Help me save my 4Runner | Poor performance and engine rumble

Hello all!

I am a serious DIY and repair noob with a 3rd gen...which I adore...but I need some help diagnosing...

Vehicle: 4Runner, 3rd Gen, 1997

SKU: 3.4L V6 4AT 4WD

Milage: ~79K

ISSUE:

The issues all started with a simple misfire on cylinder 4 (confirmed by a DTC check) which caused a CEL to come on. My buddy (a certified auto mechanic) and I replaced the fuel injector for cylinder 4 using a remanufactured injector from RockAuto. We also replaced the fuel filter (also RockAuto and required some plumbers tape to not leak), filled with brand new coolant, and changed out all spark plugs. Finally...not sure if important...but I replaced the engine air filter with a RockAuto ordered filter as well.

Our efforts solved the misfire for a few days, but then the CEL returned...this time with 8 codes and a litany of new issues! I, however, was NOT experiencing engine rumbles or poor driving experience. So, in true idiot fashion, I simply cleared the codes thinking that it was a fluke from all of the time that we had the manifold apart and the fuel pressure drained.

Well, I drove around a bit more and noticed the following symptoms:

- A new CEL (third in total so far in my story) appeared.

- Moderate and unpredictable rumble coming up through transfer-case shifter (4WD shifter) and engine bay at idle and low speeds.

I scanned the DTCs again and found:

1. CAT and EVAP tests NEVER COMPLETE. They sit and flash on my Innova 3011s forever until the reader throws "ERROR."
   
   
2. I have a "Pending" P0171 and a "Stored" P0171. I am not sure how the exact same code for the MAF detecting a lean run can be both pending AND stored (maybe somebody can help me understand)?
   

BOTTOM LINE:

I am very new at this and am at critical risk of wearing out my welcome with my very kind friend that has helped me thus far with this vehicle. I really care about this car since it was my grandparents', and is also just a wonderful and useful vehicle...a real classic. If possible, I need some help figuring out what the heck is going on. For what it is worth...the misfire code HAS NOT COME BACK...so I think THAT was at least solved?

Thank you!

 

Welcome

 

Resetting codes is actually a smart thing to do. Sometimes they just need clearing to see what is really the issue.

When was the last time the hoses on the engine were changed? Mine were rock hard after 250k miles. They crack and let in air which causes a lean condition.

I would try the brake cleaner trick. Start the car, let it idle w/o AC. Spray brake cleaner around the engine bay and see if the idle notches up. If it does then you've found a vacuum leak.

Clean your MAF. Make sure you do it correctly and THOROUGHLY. If you replace it, ONLY use a TOYOTA OEM MAF. No other will work for long if at all.

Clean your Throttle Body.

Check the PCV for grime\dirt. Clean it.

Those are the common issues and cheapest to try.

If it is an O2\AF sensor, you can replace those but make sure you use OEM TOYOTA sensors and make sure you are getting the correct ones. I think you have O2 as they switched in 2001 to A/F sensors.

 

welcome

 

Thank you for the suggestions! Again, I am no expert...but I think that I do hear a hissing noise coming from under the hood towards the back behind the manifold when the car is running. A buddy of mine also claims to have seen a coolant leak as well out of one of the hoses. I suppose it is possible that we damaged or placed one of the hoses incorrectly while changing the injector out. I don't even know how to safely check all needed hoses (since there are some nozzles that intentionally have NO hoses).

 

Make sure you don't get the hoses to the throttle body reversed. Bad things happen when you feed coolant into the vacuum. I only buy TOYOTA molded hoses. They make it really hard to mess up connections. A few people have replaced hoses with generic ones and messed up connections.

 

Is there a good reference for what hoses are which for a total newb like me? I know that that is the most beat-to-death request in the world...but anything with like "labeled hoses" in a picture would do me wonders. I had trouble finding exactly what I was looking for on Google.

 

Also, here is the sound I am hearing...

https://youtube.com/shorts/jZemMPzSYlg?feature=share

 

Welcome.
I would second the suggestions by negusm to try to locate vacuum leaks as those hoses may be nearing 30-ish years old. Also, you had the intake off so pay attention to those mating surfaces as well. Did you use new gaskets when reassembling? A word of caution on cleaning the MAF - your version has been discontinued by Toyota so there is no replacing with OEM at this point, so if you clean it, be careful. Also, it is a low likelihood to be the culprit. You weren't having a problem with it before the repair so... You can cobble in the new version if need be, but better to avoid the problem altogether.

I replaced all injectors a few years back and got a lean condition as well afterward. I would swear I heard a leak under the hood but could never locate it. It ran well so I drove it while trying intermittently to find it and then it eventually went away. So, I don't know if a gasket just needed some time to seat in or swell up or what but that was my experience. I also cleaned the throttle body and MAF (but not the PVC) to no avail. Good luck. It can be frustrating.

This was a decent thread about converting to the newer MAF just in case it ever comes to that either now or later.
And congrats on having a nice low mileage 3rd gen.

 

Thank you for the kind reply! I will hold off on the MAF for now then...leave it as a last resort. In the video that I linked above, do you hear what I hear? I swear there is a hissing noise as the camera pans into the back near the firewall. I did NOT change the manifold gasket after putting things back together...and I did not replace ANY O-Rings on any injectors. I simply replaced the failing injector with a Re-Man from RockAuto and smooshed everything back together. The car still starts instantly, gets into gear, and runs decently well. Low speeds or idle do NOT run well (ie: a rumble and shake that FEELS like a misfire). I do not own a smoke machine...so I am trying to figure out the best and safest way to find the leak.

 

Mine was a lot more of a hiss than that but generally, yeah.
Also, I see I forgot to attach the MAF conversion thread I noted above, so here you go.

 

One more thing, friend!

Say that I wanted to swap the OEM hoses (30-ish years old like you said) out for silicone vacuum lines like the ones shown here:

$17 Ucreative Silicone Vacuum Hose Kit 6PCS 5FT Tubing (1/8" to 3/8") High Performance Automotive Replacement (Red)

https://www.amazon.com/gp/product/B0BKKNXTNY?smid=A3FOJD52ZN34SI
Say that I ALSO wanted to swap out the old upper and lower plenum gaskets on the manifold with parts from RockAuto....like those shown here: https://www.rockauto.com/en/catalog...+v6,1272596,engine,intake+plenum+gasket,10394

How can I tell which parts are worth it? You seemed to have a good idea for the MAF...so I figure you may know better than me here too !

Hard to keep fighting a vacuum leak if I change all of the vacuum hoses and gaskets HA!

 

I've never used silicone tubing so I have no experience with. I think it's one of those things where you ask 100 people and get 47 different answers... I'll defer to someone else on that. You can also wrap the hoses tightly in electrical tape as a diagnostic to seal up any leaks. Just go through them methodically to see if you resolve your CEL. I would not leave them like that though.
I replaced my plenum gaskets with OEM - twice. I have it my head that they crush a little bit when compressed so it's best not to re-use, BUT I've been digging around and can't find a solid verification of that. I've used a Victor Reinz gasket of some flavor in the past and recall it was of nice quality. If you go that route I would get the better ones they show on that link. Not the paper one. FYI, OEM are about $15-17 each.

 

Given that I am BRAND NEW to anything car-repair...can you tell me how you would find the part number for good gaskets / hoses and where to purchase? When I go RockAuto they always give 4-5 parts options and I have no way of knowing intuitively which ones are good or not. Is there a source of truth on that? For hoses especially...they don't really have NAMES...I have seen Toyota name them "Air Hose 3" and stuff like that...very hard to look for lol.

 

Good morning. I misspoke on the gaskets. The Victor Reinz are still fine but the paper vs rubber coated embossed products were from Mahle/Clevite. I would get the embossed ones if you go that route. On part numbers, if you click on the info tab for a part on RockAuto and scroll down they usually have an OEM interchange part # that you can copy and paste into any Toyota parts site to see what they have. Sometimes there is little price difference between OEM and aftermarket. Sometimes a big difference. Do you have a convenient dealership near you? And do they have an online presence (not all do).

 

Following up. Are you getting anywhere with this?

 

Hey! I ended up taking it to a different acquaintance of mine that does auto-tech (I am blessed with connections since I work at a Trade School) and he thinks that it is leaking air "pretty badly." He fears that my other friend and I may have damaged the fuel rail / lower plenum when putting it all back together after the injector swap. I am awaiting his final word on what he thinks needs to be done to it...it will LIKELY end up being a new upper and lower gasket (hopefully no new rail or manifold or anything like that).

I think it does speak to the immortality of the car that I drove it all the way to his shop with virtually no issues other than the hissing of the leaky air. The thing is very resistant to issues lol.

I can't wait to have it back working! I will post the conclusive diagnosis and fix after this.

 

Hello, all. I have some real rough news. Here is the latest:

1. It would seem that during the injector replacement, my other friend cracked my lower manifold. I don't entirely blame him -- it is an old car, and that part is aluminum...so...soft. We are struggling to source a known good one.
2. My shop that I took it to also believes that the fuel filter replacement we did resulted in an overtightening of the filter and that this has broken / damaged / over-flared the fuel line. I am not entirely sure how this could have been done as we tightened carefully, until any leak had gone away.
3. On top of the above, they want to replace all injectors again (don't trust RockAuto ReMan.), timing belt (never done before), and all gaskets.

Is this the worst it COULD be? No. Is it a blow to pride and ego, and a quite confusing place to end up after thinking we had saved some money on DIYing the repairs? Yes. Yes it is.

Not sure if I will have the money or confidence to go through with fixing it now. I don't even KNOW where to get lower intake / fuel lines since they are not made anymore, and junkyard parts are dodgy. I may have killed it boys . Feels pretty bad man.

I would take any suggestions at this point. Other than these issues it is in such gorgeous shape. Such a shame of a situation.

Thanks.

 

I know everyone is suggesting hoses etc and they’re correct that 30 year old hoses should be replaced. HOWEVER, I think you need to check all the connections from the work you previously did. For example, the air intake from the air cleaner to the throttle body. Is that connected securely/properly. My point is start with the basics. You didn’t have these issues prior to you doing that work.

 

You may have missed my last comment. We know where the air was getting in now. My friend cracked my lower-manifold during our injector replacement. I need a new lower-intake manifold. In a pretty bad situation.

 

Apologies. I missed that. Is that lower intake a big job? Wishing you the best of luck.

 

Not really a BIG JOB...just that we can't find a lower intake that we are sure is good. They aren't made for this gen anymore.

 

And you're sure it's cracked? It's just not something I've heard of before. I can picture crapping up the threads or something but not a crack. However, if you're certain, I would just grab one at a pick a part and clean it up. It isn't typically a part that goes "bad".

 

I am not certain, no. The shop that I went to claims that it was. I tend to trust them since they don't profit off of me. It is a price = parts kinda deal which is nice. What is a "pick a part?" Thanks for the help!

 

Junk yard where you can go in and pull the part off a vehicle. Then you can look it over and decide if you actually want it before purchase.

 

I can give it a shot. If you read my upper comment, I would definitely need the lower intake manifold...that isn't terribly hard to get ahold of...but I have NO idea how to remove a fuel line. If my guy can't fix the fuel line then I have an issue on my hands for sure HA. How do I know what engines match mine for the lower manifold? I know that Toyota T100 Pickups from the same year match...but so do other 3rd Gens between '96 and 2000. Anything else to look out for?

Thanks!

 

I wonder if the lower intake crack could be welded? Depends on what the aluminum alloy is, of course. But if you can't find a replacement it might be worth looking into.

Regarding the fuel line - there are shops around that could manufacture an exact replacement. Cost? Not sure.
But if the damaged section of fuel tube is removed without further damage (that includes not bending it during removal) the old fuel line could serve as an example for the manufacture of a replacement.

 

So what's happening with the fuel line? Leaking?
We are talking about the one on the frame?

 

How do you manage to crack that? Mistakes happen, but sheesh. Yeah, you will need to look at anything with a 3400 engine in it. Tacomas, 4Runners, Highlanders. Maybe even Camrys. These engines went into a bunch of cars.

 

I think Tacoma, 4runner, T-100
Highlander I'm pretty sure was MZ early then a GR.
No idea on Camry but I doubt it. 5vz was pretty much a truck engine.