Vehicle is a 2000 Limited. Auto. 115k miles.

I bought it about a month and a half ago. In great condition. Recently had TB/WP change, as well as radiator change. Since I’ve owned it I’ve cleaned the MAF/TB, changed the fuel filter, plugs/wires, and other minor things.

About a week and a half ago I took a 300 mile round trip (mostly highway miles). On the last leg of the round trip I stopped to get gas with about a quarter tank left. I filled up, put the cap back on and went to start my car. Now usually when I start my car in the morning or after it sits for a few hours it cranks 3-4 times, lasting about 1 second, and then it fires up nice and strong. After driving for a bit and I go to start it usually fires right up, but almost sounds like it barely starts or starts week. This has happened since I’ve owned the car. This time after filling up it made a different sound. It seemed more drawn out but wasn’t a crank. Unfortunately I can’t describe it much better than that, but it was definitely different and I noticed it.

I put it in drive and started to go. When I pulled away from the pump I noticed the entire vehicle was a little shaky. I got to a stop sign and slowing down/stopping/then initially speeding up it really had a nice shake to it. Almost felt like it was all going to fall apart on me. About a quarter mile into this I got a blinking check engine light. I pulled into another gas station and popped the hood. I had a guy with me who does a lot of work on 4Runners and he didn’t have an answer off the top of his head, bad gas was thrown around, but we weren’t sure.

Finishing the drive back home (about 70 miles), once I got passed about 30mph, there didn’t seem to be any shaking. The car drove fine and I didn’t noticed any engine power loss or anything like that. When I got home the low speed/stopped rattling was no longer present. We checked for codes and nothing came up. I turned my car off for about 15 minutes. Fired it back up and the problem came back.

I had burned about a quarter tank so thinking it might be bad gas I went and got some more to finish off the tank. After filling up the problem went away again. I got some stuff to pour in the gas tank to clean things up a bit and everything was great.

When the issue happened, it seemed like my engine physically shakes a bit more. Also, the car seems to sputter a bit. I noticed the exhaust pipe turns into more of a machine-gun-like output, rather than a consisted flow. Those are the only other symptoms I noticed.

Fast forward a week, and one refueling at about a quarter tank, I took a 30 minute drive. Stopped and turned the car off for about 5 minutes, started it up and drove off. I didn’t notice the weird starting noise this time, but it did do the typical weak sounding start I mentioned happens after I’ve driven for a bit. About a quarter mile down the road I felt some shaking and my check engine light blinked once and didn’t again. Shaking went away after about another quarter mile. Stopped and started the car again and shaking came back with a check engine light that stayed. Turned it off let it set and then on, shaking went away and has been gone for 2 days.

I do believe some bad gas could still be in there, if the issue actually stems from some bad gas. Other than that I have no idea. The guy that works on 4Runners did suggest maybe a spark plug issue, which could be possible since this was my first time ever doing plus/wires on a vehicle. I’ve read elsewhere and think maybe a fuel pump could be the issue, but I wanted to check with you guys first. Hopefully you can point me in the right direction.

Thanks in advance for your help.

Since the CEL comes on, it would be best for you to invest in a code reader. I bought my 1999 4Runner a couple of months ago and it had a very similar problem. Severe front end shake when stopped. The reader said it was a Cyl 4 misfire and I ended up replacing the fuel injector to fix it.

I definitely plan on grabbing one of these soon. However, when we checked it for codes the first time it came up, nothing showed. Might have to grab one for myself so I can test it again.

How easy was replacing the fuel injector? (as my post referenced, I don't have too much experience working on cars)

Well you will want to get a mechanic's manual first. Haynes or Chilton's at minimum. It isn't difficult and it really depends on which injector you have to replace. The previous owner had the dealer replace the #3 injector and a month later the #4 was giving the error code. I chose to replace all 6, and send out the 5 'good' ones to get refurbished. The injectors for #1,3,5 are on the passenger side and are probably 'easier' than #2,4,6. The driver side injectors require you to remove the 2 piece intake manifold, so there are a few more steps. No special tools are required, but you will want to get new gaskets for the manifold and you may as well do a proper cleaning of the throttle body, AIC valve and such. As soon as I replaced the injectors the engine was smooth, but the idle was too high. So I replaced the AIC valve to fix that. I now have 5 spare injectors and a spare AIC valve for the next time. You probably won't need to do that, but at least give it a cleaning. You may want to use new gaskets for the throttle body and AIC valve as well. That said, you really need to get a code scanner to avoid just throwing parts at it. It is useful for other vehicles you may have and/ or friends to borrow. They range in price from about $20 to $150. The Actron CP9125C from Summit Racing is $66. You can find something at AutoZone for probably half as much. Don't attempt any repairs without some sort of manual. I have both the Haynes (very useful), and the Chilton (OK), as well as the Toyota Service Manual (pretty expensive). Good luck. I don't have a lot of experience either, but I have worked on simple repairs on my autos for a couple of decades. This vehicle is almost a pleasure to work on. It seems like most things were pretty well thought out (engineered) to make it easier for DIY wrench turners. At least easier than most of my other vehicles have been.

I appreciate the response. With all that in mind, I think my next step should be to get a code scanner as well as the Haynes manual. I had originally had my eye on the UltraGuage that they suggest in the Gen 3 guide. My question is: does the UltraGuage read codes the same/as well as the one you mentioned above? Are there any advantages of one over the other?

Again, I appreciate you taking the time to respond and help me out with this.

Actually, I think I'm just going to go with the scanner you suggested. It's available at my local auto store so I can grab it today and maybe get some clarification on this issue.

Although an inexpensive code reader is a good investment, you can just have the folks at AutoZone/Advance Auto, etc read the code for you. They will do it for free.

Blinking CEL is bad - that means you are potentially damaging the catalytic converter due to misfire. Not the end of the world but not good.

Lots of reasons for a misfire and you can replace a lot of good, expensive parts chasing it. Diagnose the issue before you start throwing parts at it.....folks are here to help.

Buckaroo

Following the advice from the previous poster, I ordered a code reader and have it waiting for pickup after I get off work. Unfortunately, the Advance Auto Parts in my area doesn't do code reading any more. I asked when I first got the vehicle and they said they stopped about a year ago.

The blinking CEL was only temporary, I'd say about 10-15 seconds, and then it went solid. Not sure if that makes a difference.

I'll update with more information tonight once I get my reader and pull the codes.

Thanks for your reply.

As Buckaroo stated a blinking CEL is REALLY trying to tell you to let off the throttle immediately. The engine is misfiring so much lots of unburnt fuel is making it's way back to the sensors, possible damaging them if operation with a blinking CEL continues.

Don't drive it like this, find out what is wrong. Luck.

So I got my code reader and below is what it showed:

P0306
P0306(right next to this one was what looked like a p and d but they weren’t letters, more like symbols)
Mil off
Monitrs
1 inc
Catalyst
6 ready
Misfire
Fuel
Comp
Evap
02 snsr
02 htr

I did a quick search and it’s not looking good. However, I need a little more help interpreting all this. I’m not really sure where to go from here. Any help would be greatly appreciated.

Sounds like a fuel-related issue but I wouldn't rule out ignition as the computer reacts to what it reads in the moment.

If measuring fuel pressure were easier, that would be a good place to start, but let's assume that's good because you're not getting "bank lean" codes - or any codes that stick.

Assuming you've cleaned your throttle body, checked proper operation of the TPS, cleaned IAC and MAF sensor, have you reset your EFI table yet? It probably wouldn't be a bad idea.

Before you go chasing injectors, you might want to try a fuel treatment plan over the next few tanks. I've done this to all my cars at one point or another, and it starts with buying 4 cans of Seafoam. Some people will scream bloody murder and call me a heretic, but you can drive your car clean in some cases.

Tank 1
Drive till pretty much empty
Fill Up 8 gallons of premium and add a whole a can of seafoam to tank (2 oz per gal, 16 oz can) and go home
Reset EFI.
Drive like normal till empty.
If no codes, move on.

Tank 2
Fill Up 8 gallons middle grade gas with a whole a can of seafoam added to tank
Drive like normal till empty.
Assuming no codes, move on.

Tank 3
Fill Up 8 gallons low end gas with a whole a can of seafoam added to tank
Drive it like normal till about half a tank left.
Again, assuming no codes, move on.

Drive spiritedly for about 20 minutes and pull over in an industrial or rural area and follow the seafoam instructions and get the half of the fourth can into the intake manifold using a vacuum line. A small funnel and hose made up in advance for this work well.
Shut it down and wait per seafoam instructions.
Start is up and look out for the massive cloud of white smoke.
Drive like normal till empty
Fill up your normal grade of gas.
Drive like normal after that.

This process will systematically remove deposits, varnish, etc from the intake and clean injectors along the way.

The last half of a can of seafoam will be used in your crankcase. Add to your engine oil and drive about 200 miles and change your oil. This will thin your oil some so if you have any oil leaks at all watch your oil level during this stage.

Remember, if you get any codes at any point, STOP and address those.

Good luck and report back please

Cylinder 6 misfire
Could be:

• Defective ignition coil(s)
• Bad spark plug(s), spark plug wires, or spark plug boots
• Faulty fuel injector(s)
• Malfunctioning fuel delivery system (fuel pump, fuel pump relay, fuel injectors, or fuel filter)
• Major engine vacuum leak
• EGR valve stuck in the wide open position
• Clogged EGR ports

I had a misfire code that ended up being a bad coil, but it didn't manifest like your reported experience, mine just dogged real bad under load.

Thank you for helping me out here. I’ve done the fuel filter, as well as the plugs and wires. The fuel filter I’m confident I did properly, the plugs not so much. So, I guess that would be the best place to start?

Just to update a little, when I went to work today the CEL was still on but no noticeable issues. When I left work the CEL was off and drove normal. Drove for about 10 miles, turned the car off for an hour, came back and the car shake was present followed by the CEL about .5 miles later. That’s where I picked up my code reader and it displayed the information above.

Edit: just wanted to add, when I displayed the codes the first time, a code was present that read p0306 and right next to it was what looked like a p and a d, but they weren’t letters, more like symbols. . I cleared the codes and ran it again, all the others were present but that one.

If you're gonna go back in to redo plugs (why exactly?) put a new coil in #6 - or swap another coil to #6 spot and see if the problem follows the coil.

Sent from my Nexus 5X using Tapatalk

The plugs were one of the first major thing I did on my vehicle, or any vehicle for that matter. The issue wasn’t present until after I did the plugs, although it was a week or two after that the problem began. I’m just thinking maybe I did something wrong installing them (over tightened, messed one of the plugs up).

The plugs also seem like easiest/cheapest spot to start, but I could be wrong on that.