P0300 P0306 Misfire fixed - fuel injector '99 4Runner

[joeflem]

Unbelievable...

After all that it was still an injector...So I am spending about $500 for something I already did. Pretty bummed. Mechanic was really cool and troubleshooted it for free until he could not find the problem. Compression was awesome and no coolant leaks which was good news. Determined there was no fuel going to #2 cylinder. Thought it might be the wiring to the injector but only way to find out would be to pull the plenum which was $255. It was already there so I let him as I need this resolved. Checked the #2 injector and it was like 3 ohms resistance. So after all that the coiling in that injector was failing all along and I put it right back in #2.

What are the chances I put the same injector in #2??? Crazy. He's gonna put a OE injector back in and is 100% sure this was the issue. Said the truck runs and sounds great otherwise. I'm out $500 plus what I already spent but as he said at least I have taken care of a lot of the issues that might come up anyway. Think I'm gonna pull the coils and return them though and maybe try to recoup some of my money.

 

[hwyix]

It still puzzles me how the engine can report a P0306 which is ignition related,

P0306 == misfire in cylinder 6. That does not mean ignition.

That means how ever they coded there computer to find a missfire ( usually some kind crank / cam sensor rotation ) rule. Many things can cause a missfire. spark plugs/fuel injector/intake crack on single cylinder/rings/valves/etc...

 

[bpowa]

Nope I haven't done either of those and am scared now its something major. Pretty bummed. Bought this 4Runner six months ago because it ran so well and all the rave reviews about them. Losing my work car soon and needed dependable transportation. Can't afford to sink a ton into this but no real choice so I'm tapping out. You're right...all the cheap DIY stuff has been done.

Nothing but awesome reviews for this shop thats local to me called Yota Masters. Supposed to be honest trustworthy guys who know their s**t when it comes to Toyotas. I'm gonna take it to them and run down everything I've done/found and see what they find. Crossing my fingers...I will update. Thanks for all the input.

So to reiterate. You sent the injectors to witchunter and the have it a clean bill of health. Then after you reinstalled it. You took it to a mechanic and found the injector still bad? Now after replacing injectors with new oem. The problem is fixed?

 

[Leebo]

P0306 == misfire in cylinder 6. That does not mean ignition.

That means how ever they coded there computer to find a missfire ( usually some kind crank / cam sensor rotation ) rule. Many things can cause a missfire. spark plugs/fuel injector/intake crack on single cylinder/rings/valves/etc...

I get it now. I was under the false impression that a misfile was only detected by way of ignition. BTW, a year later now and it's still running fine.

 

[neckro666]

help

Im kinda having the same issue with my 95 v6. It starts up fine then ill drive five min dwn the road an it starts missfiring. Then in the blink of an eye it starts running fine again. Seems to do it when ever it wants. Start ups dont seem to be a problem. Have replaced spark leads. Coil. Dissy cap and rotor. Could it still be injecters???

 

[nicheel8]

Leebo...thank you very much for this post. My 4Runner has 196,000 miles and was thinking the worst last month.

I started off with the P0133 Error. Replaced O2 sensor, cleaned MAF, and replaced Air Filter. Good to go.

Couple days later P0306. New Coil, Spark Plugs, Wires, and Fuel Filter.
Good until engine warmed up. P0306 comes back.

After reading your post and finding some great "how to" forums I took on the challenge. After 4 hours, I took my time, mapped every nut and bolt, and had to run to Autozone for two vacuum hoses that cracked-that never happens. I love my Yotas, but that #6 injector is a pain.

It's been 2 days, over 70 miles driven and I am cautiously optimistic.

Man, I love the internet!

 

[AndreiR]

After all that it was still an injector...So I am spending about $500 for something I already did. Pretty bummed. Mechanic was really cool and troubleshooted it for free until he could not find the problem. Compression was awesome and no coolant leaks which was good news. Determined there was no fuel going to #2 cylinder. Thought it might be the wiring to the injector but only way to find out would be to pull the plenum which was $255. It was already there so I let him as I need this resolved. Checked the #2 injector and it was like 3 ohms resistance. So after all that the coiling in that injector was failing all along and I put it right back in #2.

What are the chances I put the same injector in #2??? Crazy. He's gonna put a OE injector back in and is 100% sure this was the issue. Said the truck runs and sounds great otherwise. I'm out $500 plus what I already spent but as he said at least I have taken care of a lot of the issues that might come up anyway. Think I'm gonna pull the coils and return them though and maybe try to recoup some of my money.

First of all, thank you for posting your experience!
Did a new injector fix it? I'm having exactly the same symptoms as you described. The code is P0300. Put new spark-plugs, run three gas tanks with injector cleaning fluid with no effect. Now should I go straight for injectors (why bother with other steps?) ?
There is a set of injectors on Ebay for $150 a set
My friendly mechanic will install it.
Is it a good option?
Thank you for your help!

 

[DaveInDenver]

I too had the P0300 & P0306 and stuttering with no power on acceleration or just pulling from a stop. Came on very abruptly.

Short version = (no pun intended) spark wire to #6 was bad due to accum rust/moisture spark well.

Non-short version = My mechanic found it in one hours of inspecting all the usual disconnect/damage suspects.. nothing obvious. Cleared codes, swapped #6 wire to #4, and CEL codes followed to #4 cyl with a P0304. Yea! Put in all new wires (plugs and mass-air svc too) and we're golden.

My bad. 200K on OEM spark wires.

I was way lucky compared to so many of the above ordeals.

Good site.. always find useful (sometimes scary) info.!

2002 SR5, 200K, Auto

 

[310Nesta]

Similar problem

I'm having a similar problem with a very sporadic loss of power. It happens when the engine is warm and subsequently turned off. It seems to correct itself after turning the engine off then immediately back on again.

Last night on the way back from Arizona we pulled off for 30 minutes and had In & Out burgers in Palm Springs. Upon restarting, the engine popped and sputtered with an almost complete loss of power. I pulled over to the side of the road, turned the engine off then back on and continued on our way back to Los Angeles with no problems.

When I inherited the car a couple months ago the CEL was on with errors for
P0300 Random Cylinder Misfire
P0304 #4 Misfire
O2 sensor
O2 sensor heater
Thermostat open

I replaced fuel injectors #2 and #4, O2 sensor before the cat, thermostat, plugs, plug wires and coils. I get no error codes or check engine light now but the Catalyst emissions module is in the Not Ready position even after the ~600 mile trip to AZ and back. Other than this intermittent problem the car runs fine and I was getting about 18MPG towing a 1500lb. trailer.

 

[TheDurk]

I'm having a similar problem with a very sporadic loss of power. It happens when the engine is warm and subsequently turned off. It seems to correct itself after turning the engine off then immediately back on again.

Last night on the way back from Arizona we pulled off for 30 minutes and had In & Out burgers in Palm Springs. Upon restarting, the engine popped and sputtered with an almost complete loss of power. I pulled over to the side of the road, turned the engine off then back on and continued on our way back to Los Angeles with no problems.

When I inherited the car a couple months ago the CEL was on with errors for
P0300 Random Cylinder Misfire
P0304 #4 Misfire
O2 sensor
O2 sensor heater
Thermostat open

I replaced fuel injectors #2 and #4, O2 sensor before the cat, thermostat, plugs, plug wires and coils. I get no error codes or check engine light now but the Catalyst emissions module is in the Not Ready position even after the ~600 mile trip to AZ and back. Other than this intermittent problem the car runs fine and I was getting about 18MPG towing a 1500lb. trailer.

Lemme guess--2001 or 2002 4Runner? We need to know year; it makes a huge difference.

 

[s20004runner]

going through this exact problem now.

Do I just switch out one injector on cylinder 6 or should I switch all six?

My t4r 99 limited w/ 230K miles on it.

 

[Jahmiroquai]

Sorry to resurrect an old thread.

Going thru this exact same exercise now. I had the same symptoms of having cold starts work fine, but warmed starts throwing misfire codes.

I bought injectors from Rock Auto, not reman but off-brand. Wondering if i should return and spend the $ for OEM?

Was also planning on replacing plugs, plug wires, and coils as long as i've got the everything apart.

I have the added bonus of having to remove my gen 1 S/C to get to the injectors. Definitely don't wan to have to do this twice.

 

[AZHellfish]

So....

3.4 V6 in a 1996 4Runner. Runs good with maybe just a hint of rough idle, but not always. Throws a trouble code for a misfire in the #5 cylinder. Coils are new, plugs are new, plug wires are new.

"Listening" to the fuel injectors shows 1/3/5 all sound good. 5 might be a little quieter, but that could just be because its in the back and harder to get good contact with the long screwdriver I am using to listen.


The plug that just came out of #5 looked a little redder than the others, but not bad.

Any other causes for an isolated misfire?

Compression check?

Run some kind of miracle FI cleaner and see if the #5 FI is just dirty but pumping?

 

[Jahmiroquai]

When i was going through this, the misfire was obvious, meaning it wasn't running just a little rough - it ran like crap.

So I'm unsure if this is the same issue you are experiencing, but in my case it ended up being a leaky fuel injector. Cold starts, not problem. Warm starts, some fuel had leaked past the injector and caused rough idle on startup, also gasoline smell in exhaust.

Just an idea for you to investigate. Be super careful removing a damaged injector, the tip of mine broke off and fell down, ended up having to pull the manifold. Some pics in my build thread.

 

[mjw2002]

I am having a similar issue

My 2002 with 187k miles, started the misfire game about 6 months ago. I replaced the plugs and wires which cured it for awhile. The problem resurfaced about two months ago, codes show misfire #1 and #6 and random multiple misfires. I then replaced the plugs again and all three coil packs. No help, multiple doses of seafoam and one other cleaner $$ no help.

Recently 2 additional things started. The gas gauge shows empty randomly on start up and stays buried. Secondly I noticed the temp gauge stays toward the cool side. I checked with my code reader it said the engine was running about 199F. I am not sure if these are related to the misfire or a completely different issue.

I have not checked the vacuum lines yet. Just read about that in this forum the other day.

It sounds like replacing the injectors on #1 and 6 might be in order. I have been told a bad cam position sensor could be the issue. I am approaching time for a timing belt replacement could that be the cause of the misfires?

Any suggestions

 

[Silver4Run]

Misfire Problem

Hi All,

I know this is an old thread, but it seems relevant to the question I'm having. I was having a misfire problem for about 10 seconds every time I start up, warm or cold. The codes came back the 4th cylinder, and the ignition coil was bad, so I had it replaced along with the other 5 coils that hadn't been replaced.

Two days later the light came back on with the same code for the same cylinder, so we replaced that coil again with a different brand.

Didn't solve the problem, so my mechanic thinks its a fuel injector and is looking at it now.

Any thoughts or suggestions? Know what I should expect a fuel injector to cost? I've already spent 800 or so on the other 5 ignition coils and now I'm not even convinced they needed to be replaced. I'm growing more and more frustrated.

Thanks

 

[jasonochs25]

Hi All,

I know this is an old thread, but it seems relevant to the question I'm having. I was having a misfire problem for about 10 seconds every time I start up, warm or cold. The codes came back the 4th cylinder, and the ignition coil was bad, so I had it replaced along with the other 5 coils that hadn't been replaced.

Two days later the light came back on with the same code for the same cylinder, so we replaced that coil again with a different brand.

Didn't solve the problem, so my mechanic thinks its a fuel injector and is looking at it now.

Any thoughts or suggestions? Know what I should expect a fuel injector to cost? I've already spent 800 or so on the other 5 ignition coils and now I'm not even convinced they needed to be replaced. I'm growing more and more frustrated.

Thanks

old thread i know, but im dealing with this now. I just wanted to let you know these cars only have 3 coils that run 6 cylinders and 3 wires as well. If I were the mechanic, I would switch a coil between cylinders to rule out a bad coil or bad plug wire. I hope you are just confused as to the number of coils you were told to pay for, as there should be only 3. That being said...want to sell the extra ones? LOL. I'm kidding.I'm in the process of changing my injectors because all the coils, plugs, wires are testing good.

 

[tkduke77]

Just wanted to add another datapoint here. Been getting a P0305 code for the last month on my 2000 (195k miles), but only when starting the truck warm. Cold starts in the morning and again after sitting for 3+ hours were fine. If I started the car after a break shorter than 2-3 hours, the car would immediately shake and throw the same P0305 code.

I initially took it to a shop and they recommended replacing the cylinder 5 ignition coil and spark plug. I went ahead and replaced all of the coils and plugs and it didn't help.

Thanks to threads on here, I saw others reporting a fuel injector issue because of the cold vs warm start indicator.

Pulled the fuel injectors out on Saturday (replaced the valve cover gaskets and seals while I was in there) and sure enough the lower o-ring on the cylinder 5 fuel injector was all sorts of twisted.

Put everything back together with new o-rings for injectors 5-3-1 and so far so good. :banana:

 

[NCRidgeRunner]

Not as much luck as you guys have had

Hi all... thanks for the great info here. I’m about to pull my hair out over this. I’ve been getting cylinders 1 and 5 misfires. I’ve replaced plugs, wires, all three coil packs, and 1 and 5 injectors, all with OEM Denso parts from the dealer. I’m still having the same problem...no success AT ALL in figuring it out or fixing it....Any suggestions on what to do next?

 

[Brandt]

I have another possibility to throw into the mix: the ECU. I've read that a failing ECU can cause the same CEL misfire codes as an ignition or fuel problem. Are there clear ways to clearly eliminate the ECU as the culprit, short of replacing the module or replacing the plugs, wires and coils or motor vaccing the injectors?