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Discussion Starter #1
As I was leaving my apartment last night to drive up north and visit some family, my engine started misfiring. It has never done it before in the entire time I have owned the Rav4 (almost since new) and therefore it scared the crap out of me.

I started up the engine, backed out of my driveway, and pulled up to the stop sign right by my driveway. As I let in the clutch to pull away from the stop, the vehicle shuttered a bit and was barely able to start moving. I went a few hundred feet down the street to the next stop sign, and it happened again. My first thought was that my clutch was slipping, but then I realized it must be the engine. I went a little further down the street and pulled into the local gas station. I confirmed it was an engine problem, because it occured even while the Rav was in neutral and trying to idle.

The CEL didn't come on, but even if it did come on, all of the places that could have read the code were closed for the night. I figured it was either a fuel or ignition problem, although I didn't rule out a problem with vacuum lines or sensors. I replaced the spark plugs last summer, and my engine has direct ignition so there are no spark plug wires or a distributor to go bad. All this led me to the assumption that it was a fuel problem (bad gas), because if it was a bad fuel injector, plug coil, or anything else sensor-related, the CEL would have come on pretty quick.

The missing occured while idling, or under moderate to heavy acceleration. If I was light on the gas pedal, it would accelerate somewhat like normal. I decided I would go on my way, and luckily I had my tools in the back so I could fix it over the weekend at my mom's house. I would have turned around and stayed at my apartment for the night, but since the CEL was not on, I figured I could make the 1.5 hour drive up north if I took it easy. I also thought that it could just be that some water got in somewhere thanks to all the rain lately, and that if I drove it for a while that the water would dry out.

About a half hour into the drive, it started to get progressively better, and seemed to be running fine by the time I hit the interstate for the last leg of the trip. When I pulled into my destination, it seemed to be idling fine, and the CEL still had not come on yet. At that point I though whatever was the problem had gone away.

Well I started it up this morning, and eventually it started missing again. I revved the engine a few times, and finally the CEL lit up. Now that the CEL was on I decided I should take it down to the local Autozone and get the code scanned. Yes I know that there could be an error code in the ECU without the CEL coming on, but I wanted to make sure there was a code before I drove the 25+ miles to Autozone.

On my way down to Autozone I filled up the tank with premium gas and a couple bottles of drygas, in the hopes that I could just burn off the bad gas (if bad gas was the cause).

Turns out that code P301 was logged in the ECU twice, and it means there was a cylinder 1 misfire (twice). I was relieved to know the code was just a misfire, and I looked through my handy Toyota FSM to see what I could do. The FSM shows a bunch of steps to test different things, but I think I will just check the plugs and run through the tank of gas to see if in fact it was just bad gas.

I want to believe it was just bad gas, because I did fill up the other day at the shady gas station that was closed for a few months this past fall. I bet they let gas sit in the tanks before the station was reopened by new owners in December. However, I have been driving on that tank of gas all week, and the engine just started missing last night when the gas tank was about half full.

I'm going to pull the plugs this afternoon, and reset the CEL to see if it happens again. I already checked the engine oil and antifreeze to make sure I didn't blow a gasket. If it does turn out to be caused by bad gas, would it have caused any long-term damage to the engine?
 

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My father had gas stations for about 40 years. He still has rented out about three of them. Bad gas in old 10,000 Gal tanks is a common thing. I'd advice you to drain your tank and clean it out. Blow your lines and change your filters. BTW, the pump also has a filter, I guess you should check it out.

Always try to buy gas at newer stations. They have the new federal government approved plastic tanks. These tank use an inflatable insulation that must be changed every 10 years. These are the cleans gas you can buy. Of course, this is in PR.

Old, metal tank stations ALWAYS have corroded tanks, always. My father had to change ALL his tanks by federal law. He had to contract BFI to clean even the soil around the tank. At $2,000.00 a truck load of contaminated dirt. It pulled 48 trucks :x $96,000.00 of dirty dirt in just one station alone.

Also, check your electrical system. Did the check engine light went on?

BTW, if you can determine that the contaminated gas came from a specific gas station, you can sue. But you need to prove you purchase it in THAT station. If you paid with a CC, your in luck. They have to pay for all the damage to your vehicle

One important point I missed.
In these tanks, car or gas station. The dirt will alway go to the bottom. Once the station or car starts to lower the level of fuel. That is when the problem starts. :cry:
 

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Discussion Starter #3
Well I think I fixed the problem, and as far as I can tell, the gas had nothing to do with it. I pulled the coils and plugs this afternoon, and found the #1 coil and plug were wet. The other three coils and plugs were fine. It seems that some water got down in the plug recess and must have worked its way into the coil boot and shorted out the spark plug. The spark plug was toast, but the coil looked ok and needed a little cleaning.

After I discovered the plug situation, I pretty much ruled out anything else, including bad gas. After all, if it was in fact bad gas, more than one cylinder would have been messed up.

I figure that with all the rain that I've had to drive through lately, somehow water splashed up onto the valve cover and seeped down into the plug recess, where it accumulated and eventually shorted out the plug. As for why it only affected one of the four cylinders, I think that was because the other three are covered more by the air intake box, and the rubber seal on the coil pack for the #1 cylinder may not have been tight.

So I replaced all four plugs (for good measure) and cleaned out the coil pack boots with electrical contact cleaner. Put everything back together, and it seems to be running fine, so I think I fixed the problem (knock on wood). I'll go for a long drive tomorrow morning and then pull out the plugs to make sure everything is in order.
 
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