1997 Mercury Mountaineer - Popular situation - When you run out of gas

Maintenance/Repairs
1

I was running low on gas but made it home, classic story. My vehicle sat for three days in the driveway, then I headed out towards the nearest gas station after three days had passed. When I started my Mountaineer up after three days of inactivity it was shaky going down the road, where the last time I drove, it was not. I noticed, the gas was still low, and the shaking seemed to come from the engine, the idling, at some point around 10 minutes after running, was really rough and vibrating. As you know or might have guessed, I ran out of gas on this after three days of forgetting how low I was on fuel! I biked back 5 miles, retrieved 2 gallons of gas, packed the two containers in a back pack, and brought the gas back, put it in the vehicle, and headed off immediately, (immediately this time) to a closer gas station. The whole way there the truck shook and vibrated, and it has never done this before. I have not filled the tank all the way up all day, hoping some watery fuel or bad fuel would make itself out of the engine.

I am back at the house, with hardly any gas again wondering, what can I do or what DID I to that made the idle so rough. Did running out of gas do this? Would water or bad fuel, or old fuel make the engine run so rough? I am wondering if I need to buy some octane boost and add that or fuel injection cleaner to gas I put in next time, to help even out the idle, not sure what else this could be (this being the shaking and unsteady idles all of a sudden). When I reach 45 miles an hour, HOLY Shake EM Up, the car shakes every which way and then at 50 relaxes and lesses down, but that reaction at 45 miles per hour, not good! It has never done this before, and it seems too coincidental to have happened now, after just running out of gas. I can hear the choppy sound of the exhaust and feel the vibrating idle when at a stop light, and it does hesitate when gas is applied at the green light, I am just not sure where to turn from here. Thank you so much!

Harry

2

There is not nearly enough info known to make much of a guess as to what’s going on with this vehicle. CEL, fuel pressure, any codes present, etc, etc are some of those unknowns.

Theoretically speaking, this could be caused by a failing fuel pump and especially so if it’s the original and the vehicle has not had regular fuel filter replacements.
Running low on gas will not hurt a pump. Running low enough on gas to cause noticeable running problems can damage a pump as the pump relies on the gasoline to keep it cool and to lubricate it.

First steps should be to check for codes and to check the fuel pressure.

3

Running out of gas is very bad in a modern, fuel-injected vehicle. Driving around with very little gas in the tank is also not a good idea, as it stresses the fuel pump.

I suggest you ad a bottle of Techron, FILL the tank, and drive. The FILL part is more important than the Techron. Get some gas in that thing.

4

Thanks! It does have 143000 miles and original fuel pump, so I am sure the stress of little fuel did not do it any favors…thank you so much…:slight_smile: Dumb dumb mistakes on my part…:slight_smile:

Harry

5

At that age and mileage I would sure consider changing the pump even if a fuel pressure test shows good. Pumps can fail in different ways. Some flat quit working never to run again and others may work fine for days, weeks, or months before acting up, followed by straightening up again until the next episode. Others may “semi work” so to speak and just cause general performance problems all of the time.

I would advise changing the fuel filter every 15k miles and even more often if any fuel contamination is suspected.
An engine may run fine with a partially clogged filter but it’s really making the pump work harder and this will translate to a shorter pump life.