Engine bogging down - fuel filter ??

[Tanner]

Hey guys, my engine was running fine in the driveway and then at RPM's it started bogging down until you gave it more throttle and then it would die if you left it.

My first thought was bad gas, but I don't think so, to be safe I'm gonna drop some heat in there and some 101 octane tom to help bring the octane rating back up from over the winter.


Second thought was fuel filter. I've only changed it once, so it's got 2 years on it (boat only has 70 hours). Can the filter element that these 340 MP's from an 06' be bought at a napa or o-reilly's?


Third thought - IAC ... gonna clean it first thing in the morning.

Any other ideas guys?

[chpthril]

Instead of adding anything like "Heat" or "Octane Boost", I would top off the with fresh gas and add a bottle of Stabilize. Octane boost and other such products, are actually going to raise the flash point of the air/fuel mixture, which may not be what you want. If the the gas has spoiled, it's lost its potency. In some of these products, the main ingredient is Isopropyl Alcohol any way, nor sure what it may due to the rubber components in the fuel system.

Wont hurt to change the filter, but try to catch as much of it's contents as possible in a clean catch pan and put in a glass jar. this way you can see what came out of it, mainly the amount of water. Probably wont find this filter at an auto parts store.

IAC is no longer in the picture as soon as you start to open the throttle. I wouldn't bother with it as the problem is not an idle problem. I think the spoiled fuel route is the best to pursue first.

[lightning59]

x2, I'm with chp.

[Tanner]

Instead of adding anything like "Heat" or "Octane Boost", I would top off the with fresh gas and add a bottle of Stabilize. Octane boost and other such products, are actually going to raise the flash point of the air/fuel mixture, which may not be what you want. If the the gas has spoiled, it's lost its potency. In some of these products, the main ingredient is Isopropyl Alcohol any way, nor sure what it may due to the rubber components in the fuel system.

I wasn't gonna add an octane booster, just some fresh 101 race fuel (ok, so it's not true 110 race fuel) that I got to help boost the octane. Really just wanted to bring the octane level of the old gas back up. Wanted the two to mix

As for the filter.... do you think I can get away in a pinch w/ just cleaning out the old filter if I can't locate one? The closest tige dealer is an hour and half away.

[chpthril]

I wasn't gonna add an octane booster, just some fresh 101 race fuel (ok, so it's not true 110 race fuel) that I got to help boost the octane. Really just wanted to bring the octane level of the old gas back up. Wanted the two to mix

As for the filter.... do you think I can get away in a pinch w/ just cleaning out the old filter if I can't locate one? The closest tige dealer is an hour and half away.

Spoiled gas and octane levels are not related. Gas is a blend of Octane molecules and Heptane molecules. Going stale doesnt change the % of molecules, it changes the volatility. Spoiled gas still has the same ratio of octane to heptane as fresh gas, it just has less power.

The octane level (octane to heptane %) is an indicator of at what temperature the fuel will ignite. 87 oct (13 heptane/87 octane)has the same BTU's as 93 oct (7 heptane/93 octane), but the 87 will ignite at a lower temp then 93. This is why some vehicles, such as those with high compression engines, will spark-knock (pre-ignition) on a lower octane fuel. This is because the higher temps ignite the fuel before the ignition system does. Hi octane fuel, as stated earlier, contains NO more energy then normal octane fuel, it's use is intended to allow piston to reach DTC, in other words, the correct spot for normal ignition, without flashing off early which result in abnormal noise, loss of power, and engine damage.

If you truly have spoiled fuel, no amount of 110 oct racing fuel will fix it. It may actually compound the problem because it takes so much more heat to ignite the 110 then it does to ignite the 87 oct. One bottle of stabilize and a tank of fresh 87 oct will be the best course of action next to draining the tank and refilling.

[philwsailz]

So, Tanner, don't bother dumping any of this in...

[Tanner]

newest update. I yanked the fuel filter. No water to be found. Gas looks good.

Fuel pump maybe?

[philwsailz]

Seriously, check to make sure your tank's vent tube is not clogged. It is common to have a dirt-daubber nest clog one. The effect is the same as if you have a vented outboard tank, and forget to open the vent valve. YOu suck a vacuum on the tank and then starve the motor.

Try loosening your filler cap and see if the problem continues. If the problem goes away, look to your vent. If loosening the filler cap does not fix it, you haven't spent any money checking...

[Tanner]

Something that I forgot to mention. When I had the fuel filter off, it smelled horrible. Like something was wrotten. I'm still maybe leaning towards bad gas. Gonna try your trick in a bit Phil.

[chpthril]

If it dont smell like gas, it's spoiled, no doubt. Spoiled gas has an odd but real foul smell.

[Tanner]

I had always seen bad gas smell like varnish. But this was def. wrotten.

Final case was it was bad gas. Apparently I only had a quarter of a tank (I was having issues w/ air in my tank last year and only taking a little bit, so I would think it was full and my guage isn't working). Anyways, 3/4 of a tank of 91 octane, a bottle of stabil and we're in business. Running like a champ.

[whitlock87]

Tanner
Do you add STAB to your gas at the end of the summer?

[Tanner]

Yes