On/Off Misfires and CEL 1999 4runner

[hardiek]

I have a 1999 4runner sr5 4x2 having misfires and cels that keep going on and off. When the codes and cel are on the vehicle runs very rough and is barely driveable. When they are off it drives completely normal.

The misfires so far have been on 3 and 4 which are not connected to a single coil so wires and plugs and coils seem unlikely.

Any ideas? Thanks.

Kevin

 

[hardiek]

Also, I filled up with new gas so gas shouldn't be an issue either.

 

[TheDurk]

Also, I filled up with new gas so gas shouldn't be an issue either.

How old are your plugs? I won't start to troubleshoot a misfire on anything unless the plugs are new. That way you can take a careful look at the old plugs which can tell you a lot. Learned the hard way. And if wires aren't halfway recent, I'd do those, too, even if they aren't the problem.

 

[hardiek]

replacing them tonight. will report back tomorrow.

 

[TheDurk]

replacing them tonight. will report back tomorrow.

Make sure you look carefully at the three and four plugs. Pics would be ideal.

 

[hardiek]

good idea and will do.

Strange thing is the 4runner ran perfectly fine this morning so the problem is so inconsistent which makes no sense to me.

I am going to replace the plugs and clean the MAF and take pics of plugs. Anything else I should do?

 

[LittleCaesar]

Get a code scanner to take in the 4runner to be able to read them when they occur.

 

[hardiek]

P0307 on cylinder 4 and p0125. that is all.

 

[hardiek]

all plugs replaced with NGK bkr5ekb. The boots and wires looked okay so I left them. Here is a photo of the ones pulled out.

View image: IMG 20130615 125803

No CEL codes yet but still running rough. Here's the weird part. If the car is fully cooled off (has not run for awhile for example or first thing in the morning) it does not run rough at all. It runs perfectly fine for as long as I don't turn it off. When I turn it off then turn it back on 15 minutes later it runs rough until I let it cool down again. So strange.

What next? I am adding some injector cleaner into the fuel to see if that helps. Thinking of cleaning the MAF?

 

[hardiek]

just cleaned the MAF and added injector cleaner to the fuel. results will follow as soon as the MAF is dry. Also pulled the EFI for an hour to reset the computer. Hopefully good news will follow.

 

[hardiek]

no luck. cel light back on. new plugs, injector cleaner, maf cleaned, efi reset, gonna take it to autozone for a code read as soon as it cools down to drive fine again. if it is misfire on 4 again I am gonna replace the coil and plug wires next. After that I am out of ideas. Anyone else have any ideas?

 

[Jay4hand]

first i would check for a vacuum leak, if there is no leak, I would replace your MAF

 

[LittleCaesar]

Are the 02 sensors original? I'd start there.

 

[hardiek]

How can in tell if they are original u2 sensors?

 

[hardiek]

O2 sensors?

 

[TheDurk]

P0307 on cylinder 4 and p0125. that is all.

I assume you mean p0304. There is no such thing as a P0307. P0125 is suggestive of O2 sensor. I know it sounds like something else (Coolant Temp sensor) but it's usually the front O2.

 

[hardiek]

same p0304 misfire code on cylinder which is a slave boot off of coil 4. Since cylinder 1 is not misfiring i don't think its the coil. Today I am replacing all of the slave boots which I hope will fix this for good. I am also going to switch the coil with another coil just in case there is a bad connection to the slave boot. that way if it comes back it will at least move to a different cylinder. stay tuned.

 

[hardiek]

any chance that a bad coil would only affect 1 of the 2 cylinders?

 

[brian2sun]

any chance that a bad coil would only affect 1 of the 2 cylinders?

Yes that can happen^^. But since you said it acts up when it warm, after you shut it off and restart it after 15 minutes, there is a good chance it's the fuel injector. When an injector goes bad, it will often leak fuel into the cylinder after you shut it off and while the engine is warm. You come back 15 min later and that cylinder misses until that fuel burns off, then it normally runs good after that. Does this sound like your scenario? Missing from an injector can be random too.. like it'll run good for an hour, then start missing out of the blue without shutting it off.
I know all about bad injectors.

Swap the coil packs first to make sure the miss doesn't move so you can eliminate the easiest stuff first.

Also, have you ever got a code for a miss on #3.. or is it just #4? Just one hole missing would support the bad injector theory more than 2 missing holes.

 

[hardiek]

brian2sun,

Great information.

I moved the coil packs and the problem stayed on cylinder 4 so I was thinking its the fuel injector. I don't think I have ever had a miss except on cylinder 4.

Everything you noted makes sense except that it never starts running again again until the car cools all the way off once the problem arises. This normally takes a couple hours and then its fine. Maybe once it gets warm its just leaking heavily into the cylinder and it can't operate properly again until it cools all the way back down?

Thanks again.

Kevin