S10 4.3l won't accelerate

[cobey]

Timing chain is another possibility.

Timing chain is another possibility.

I was thinking that maybe.

 

[paragonbuilder]

Does it idle "perfect" or is it labored or rough in any way? If you unplug a sensor while it's running it will typically stall. If you cycle the key it should restart(ses lamp will be on) and run. It may not run perfectly but atleast run. If the unplugged part was giving an erroneous resding, it should run better than when it was plugged in. MAF are notoriously junk on those vehicles. TPS could be wacking out too. IAT reading and ECT readings could off and messing with fuel trims too.

If you very carefully ease the throttle open does it instantly stall or will it pick up some rpms?


Dumb question, did you just get gas? How cold is it in your neck of the woods and is it parked outside? Could be a partially frozen/ restricted fuel line. Could be letting enough through to idle but no more.

Idles perfect til I touch the throttle. Occasionally I can get it just over 1k if I nurse the throttle, but mostly it instantly bogs. Then runs rough for 10 sec or do before evening out. This happened in April, ive revisited it a couple times this summer and then again today. It is in my heated garage. It's getting towards empty but ran good on this tank of fuel until that one morning, now this...
It's got 60 psi at idle.

 

[Cutforfun]

Mine had good pressure at idle also, ck it when you are revving it up.

 

[dall]

60 isnt enough at idle for fuel pressure need to be above 75 at idle

 

[jake wells]

has it ever had the fuel filter changed?

 

[Milkman31]

Check the distributor drive gear for wear. I had a 4.3 that did damn near the same thing.

Best answer!! I just changed one in a 7.4 at work. The 4.3,5.7,7.4 all use the same distributor. This one had three teeth wore off and the rest were very thin.

 

[jmssaws]

4.3 still have a distributor in 99?

I know 99 was the first year for the 5.3 6.0
Ls motors and they don't have distributors.

 

[junkman]

4.3 still have a distributor in 99?

I know 99 was the first year for the 5.3 6.0
Ls motors and they don't have distributors.

The 4.3 still has dist ignition.

I would drop the tank and look for beads of water in it,maybe replace the fuel pump also. You are starving for fuel somewhere. I tow a lot of gm rigs to shops with bad pumps so it is a common thing to fail.

 

[DELETED (Struggle)]

Your not getting timing advance it would seem. Even though the distributer has no mechanical advance the electrics in it may have failed causing no advance in timing. So if you can change it out with a known good one might be a good place to start.

Also check fuel pressure running and possibly with another fuel gauge to verify proper pressure running. Also they are known to have fuel pressure regulated issues. Fuel pump failures are common on those truck and aftermarket fuel pumps can be problematic even though they may have lifetime warranties.


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[drf256]

Start simple before you go nuts. Pull all six plugs. Look at the color. Do a compression test on all cylinders.

Pull valve covers. Turn engine over and watch for any freaky abnormality.

They should have a timing chain. The 4.8 is like a 350 Chevy with 2 cylinders lopped off. If it popped, it shouldn't run at all. Watch the distributed rotate as well with the cap off.

Dan, I went crazy on my brothers for a similar issue. Finally did a comp test and notice one entire bank of plugs were leaner. Was the intake manifold leaking on one side.

Could certainly be fuel pressure as well.

 

[Nitehawk55]

If it's running smoothly at idle with no misfire and as you describe is just stalling out when you try to throttle up then runs rough for a bit it sure sounds like fuel pump / fuel starving to me .
You mention it's low on gas , throw 5 gallons in it and see if that makes a difference .

 

[Dub11]

My buddys 01 need new computers.

 

[paragonbuilder]

has it ever had the fuel filter changed?

Yes twice since I got it. And during this ordeal.

 

[paragonbuilder]

Mine had good pressure at idle also, ck it when you are revving it up.

This gauge has a pressure release, I think so it can hold the high reading like a compression gauge. How do I check it while I'm trying to rev it? I've got a sec or two max before it dies if I try to rev it...

 

[paragonbuilder]

60 isnt enough at idle for fuel pressure need to be above 75 at idle

The book says 60-66. But it needs to maintain it during accel, and I'm not sure how to check it. See above post.
I know when I checked it when I put the new injectors in it was 60 at idle...

 

[paragonbuilder]

The 4.3 still has dist ignition.

I would drop the tank and look for beads of water in it,maybe replace the fuel pump also. You are starving for fuel somewhere. I tow a lot of gm rigs to shops with bad pumps so it is a common thing to fail.

This is what I keep coming back to...

 

[paragonbuilder]

Your not getting timing advance it would seem. Even though the distributer has no mechanical advance the electrics in it may have failed causing no advance in timing. So if you can change it out with a known good one might be a good place to start.

Also check fuel pressure running and possibly with another fuel gauge to verify proper pressure running. Also they are known to have fuel pressure regulated issues. Fuel pump failures are common on those truck and aftermarket fuel pumps can be problematic even though they may have lifetime warranties.


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I'm going to pull the dist and see.

 

[paragonbuilder]

I know the intake manifold gaskets are issues on these... How do I test for it?
Does it have the symptoms I'm describing?

 

[paragonbuilder]

If it's running smoothly at idle with no misfire and as you describe is just stalling out when you try to throttle up then runs rough for a bit it sure sounds like fuel pump / fuel starving to me .
You mention it's low on gas , throw 5 gallons in it and see if that makes a difference .

I did that. And changed the filter. While the filter was off I ran the pump and collected the fuel. I didn't see any water...

 

[paragonbuilder]

My buddys 01 need new computers.

How would I know this?