97 Ranger sputter / hesitation from stop

[rdubs]

I have a 1997 ranger 2.3 automatic transmission, 123k miles.

Since the weather started getting warmer I noticed a pre ignition sounding ping. So when I changed the oil last week, I added Lucas oil additive, cause I had a bottle lying around (never used it before, probably not related).

I also reversed the spark plugs mod where you switch some of the wires on the secondary plugs, set those back to normal. They had been like that for 4 years without any problems. Cleaned the MAF sensor, and un-hooked the battery for 10 mins to reset computer.

Plugs and wires were replaced about 15k miles ago.
Fuel pump changed 50k miles ago.

Now when I accelerate from a stop, especially when stopped on a hill the engine does this sputtering, bogging down type thing. If I let off the gas and start again it clears up.

It doesn't do it if I ease on the gas, only when I try to accelerate to fast. Also it does not do it when I am moving. If I am going like 10 mph I can punch it and it takes off fine.

I am going to clean my air filter when I get a chance tomorrow, could it be that I broke a spark plug wire? Would that cause a mis at all speeds?

I think I changed the fuel filter a few months back but can't remember usually change it every Feb.

Any thoughts appreciated, thanks.

 

[Mark_88]

If the sputtering clears up under certain conditions it is not likely a broken spark plug.

You said it started recently (since warm weather) but that could be a few months so if you could narrow that down a bit.

Do you always buy your gas at the same place or have you varied the source of the fuel?


I've seen many causes of similar symptoms ranging from a wonky sensor to fuel filters and in some cases a short that clears up for whatever reason but usually returns under specific circumstances.

But most other things like physical parts being broken or dirty would give you problems across the board and not clear up typically.

One of the first things I would recommend is to check for codes. Since you reset the computer it needs a bit of time before the codes would appear (a bit of driving to warm up the vehicle usually does it).

 

[tomw]

rdubs:"Now when I accelerate from a stop, especially when stopped on a hill the engine does this sputtering, bogging down type thing. If I let off the gas and start again it clears up."

I think you have a FPR and a fuel return line sending excess fuel back to the tank. The fuel pressure regulator reacts to manifold vacuum change, such as when you open the throttle. If the regulator is dysfunctional, the pressure won't bump, and the fuel/air mix may be too lean, causing hesitation. I'd check that the pressure regulator works, and the pressure bumps when checked with the engine running at idle. Just pull the vacuum line and watch the gauge.
In many cases, when an engine 'falls on its face' as the throttle is opened, one suspect would be the MAF, or its ribbed air tube leading to the throttle body having leaks between the ribs. Bad air flow information would mis-inform the computer that more fuel was needed, right NOW, and you'd get stumble hesitation, etc.
So, the actual delivery problem or the reported need problem are two possibilities.
tom