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Hey guys, my 4Runner is barely running and I'm out of ideas, hoping some of the knowledgeable guys here could chime in. It's running extremely rough and consistently missing on cylinders 1 and 2. The exhaust smells super rich. It seems to run reasonably well after start up, I can get in it and drive and it will run fine until I come to a complete stop and/ or let the RPMs come down to idle. Once this happens it will continue to run rough and miss until it's been parked for the night.
The plugs, wires, and coils have been replaced and switched around to see if the miss moved. It did not, so ignition system is out, or at least the easy parts of it. I fiddled around a bit doing some easy things like cleaning the MAF, testing the PCV, and running sea foam through the tank and intake. I also tried listening to the injector on CYL 1, I heard ticking but honestly I couldn't really make out individual noises very well. I blame the harbor freight stethoscope.
After getting frustrated with it I took it to the only shop around that I've heard decent things about. He said compression and spark were good so he thought it *might* be fuel related. So $90 and a pressurized fuel rail cleaning later and nothing changed. I threw a new fuel filter in too because why not, no change of course. With it running so rich I can't see it being a lack of fuel.
I can't really afford to keep throwing parts at it. If I knew a good mechanic who I was confident could take care of it I'd take it to him and be done with it but no such luck. I'm really hoping you guys will have some relevant knowledge or ideas.
Just a heads up the runner has 129K on her and is still on the original timing belt. I thought this was suspect but everyone I've talked to assured me that if the timing was off it'd be way worse. Feel free to correct them if need be.
Also I've searched for this issue in this forum and other places... a lot. The threads aren't terribly relevant or helpful which is why I've started a new one. Thanks in advance guys!
Off the top, has the pre-cat sensor been changed yet? With the mileage, its a good time for it to start failing before it sets a code. That thing could be related to why your engine is running rich. Could be other things though.
However, I'd really confirm that it is running rich by hooking up a scan tool and reading the fuel trims and oxygen sensor outputs. Good info online.
Any codes?
Timing can affect misfiring cylinders. If the last one's been on there beyond 60-80k miles, I wouldn't wait, especially if there's a bad look to the belt.
Plugs, wires, fuel filter...that's not necessarily throwing parts at it...it's part of routine maintenance, so more like catching up, unless they were replaced too soon or with cheap quality.
Last edited by 75w90mantraN; 09-01-2017 at 05:56 PM.
I'm sure your timing belt is fine and not related to the issues you're having. I replaced my original timing belt at 171,000 miles and it was in good shape. Then I did another timing belt job 185,000 miles later. That belt looked fine as well.
The truck now has close to 389,000 miles and is still on the original coil packs.
To each his own. Those are just the recommended intervals. Likely not relevant, yes, and he prob would be ok extending the TB change. But if there's a coolant leak, I bet the water pump seal is done. So it's good to replace the water pump along with the timing belt. It's a tendency I've encountered on 2 models with the same engine. But first the misfire.
Misfires also tend to occur due to vacuum leaks or failing injectors, so there's another plausible avenue to look at, though those tend to make an engine run lean. If your runner really is running rich, then I'd definitely consider looking at the pre-cat sensor. More reason to get your hands on a scan tool.
Alright, took her for a test drive today after a little fiddling and noticed that she was running great for several miles and minutes (well past engine warm up) and then it randomly started missing again and continued to do so until it was parked again. I think anything mechanical like timing belt would be consistent, so we can rule that out. And yes it's overdue, I'll get that done soon but first things first.
It throws codes P0300, 301, and 302. That's miss on one, miss on two, and random/ multiple miss.
I have one of those little amazon OBDII adapters, just downloaded Torque Pro to look at fuel trims and O2 readings. I won't lie, trying to make sense of the data hurt my brain. I'll keep reading on what these numbers mean but in the mean time I'll post them here. Note that I have two sets of sensor data, one is at idle, one is held steady at 3000rpm.
The pre-cat sensor is original. Doing some research on it I see testing it isn't as simple as reading voltages. The procedures to test are over my head, any caveman friendly methods you guys know of?
The exhaust smells very strongly. My nose isn't great so I can't really tell the difference between coolant smell and rich smell. But I'm not loosing any coolant and this has been going on for quite a while now. Also I'm getting awful mileage, haven't done the math on it but it's VERY low. Maybe fuel trim data can confirm but I don't believe this is a lean miss, so faulty injectors would be out... Unless they're sticking open. But it seems unlikely that two injectors would go at the exact same time.
Last edited by thewintergentry; 09-02-2017 at 02:43 PM.
Thanks for the link, that helped. The P0300 reads random/ multiple miss fire. I figure this comes on anytime you have more than one cylinder missing, which I do, or if you've got multiple cylinders misfiring inconsistently. I don't think the random applies in my case. I've pulled these codes several times over the last couple of months and they've always been for CYL 1+2.
It looks like my short term fuel trims are within reason but my long term indicated I'm running lean. I feel like two injectors malfunctioning would be more than enough to pop it's %25 threshold and pull a code. Maybe they're partially clogged and not delivering quite enough fuel to detonate. Which leads me to my next question, obviously Desno injectors would be the preference if I end up needing to replace them. But funds are limited and the reman units off Rockauto are looking pretty good.
-Does anyone have any experience with the cheap reman units?
-Has anyone sent their injectors off for cleaning? If so to who, how much $$$, and did they come back working %100.
-I've seen some redneck solutions to injector bench cleaning... bad idea?? Never mind this part, a little reading shows that's it's a good way make things worse in a hurry.
Testing 1,3,5 by pulling them is easy enough. Will I have to pull the plenum and reassemble every time I want to remove and test 2,4,6? That sounds like a major PITA.
Sorry for just the one word reply earlier, the app doesn't like my phone and crashes pretty quickly into replies.
I had 2 injectors fail last summer, with a 3rd failing about a week or so later, and I wasn't alone. Around the same time I noticed a lot of P0300 and P030X code threads popping up on YT and connected the dots that the injectors were taking a dive. Many people, myself included, replaced plugs, wires, MAFs, etc. with no fix until the injectors were swapped out.
I bought a set off eBay for I think about $60 for all six. I had one that was DOA and the seller gladly replaced it. I thought about sending them to WItchHunter or similar (I had a good experience when I sent my 22RE injectors there) but the turn around time and down time of the truck made replacements more appealing.
The problem I ran into diagnosing the issue is that it is intermittent. I think the coil inside the injector shorts when hot or vibrated too much. So unless you ride around with a real-time scanner running all the time, it is hard to see the event occurring. Once I was confident it was an injector issue, I moved the suspected ones to see if the miss moved too. It did, problem located. The plenum is easy enough to take apart, I think I had it down to about 15 minutes start to finish for swapping injectors. I didn't separate the fuel line to the rail, just lifted the whole rail enough to get the injectors out.
Can't say about reman injectors myself, but other folks here have used them with some success (might risk of course DOA parts, but if return policy is solid, save some dough).
I once had P0300 and P303, but ended up finding out coil pack for cyl 1 and 4 were bad, along with a failing coil boot on cyl 3, and all wires and plugs in need of replacement, especially 2,4, and 6 severely worn. So its worth checking them all, IF fixing cyl 1 and 2 dont work out for you.
Still running on supposedly original injectors. I am picky about where I get my gas.
Another maintenance item to consider down the road is that pre-cat sensor. Often, when that starts to fail, gas mileage suffers, and so does the catalytic converter, which, if you live in a place that requires emissions testing, can be another expensive repair. This from personal experience.
From my understanding, a good sensor is able to consistently read the air/fuel mixture quickly and send adjustments to the ecu. As it wears down, its ability is slower. So I'd keep an eye on the fuel trims, especially if those numbers grow higher (pos or neg). Failing sensors wont necessarily register a code, but one of the first things you'll realize is how often you have to gas up.
Haaaaaa. Swapped injectors on 1 and 3, cleared codes, test drove. Nothing, miss stays on cylinder 1. Took it all apart and redid it to confirm. So the injector is fine. I inspected the connector while I was in there, looked clean and in good shape.
Also the 4Runner just sucked down a quarter of a tank in under 40 miles. That's roughly 8MPG...
Just something to consider, as I wouldn't quite rule out injectors, especially with the multiple misfire code. Solution for the OP ended up being a new injector, vs a cleaned one, to answer one of your previous questions.
I decide to give it another go with the stethoscope this morning. I can definitely hear the injectors pulsing now that I know what I'm looking for. I could listen to 1, 2, and 3. All of them were "ticking" quick and steadily at idle and load. Some things I noticed were that #2 *MAY* have been ticking a little slower than the others, it's hard to tell for sure. I also noticed that when I'd rev it up to 5000 or so then drop the throttle the injectors would pulse for a second as the revs came down, then shut off for a second, then come back on as it approached idle. It wouldn't do this when I dropped the throttle at lower RPMs. I have no clue if this is normal behavior?
After swapping the injectors she's been a little hesitant to start, nothing major but it definitely takes bit longer than before. Also the engine stumble feels a little different from before, like one of the misses is in a different spot. It seems like the miss moved with the injector but it's still throwing codes for 1 and 2.
I guess my next move is ordering a reman injector and swapping it in. Bleh.
I read something in another thread about misfires. They had two cylinders missing, 3 and 2 or something like that. The took it to the dealership and they said the injector on 2 was bad. They went on to say that 2 misfiring was causing 3 to miss because they shared a path in the intake. Or something like that, I may have the cylinder numbers mixed.
I'm toying with the idea that #2 is bad on mine and it's causing #1 to miss. The 4runner always pulls a pending code for #2 first then after some time #1 and the Random/ multiple come up. This would explain why only swapping 1 and 3 didn't change anything. But as far as I can tell the intake paths are all separate from the start of the plenum all the way to the valves. I can't figure out how this would make sense but the OP did say that all was fixed when they replaced the one injector.
Go reman on both 1 and 2. Since you swapped out with #3 and no change, that could mean #3 is also suspected, especially since p0300 keeps returning. Keep the receipt if what you get initially are duds. But consider the possibility of having to check or replace other suspected injectors. Others just replace them all. Makes the whole experience less frustrating.
The way I understand it, misfiring cylinder means there is no proper combustion going on in a particular cylinder. I would think that interferes with the whole compression/exhaust strokes, messing up the delicate balance that the engine requires, so the ecu tries to compensate.
Maybe other members can suggest or re-educate.
But keep it up. You learn more about your runner and that can be very rewarding. I'm learning just by visiting this post and a lot of other threads both on and outside YT.
Last edited by 75w90mantraN; 09-04-2017 at 10:26 AM.
One reman injector on the way. The 4runner isn't my daily right now so I can afford to play it safe a bit. I'll try replacing #2 and seeing where things stand. The pcv was a why not kind of purchase, I've heard they can cause misses too when they go bad and it's original. I'll update this thread in a few days when I get the injector in. I appreciate the help so far.
09-01-2017, 04:53 PM
