Sudden engine surge pattern - BAD GAS??

[shawski]

Hi all,
I'm new to diagnosis on this recent rebuilt 22re on 330k mile truck.

I had a great day of errands yesterday, the truck ran great! I've got 150 miles on the fully rebuilt 22re. Last night I went to start up the truck and it didn't start, sounded like a fuel issue. After 3 tries it started, BUT it surges a consistent pattern and the idle is 500, instead of 750 where I had it set.

I did run the tank down to somewhere between 1-3 gallons left. I can't tell because my fuel gauge drops to empty when I'm at a half tank. (another thing I need to figure out)

So I bought the truck recently with a topped off tank of gas. But whatever gas was in there prior to top off was likely sitting for up to 1 year.

Is it possible that the surge is due to old gas/contaminents finally getting up to the fuel filter, or somewhere else?

I filled up the tank yesterday with premium to try to fix the problem, but it's still surging.

What should my next step be?

Thank you!!!

 

[mikesmith140]

It could be a few things. Initially, if you could test the fuel flow from the pump, that might tell you if you have a faulty pump. Also, how's the fuel filter? Is it now blocked from the possible crud at the bottom of the fuel tank? If it surges like this all the time, at least it's a consistent problem that you can keep trying to diagnose ... not an intermittent problem you're continually guessing at.

A relatively easy "throw parts at it" item is to get a new fuel filter and see what happens. If it clears up then it was either crud in the fuel tank or the filter finally got so bad after nearly 30 years that it was actually clogged up from doing it's job. While you have the fuel filter off, you might check how the fuel pump is working (does it give good pressure or is it just a trickle coming out of the fuel line).

 

[shawski]

It could be a few things. Initially, if you could test the fuel flow from the pump, that might tell you if you have a faulty pump. Also, how's the fuel filter? Is it now blocked from the possible crud at the bottom of the fuel tank? If it surges like this all the time, at least it's a consistent problem that you can keep trying to diagnose ... not an intermittent problem you're continually guessing at.

A relatively easy "throw parts at it" item is to get a new fuel filter and see what happens. If it clears up then it was either crud in the fuel tank or the filter finally got so bad after nearly 30 years that it was actually clogged up from doing it's job. While you have the fuel filter off, you might check how the fuel pump is working (does it give good pressure or is it just a trickle coming out of the fuel line).

New fuel filter 150 miles ago (2 weeks ago)... I have a new filter on order now to try as first diagnosis tomorrow after work.

 

[KTMRIDER]

New fuel filter 150 miles ago (2 weeks ago)... I have a new filter on order now to try as first diagnosis tomorrow after work.

check your idle adjustment screw, the little o ring that keeps it from backing out gets worn and can turn one way or the other on its own and will cause idle issue. also check all your vacuum lines

 

[shawski]

check your idle adjustment screw, the little o ring that keeps it from backing out gets worn and can turn one way or the other on its own and will cause idle issue. also check all your vacuum lines

Idle screw is solid, I have it marked where it was last set.

Vacuum lines was the first thing I checked with the surging occurred. These all are in place.

 

[shawski]

While you have the fuel filter off, you might check how the fuel pump is working (does it give good pressure or is it just a trickle coming out of the fuel line).

I'll try this test, but would you mind sharing with me how to do this once the filter is off?

 

[KTMRIDER]

does it run ok otherwise? as in once you give it some throttle will it
run?

 

[shawski]

does it run ok otherwise? as in once you give it some throttle will it
run?

It "runs", but the entire truck is shaky, no matter what gear. It smooths out when RPMS hit 2300+'ish (highway speeds). Low RPMs and low speeds it feel like it's going to die, but it doesn't, it stays around 500 rpms resting

 

[flyinhawaiian01]

this may sound crazy, but can you rotate the distributor right now? Sure sounds like the dizzy was loose and its now retarded instead of advance at 5btdc, where it should be for stock setting.

 

[shawski]

this may sound crazy, but can you rotate the distributor right now? Sure sounds like the dizzy was loose and its now retarded instead of advance at 5btdc, where it should be for stock setting.

After the rebuild, we set it to 8 degrees advanced. It ran great with that setting. I checked timing yesterday in case that was the issue, it's still set at 8.

 

[gtgt_bangbang]

FWIW bad gas is strange

If you dumped sufficient new gas in there, you might be covered, but I tried to burn up a half tank or so of two-year-old gas once.

Van ran more or less fine for first 50 miles, then sputtered & died time & again on the limp home, ran like hell until I purged it with new, then never so much as coughed again. I can't explain it but I understood it.

I don't know it's crap into the filter, always figured it was the single digit octane of old gas

 

[Ahlem]

There's a youtube video out there where a guy had the same problem on a 4 cylinder. His fix was that the coolant lines to the throttle body were clogged with silicone at the front fitting into the engine block.
I had a similar problem on a 3.0 that was cured with a TPS adjustment.

 

[shawski]

I figured it out last night and this is odd considering it's a new engine...

The constant sputter was cylinder 1 not firing. I pulled the spark plug and there was a little piece of carbon jambed in the plug gap. I cleared the carbon and re-installed, BAM, ran like a top again!

Thank you for your assistance guys! I now just have an extra fuel filter on hand.

 

[flyinhawaiian01]

Wow! I don't think anyone could've guessed that one! Good job finding it though!

One thing for sure, if your engine isn't running quite right, pulling the plugs and inspecting them will tell you a LOT about what's happening! Good job finding that one!!!