Troubleshooting Misfire

mattman

mattman

New member
I am getting a P0302 code with the following symptoms:

Engine (3.4 with 178k miles) runs fine until shut off and restarted 5-10 minutes later (like stopping for gas/break on a trip). Upon restart, the engine runs rough, misfiring and CEL will flash if I push it too hard. After gentle driving 3-5 minutes, the engine smooths out and is completely back to normal.

If I shut it off and immediately restart it, it runs fine. Cold starts always run fine.

The plugs and wires are both OEM and fairly recent (within the year). I have pulled the plugs and inspected visually, and they all look consistent. I also changed the fuel filter w/ OEM, cleaned the TB, MAF, and IAC.

Except for when the misfire is occurring, it runs perfectly, so I don't think there is a vacuum leak. I swapped coil packs just to be sure, and it's still coming up on #2.

I am considering buying a new fuel injector for #2 ... is there any additional check I should do before investing time/money into that route?

I'm thinking that the #2 injector may be leaking into the chamber when I shut it off, and messing up the fuel map when I restart it warm.

Thanks for any help/ideas -
 
Last edited:
Register to hide this ad
I think you've got the right idea.
I recall there being two or three checks you can try before you actually replace the injector.
while the engine is running; use a stethoscope or long screwdriver etc and listen to you injectors, they will be clicking. if it isn't working properly you may not hear a click on the faulty one.
You can also take a resistance measurement across the two posts on the injector plug. refer to the manual for the ohm range.
I'm pretty sure the book states another measurement that can be taken but it's slipping my mind..
try this as well: get a nice flashlight, and next time it is running rough; shut it off right away and pull the plug. use the flashlight to look into the combustion chamber and look for coolant. if the head gasket is leaking or there's a crack in the head etc you might see some green in there. check your coolant to see if it's low. (this is not common, but not unheard of either)

replacing an injector isn't too difficult. so if it comes to that, don't stress. just make sure you bleed the pressure from the system before beginning or you'll get gas on everything(ie; in your eyes) when you pop the fuel rails off.
good luck!
 
You're problem sounds like a textbook injector issue. Especially since it runs fine at cold start and then misses after you shut it off for a few minutes. It's possible that it's a head or hg issue, but unlikely. I would go ahead and just swap the injector out, especially since if it is a head issue, it's so expensive to pull the head and check, you may as well rule out the (most likely) injector first.

If you can do with out your truck for a couple weeks, sending the injectors to witchhunter like FdcCal said is not a bad idea. If you need the truck running asap, I'd just replace the #2 inj and be done with it (since you don't seem to have any issues with the other cylinders).

This is all assuming you aren't missing any coolant, don't have white smoke out the exhaust, smell sweet exhaust, etc.. (which are all signs of a hg/cracked head).
 
Last edited:
hey guys - thanks for all the helpful information. It's encouraging to see some light at the end of this tunnel. My coolant level has been normal (i should've mentioned that in the post).

I would really like to do the whole set, but our other car is a stick, and my wife can't drive that, so it would be a tough 2 weeks trying to work around it.
 
I have been able to use a short length of garden hose as a stethoscope rather than buy an expensive one. Use a bib like what is used to fill up small water balloons if you need to listen in on a tight space.
 
The good thing is cylinder 2 is on the front on the driver's side ... I was able to compare that and and the front pass. side using a long screwdriver (during the misfire at idle). They both sounded the same ... I probably should've revved it a little to accentuate the misfire, but ....

I was reading on WitchHunter's site and I really want to send them all in - i just need to work out the rides. My valve covers need new gaskets and I definitely want to do that at the same time.
 
It's also possible (and more likely) that the injector is firing fine but maybe has a bad seal causing it to leak fuel into the cylinder when you shut it off. Let it sit long enough, the fuel will evaporate and you'll be problem free. Shut it off, let it leak and accumulate, fire it back up and misfire occurs.

Teach your wife how to drive a stick (really isn't hard) and send the injectors to WitchHunter, it's money well spent. DON'T use non-oem injectors, you'll be replacing them often.

Also, while it's apart, do a compression test. That should help rule out head/head gasket issues and it's good to know the overall health of your engine anyway.

I did my valve cover gaskets while my injectors went to WitchHunter too. One of those things you might as well do while it's apart.
 
well guys ... i'm sorry to report that after replacing (all oem) the fuel injectors, spark plugs, and some very leaky valve cover gaskets this weekend, the problem is the same ... i will say the idle is super smooth now, but if i leave it shut off for 10 minutes and go restart, the engine starts hard, and runs rough for a few minutes and throws a misfire CEL.

reading the troubleshooting for P0301 - P0306, i'm thinking maybe the ECT sensor now ... my new theory (only a few hours old) is that maybe the engine temp is held fairly constant while running, and when it's shut off, the engine temp rises into a dead band on the ECT. So, say I shut it off at 190, and it rises to 200 over ten minutes, but the sensor is bad around 200, so it reports 15 or something cold, asking for more fuel.

I paid for diagnostics at the dealership, but they were unable to duplicate the problem (this was back when it started, and it seemed a lot more rare or intermittent at that time) but now that it can be readily duplicated, i'm planning to bring it in tomorrow (under the original diagnostic fee). i can tell them how to reproduce the problem, and let them tell me what it is - hopefully ...
 
Matt,

The CEL is still PO302 then? How is the wiring to the injector itself?

Have the dealership perform a fuel pressure test after its warmed up and see what the pressure is reading.

Keep us informed.
 
LittleCaesar said:
Matt,

The CEL is still PO302 then? How is the wiring to the injector itself?
Click to expand...

Caesar, Actually, I didn't check the code last night - but for the last couple months it's been repeatable P0302, and I've moved the coil packs around. I didn't notice anything with the fuel injector wiring to #2, and I took a good look at the plug wires (they're fairly new) and didn't notice anything with them either.

I think when the issue first started I had a P0303, but just once, and I've not gotten a P0300 with this issue at all that I know of.

I'll definitely ask about the fuel pressure tomorrow.

Singtoe said:
I am going to throw this out there. May be a bad igniter.
Click to expand...

Singtoe - is the igniter the ignition control module?
 
mattman said:
Caesar, Actually, I didn't check the code last night - but for the last couple months it's been repeatable P0302, and I've moved the coil packs around. I didn't notice anything with the fuel injector wiring to #2, and I took a good look at the plug wires (they're fairly new) and didn't notice anything with them either.

I think when the issue first started I had a P0303, but just once, and I've not gotten a P0300 with this issue at all that I know of.

I'll definitely ask about the fuel pressure tomorrow.



Singtoe - is the igniter the ignition control module?
Click to expand...


Have you try a spark test to see if you are getting enough spark.
The coil pack and the spark wire may look new but you can't see the issue with the eye try to isolate little thing first.
I have the same issue as you multiple misfire P0300, P0301, P0302, P0303

I did a spark test on cylinder#1, 2, 3 and 2 failed right away one misfire will cause multiple code.
I've replace coilpack and coil rubber on cylinder #2 and that seem to be my problem.
I also use die-electic grease to help grease the rubber and the spark to make good contact.
Try that first to see it is the issue if not move to something else you are getting close.
 
do a compression test before you spend more money. try doing one after it's been sitting, then do one when you think it should (ab)normally misfire.
 
If the plug was not wet at cylinder 2 when you pulled it out, then likely it was not the injector or wire harness.

Singtoe may be onto something there with the igniter. I know that there are at least two 4runners at LKQ on Rivers Ave. so you may want to pick up an igniter there for maybe around $20 (guessing) if the dealer says that is the problem.

If your compression was off, for the most part you would feel it at all times in driving the 4runner.
 
Well guys, you're not going to believe this ... I still have trouble believing it myself, but ....

The dealer called me and said #3 fuel injector was bad. I thought no way - that's what I just replaced. These were all OEM refurbs (GB) that I bought through Auto Parts Warehouse (I would've done witch hunter, i just didn't want to have downtime). So prior to the replacement, I had what I thought was a bad fuel injector on #2 that was leaking after shutoff. After the big replacement job, I had the same exact symptom. I did not check codes to confirm P0302, I just assumed that whatever I just did had no effect on the original problem.

So, apparently - one of the "new" injectors was bad in the same way (leak) and it got installed in #3, thus exhibiting the same exact overall symptom, reproduced in the exact same way.

I was doubtful that a coincidence like this could be possible, but ....

I had been able to easily reproduce the problem on demand with the faulty injector, and last night after getting the vehicle back, I have not been able to reproduce it at all - and I tried a lot. The dealer agreed to credit me back the $300 for #3 injector replacement if this didn't solve the problem.

Crazy, huh?
 
I was really surprised when you said is wasn't the injector, but they are some sneaky little bast*rds those injectors! Glad it seems to be all fixed.
 
Good to hear Matt. Unlike Brian, I am not too surprised to hear this. On YT, there have been a couple of folks who have used GB remans, replacing all six, and getting one or more that have been bad out of the box.

Me, I pulled some out of a junked 4runner the other week. When I get an extra $120, to Witchhunter they will go.
 
You must log in or register to reply here.

Members online

Total: 395 (members: 4, guests: 391)

Forum statistics

Threads
278,308
Messages
3,554,057
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top