engine should still rev up.

It takes more fuel pressure to get the engine to start but once running and does not require as much. The poppet nozzles will pop out of the intake which will fill the lower intake. If you suspect fuel pressure, one easy check is to pinch off the return line to the tank to try to keep the volume at the injector/poppet nozzles

If you lived closer, I would load up and come help.

I'll try pinching the return line. That's a good idea. Thanks Joey.

 

[paragonbuilder]

In my experience 9 out of 10 fuel pumps will just quit working all together but there is always that 1 that will still sorta work. I'm leaning towards you have that 1 just like I did.

That's why I'm reluctant to spend $250 on a pump. I've always seen them puke out completely...

 

[paragonbuilder]

I'll try joeys idea of pinching the return and see what happens

 

[Stihlbro]

Pull the coil wire at the coil, any white corrosion? Look at the coil mounting is there white powdery spots on the rivets?

 

[paragonbuilder]

Pull the coil wire at the coil, any white corrosion? Look at the coil mounting is there white powdery spots on the rivets?

I had white corrosion on the cap and rotor points...

 

[Stihlbro]

I've seen it on the coil connection and do wacky things like your experiencing.

 

[paragonbuilder]

Ill be home in a half hour. Can start looking again.