My 4runner has started running like absolute crap. Here's what happened:

It was running great. I stopped and got around half a tank of gas one day at the local cheap no-name gas station. Filled up, and about 3 miles down the road it started running bad. Bad performance, misfiring, and sluggish off the line. I stopped and got gas at a Citgo station and filled it up the rest of the way. It ran a whole lot better on the way home, and I didn't think anything about it. Ran that tank of gas through and it was running fine.

My dad wanted to borrow the 4runner a week or two later because it has air and his car doesn't. He stopped and got gas at a Texaco station, and said when he pulled out, it started stumbling at idle. He drove to work (about 2 miles away from the gas station) and went in. Said it was running like garbage on the way home that night. Same thing, stumble at idle, backfiring and popping in the exhaust, sluggish and no power off the line. He put a can of injector cleaner in the gas tank, to no effect.

I pulled the plugs and they were worn and had some deposits on them, so I put in 6 Denso plugs and a set of Denso plug wires. Went ahead and replaced the distributor cap and rotor button while I was at it.

Still runs like garbage. Same thing

I've disconnected the TPS, runs the same. Disconnected the vacuum lines to the EGR, and it still runs the same (and there doesn't appear to be any vacuum in the lines going to the EGR?). The ecu is not throwing any codes.

Any ideas? It's about to drive me crazy!

 

Not knowing for sure what may be going on, but considering it happened immediately after a gas stop, I'd think either water in the fuel or otherwise contaminated fuel. So first I'd do is run a tank or two of gas from a station you trust with a can of fuel system water remover or isopropyl alcohol (about 1 quart per tank), then change the fuel filter. If it doesn't clear up after that, then it's time to get into the serious troubleshooting.

 

I'm thinking fuel-related, I went and pulled the gas cap off after it had been sitting for about an hour, and it hissed loudly - loud enough for my fiancee to hear from across the driveway. It has never done that before, and none of my other 4 fuel injected vehicles do this... would that indicate a blockage at the filter, since the fuel filter is located after the pump?

It's the OEM filter, by the way, got 180,000 miles on it.

 

180K is a lot of miles so I'd say the filter does need changed. As for the pressure in the tank, my 88 does that now and then, more often when it's hot outside and when the truck does a lot of short trips. It's actually normal and is caused by pressure building in the tank due to evaporation and by the charcoal canister not getting purged.

 

Okay, so I replaced the fuel filter today. The old fuel filter had some of the nastiest stuff come out of it, and was really hard to blow through. The crap that came out was mud-brown and slimy. Didn't look to be rust, but it looked terrible, and was slimy and oily on my fingers. The truck seems to run a little better but it's still running like trash. I put a bottle of Chevron Techron fuel injection cleaner in it, and haven't added any gas yet. I'm at about 1/4 tank at the moment.

What else should I do? I'm at a loss here.

It's also idling low. Around 400rpm with the air on. Usually idled at around 500-600.

 

Possibly the pick up filter on the fuel pump. Means dropping the fuel tank....and, I'm sure you love to hear that.

 

you might also only have to wait a bit for the ecu to compensate for the better fuel flow or just unplug the battery for a minute or two.

 

Hey guys, thanks for all your help, by the way.

I'm pursuing the bad gas angle right now, is there any way to get a sample of the fuel? Like, if I unhook the inlet from the fuel filter, run a line from it into a glass jar, and then try and crank the truck, am I going to kill anything? I wouldn't hesitate to do this with a carb, but I'm not 100% on fuel injection stuff .

 

i had the same symptons a little more than a month ago. it ended up being a bad fuel injector in the #2 cylinder. (driver side, closest to radiator). i call it a stumble. whenever you press the gas, i just stumbles in all rpms.

 

That's very similar to what is happening here. It mostly stumbles at lower RPMS, and seems to clear up past around 3000rpm. Still no power, and it idles like crap. I'll look in the FSM, but how involved is it to pull the injectors? Just looking at the engine I bet it's a huge pain to pull the intake plenum

 

you are right about the plenum. vacuum lines are my weakness it seems. the injectors twist in. its not hard to get em out. personally, i had a buddy do it for me. i bought the injector from Bennett auto (florida based company) for $43 dollars. it was reman but still says denso on the side. Hence the core charge.

 

stumbles at lower rpms?, still sounds like your not geting enough fule like someone mentioned a bad pickup screen. and it is a pain to get those intakes off

 

I think I know the answer to this question after looking at the FSM, but is there any way to test the injectors aside from pulling them and manually testing?

Edit: Just for the record, no coolant is missing, coolant is still clean and green. No particulates or coolant in the oil. I'm (hopefully) ruling out the headgasket.

 

i know how to test the connections to injectors. i know autozone has a noid light kit that you attach to the connector, turn engine on, and accecelerate. the hight the rpms the brighter the light. i do recall that the lights do not say that they work for toyota injectors, but there is one that does if this makes any sense. as far as the injectors themselves, im not sure.

 

I hate to bump this, but I'm still having problems. Here is what I have done:

1) Denso plugs, Denso wires
2) 2 distributor caps and rotor buttons
3) Replaced fuel filter
4) Unplugged EGR
5) Unplugged cold start injector
6) Unplugged TPS
7) Replaced air filter (just for the fun of it)
8) Checked for vacuum leaks by spraying carb cleaner around the vacuum lines


What else? It's still running like garbage, low idle, misfiring, popping in the exhaust, no power from a stop. No signs of blown headgasket.

 

how many miles have you put on it since the problem started... enough to run a few tanks of fuel through? did you try fuel system water removal stuff or isopropyl alcohol?

 

I dont know about your area,but the ethanol in the new gas causes phase seperation.The ethanol will not mix water,and seperates the ethanol from the gas,and pushes water to another layer.So you have water,ethanol,and gas.So when pumped from the sump,it picks up unbalaced product.The other problem is when the ethanol is put into storage tanks,the ethanol acts as a cleaner.It will break down any deposits and sludge.These will pass thru the old style filters on the pumps.The pumps are now suppose to have filters that shut down when they sense water.If the station is like you mentioned a cheapo fuel stop,they more than likely not compliant with the new standards.So if you got a hevry dose of ethanol it could have cleaned your fuel tank,and pushed any moisture,and trash to the filter,and to the injectors.Also my truck acted up and it was a resticted exhaust.

 

Okay, thanks for the replies.

It had about 1/4 to 1/8th of a tank of gas in it when it started doing it, and I hadn't really driven it far since then - maybe 5-10 miles - since it was sort of dangerous to drive, it was so slow - even flooring the gas, it took it nearly 15 seconds to hit 30mph.

I went and bought two bottles of Iso-Heet water remover and dumped them in, and then braved the trip to the Chevron and put in about 10 gallons of gas, bringing it to 3/4 tank. I've driven it maybe 10 miles since then, and it' running a whole heck of a lot better. Not 100%, but maybe 75%. It's still idling rough and still a little slow accelerating from a stop, but it's actually driveable now. I'm going to drive it over the weekend to cycle some fuel off and then top it off again when it hits 1/2 tank again.

It seems like it gets a little worse when it gets warm, for whatever reason.

Also, let me get your advice on a possibly related issue: the floorboard on the driver's side gets really hot about 12 inches from the gas pedal. Like, with a bare foot it's ALMOST uncomfortable to let your foot rest there. You can feel the heat through your shoe, too. It has done this before all these problems started, and I didn't know if it was normal for these trucks?

 

things like this are sometimes nice to know before hand...

 

The exhaust thing? I never really thought anything about it, it's done it since I bought it, when it was running fine. Whoops

For what it's worth, the muffler is starting to crack where the exhaust enters the muffler. You could hear the exhaust leak a whole lot more since it started running like crap.

I just put the Iso-Heet in tonight, after you suggested it. Not sure if that's what helped it, or the new gas, but something made it start running better.