Mysterious misfire.

[cmrunner]

I know this is my first post so excuse me if i'm posting and there's already a thread about this issue, but i have read other posts and they are very similar to my problem but not quite exact. if so please redirect me.

So my 98 sr5 4runner (158k miles) was running fine until about two weeks ago when after a fill up it started bucking on the highway and spit me the engine light. Autozone read it and said it was a cylinder 3 misfire. i followed my dads advice and ran a double treatment of fuel injector cleaner through it and "blew it out". the light went out and it ran fine for about a week.

A few days ago the light reappeared along with the bucking at all speeds. I've run more cleaner through and hasn't fixed it. the light came back on but went out and stayed out after disconnecting the battery. it's still running with a misfire through.

The weird part to me is that it only misfires randomly. One start up it'll run like a champ. turn it off and start it right back up and it's misfiring and bucking. turn it off start it up it runs fine. the misfiring is almost randomly coming and going. could it be electrical like plugs or coils as apposed to an injector in cylinder 3?

Just looking to see what fellow 4runner owners and maintenance guys think it may be since everything i read seems like this problem could be just about anything. I'm looking for learning and to fix it myself before giving in to the mechanic since it seems like it might be something so simple.

 

[toyogus]

check all wires, plugs, swap out coils first, just had the same deal with mine ended up being a bad injector.

 

[bitchaaz]

change your spark plugs and get a new coil for cylinder 3. 18 bucks @ auto zone. Replace. Put back together. Thank us afterwards.

 

[kman55]

Yeah I'd check the plugs, wires and the coil packs. Could be an injector though.

 

[BrianSD_42]

change your spark plugs and get a new coil for cylinder 3. 18 bucks @ auto zone. Replace. Put back together. Thank us afterwards.

First ... do you have any smoke in the exhaust?

Pull the plug on CYL#3 ... does it look like the carbon has burned away? Is there coolant in the CYL?

I had a CYL#3 cracked head. I hope you don't.


Brian

 

[BrianSD_42]

My thread:

http://www.toyota-4runner.org/3rd-gen-t4rs/88502-head-gasket-fail-199-840-now-what.html


Others with CYL#3 failures


http://www.toyota-4runner.org/3rd-gen-t4rs/89596-cylinder-3-misfire-help.html


http://www.toyota-4runner.org/3rd-gen-t4rs/100431-so-my-head-gaskets-blown.html

:cry2:

 

[vegeetz]

I had the same problem two weeks ago...

Codes P0300, P0303

Changed spark plug, No change
Changed coils, No Change
Ran Fuel Cleaner for 2 weeks, No Change

Finally got around to doing a compression test, very low compression in Cylinder 3. Burnt valve!!! I was able to do a valve job in time before any damage was done. Now everything is working great!

So I would do a compression test and see what is happening.

 

[Diagram14]

Everything above is a possibility. Start with the simple stuff (first post guys are usually spot on) like plugs, wire, and a coil swap with one of the others you already have to see if the misfire changes to the cylinder with suspect coil(Im sure you've read similar proceedures on your searches). Even injectors are fairly simple to get to. Only THEN do you need to start to consider your worst-case scenarios, such as blown head gaskets, burnt valves, and cracked heads. If you ask me its just not worth jumping to wrist-slitting conclusions right off the bat. Good luck in the hunt.

 

[cmrunner]

well it goes in for inspection Tuesday and the lights not on now and its not really misfiring the last two days.(it did once but simply restarting it fixed it) so i cant really rip it apart quiet yet. its the fact that it randomly comes and goes without a cel is what has me. i guess next time the cel kicks on i'll try switching the coil packs and everything.

also it just had the top end ripped apart at ~120k miles when the timing belt went killed the valves ect. so all that is fairly fresh. there's no coolant missing, its not smoking, and there's no raise at all in the temp from normal.

i feel like i got a really bad tank of gas and now an injector is bad and keeps clogging and unclogging. months ago i had a misfire and just ran cleaner through and it fixed it til now. i may pull the injector in cylinder 3 and look at it.

thanks for all the advice and suggestions though and i'll keep updating. you guys are awesome.

 

[lbhsbz]

What? These are not interference engines....unless the heads have been machines way to much, the valves shouldn't be anywhere near the pistons if a t- belt breaks.

 

[cmrunner]

well my parents owned it when that all happened so i don't know for sure without pulling the papers out what was replaced. going off what my father told me. but,
pulling the service records it says the head gasket was done, new timing belt, water pump, 6 new ngk plugs, starter, valve cover gasket... so i may be wrong and nothing was done with the valves. sorry, still learning.

 

[fightman80]

easy test to see if the injector on 3 is bad...just unplug the electrical connector while the engine is running...if there is no change in the idle....chances are it's the injector.

That's how we found my bad injector on my misfire....I first changed out the plugs, wires, and a coil pack!

That easy test could save you a ton of money.....just make sure the truck is misfiring when you pull the number 3 injector plug.

 

[cmrunner]

update: so it passed inspection and was running fine until tonight. drive about 30 miles everything was fine. way back, it started missing again. this time it spit me the light. the light kept coming on and going out though. i got the codes read and it came back the same, cylinder 3 misfire (P0303) AND an o2 sensor circuit malfunction (P0130).

i'm leaning towards a bad injector since it seems to keep randomly coming and going. almost like it gets loaded up then cleared out. going to try what fightman80 suggested first. my rpm's are kinda low. ~600-700 at idle. they lights are dim and and the heat slows down. i read the rpm's should be closer to 800-1000 somewhere is that correct?

Pulling it in the garage tomorrow and going to take a look. slightly intimidated by this since it isn't a definite solution. $$$ timetimetime. trying to save as much as i can though and stay away from the garage as i'm possibly selling it. :\

 

[cmrunner]

So I went and replaced injector three after swapping the coil packs around still came.up with Misfire in three. only cost 120$ and two hours of time and It's been running better and seems to have all its power back. Only weird thing yet is sometimes at stop sign when I push the clutch to stop the rpms dip below 500 and the lights dim almost like it wants to stall.

 

[Drcoffee]

So I went and replaced injector three after swapping the coil packs around still came.up with Misfire in three. only cost 120$ and two hours of time and It's been running better and seems to have all its power back. Only weird thing yet is sometimes at stop sign when I push the clutch to stop the rpms dip below 500 and the lights dim almost like it wants to stall.

I'm glad it fixed it for you. I'm doing #2,4 & 6 injectors tomorrow. I got the P0302 last weekend and had to order the parts.

The idle issue may be due to the computer trying to correct all this time for a lean condition. It'll have to relearn the proper fuel table, but a faster way to solve this is to disconnect the battery for an hour and start the ECM out on a fresh foot.