High mileage misfire 5vz-fe

[airkhin]

Sorry in advance of long post. '99 Sr5 Sport 5vz-fe

Feeling pretty stumped with this one and would like some insight. Very recently have started to get a misfire P0300 (random cyl), P0303 (cyl 3) P0306 (cyl 6), ONLY after warmup and restart car.

On cold (overnight), starts runs like a champ, not a hiccup, drive over 40+mi and never an issue. No cel no hesitation at all.

Restart car after warm will begin to hesitate. if clear the code (scan gauge) cyl 6 is first code to begin pending. after quite some time will begin to show cyl 3 misfire as well.

When it is misfiring / stumbling during driving - cel is flashing. Only codes that ever register are above.

Miles on car 342k+.

Within the last 6kmi -

Leak down test even across the board.
New NGK Plugs / Wires.
Swapped coil packs around.
Swapped injectors around, cleaned all best as possible.
New TPS.
Both upstream and downstream sensors (cali emission truck)
Replaced any vac line possible.
Cleaned maf
Cleaned Throttle body / runners/ intake tract.
Seafoam in gas tank,
New fuel filter / air filter.
Air raid intake (to eliminate any possible source of potential cracked hoses)
Previous owner had timing belt replaced at 278k (per the sticker) but noticed crank pulley bolt was not torqued to spec when doing leak down. Pulley is now torqued properly.

Just would like to get any insight or ideas what might be causing the issue. Feels as if its a switch or sensor thats causing the misfire. One instance was at a stoplight misfiring , and then it evened it self out and ran perfect for 20+mi before began to misfire again. Greatly appreciated.

 

[davidch]

Swap coils, clear codes, and see if the thrown codes move to another cylinder pairing, eg 1-4 or 2-5.

 

[Black798]

Ive never heard of this happening on a 5vzfe specifically but have had it happen a few times on other cars when a coil pack starts going and will randomly shut off under heavy load or just sitting at a light. So you could have one or more coil packs on their way out and they are only failing intermittently. May be worth looking into

 

[airkhin]

sorry completely forgot to mention already tried swapping around the coil packs multiple times.

 

[Black798]

I would pick up a new coil pack and try cycling that through. Even if you've tried with your existing packs, all three could be bad so you may not notice a difference. But if you can confidently rule out your coils and plugs I would then point to the injectors. Its odd since you've already checked basically everything that could be causing it.

 

[stir_fry_boy]

Also the coil pack boots could be to blame.

 

[will2k3]

Same issue

I have the same symptoms: 230k, P0300, P0303, P0306 randomly on warm start, misfires that gets progressively worse until flashing CEL and stumbles until shuts off. For frequency reference: the above symptoms happened three times: Mar 24, Sep 24, then Jan 25.

Mar 24 resulted in a tow after multiple restart attempts and coil swaps over two days, then it started and ran fine the moment it came off the rollback at the shop. Sep 24 it fixed itself after a few hours of sitting, then Jan 25 it refused to ever restart and was towed to the same shop.

The Jan 25 event: I tried swapping over a good igniter from another 5vz, put a test light on the three coil leads and got a light when cranking, tried a known good older coil on 3/6. At the shop now, no word yet, and luckily (I think) the symptoms persisted so hopefully the diagnostic tool can give some feedback.

Between problem events I changed the following in hopes of preventing the symptoms: New plugs, wires, all three coils, all 6 injectors. Drove over 10k miles in the midst of those parts swaps, flawless, no issues besides the dates mentioned.

Was there ever a resolution to this back in 2016?

 

[will2k3]

Responding to myself: Figured it out

Well, this turned out to be more interesting than I imagined. I'd love to start a new thread but I can't yet as a new member.

As detailed above, issues with no resolution. Took it to my new trusted shop (Ironwood Automotive) and as before, the symptoms resolved so no evidence to point the issue, nothing to diagnose. Shop didn't even charge me because there was nothing to fix, good people there.

Took the 4runner home, and it displayed the symptoms again, but this time resolved on both occasions. I also discovered that by revving the engine I could make the stumble go away. Confusing solution, but it worked in both cases. Still no CEL, no evidence on the scanner while running and exhibiting symptoms of what sensor might be causing issues.

One part I hadn't replaced was the fuel pressure regulator. I didn't have any common bad FPR symptoms but I was in old 4runner parts cannon mode so I stripped down the intake to get to the fuel rail and looked into each of the intake valve ports with a flashlight because having built an engine before, it's prudent to inspect places you commonly can't see when you have the chance.

This is when it got interesting.

Inside the cylinder number 6 rear-most intake valve port......was a nut.

A stainless steel, 14mm flanged nut that looked like it had been in a rock tumbler for 10,000 miles. Which is exactly the distance I had driven it since Ourisman Toyota in Richmond, VA replaced (poorly) my valve cover gaskets. At first I though that surely I had somehow dropped it in....but no, it had 100% been in there for a while and now I was experiencing a confusing mixture of emotions as I realized that this had been my issue all along and as I went through old photos to confirm the sequence of events a year ago:

1) None of my symptoms existed before the valve cover gasket change at Ourisman and I had the symptoms before the second shop also had the intake off. New to me vehicle so I assumed the PO had the issue and didn't disclose.
2) the intermittent symptoms started a week after I got the vehicle back from the dealership.
3) Ourisman broke the valve covers on install and had to take the vehicle back and install new ones (free, they admitted fault)
4) they didn't replace the half-moon cam cap sealant so the valve covers still leaked (the job was re-done by new shop)
5) they didn't fix a t-case output leak correctly (new shop had to fix it)
6) they hooked up the evap lines wrong which caused a highway stalling incident when the purge test ran (I have another 5vz and easily saw what was wrong there
7) they hooked up the pcv line to the FPR vac line and the intake air for the evap purge to the post-throttle body PCV so there was a direct air line bypassing the throttle body. When I fixed it the computer and IAC had to relearn the lack of massive air leak and would barely idle for a few starts, took about an hour of relearn.
8) THEY LEFT NON-TOYOTA HARDWARE IN THE INTAKE.

Toyota doesnt use stainless, the nut is too large to match up to anything in the engine bay. These idiots did so much wrong, in spite of the Ourisman (I'm going to keep mentioning them) service writer saying they had their master tech on it.

I mean, shame on me for trusting the dealer, right? I'm not a conspiratorial person but there are times when I wonder if any of this was intentional? To be really clear, I was super nice and patient (vehicle wasn't my DD at the time) the whole time so I'm confident there was never a "customer is a a-hole" whisper. Maybe a "make him regret this old car so he buys a new one"? Tough chance. Gen X here so kiss my a## if you think I don't love cars from when I was in my 20s.

At any rate, in spite of my ability to start new threads in the Jeep forums, I'm new to the 4runner forum (DD is a 04 Tacoma), but I'm hoping to one day reach my 10 posts so I can make sure to warn people in Richmond to never go to Ourisman Toyota for service since they are incompetent or stupid or manipulative or something. But this is why I don't trust other mechanics. Sometimes I just don't want to do the work or I get confident that they'll do it right, and then they don't. Or they do more damage than I started with.

And if I didn't know what I was looking at or know how to fix some of this, I'd be sunk and they'd take more of my money to fix it...again...maybe. If someone who truly didn't know how to address incompetent work was the vehicle owner, they'd be at the mercy of the shop and would just pay more and more.

Shame on you, Ourisman.

 

[Endlessblockades]

Wow - not the reason I expected!

 

[brillo_76]

Well, this turned out to be more interesting than I imagined. I'd love to start a new thread but I can't yet as a new member.

As detailed above, issues with no resolution. Took it to my new trusted shop (Ironwood Automotive) and as before, the symptoms resolved so no evidence to point the issue, nothing to diagnose. Shop didn't even charge me because there was nothing to fix, good people there.

Took the 4runner home, and it displayed the symptoms again, but this time resolved on both occasions. I also discovered that by revving the engine I could make the stumble go away. Confusing solution, but it worked in both cases. Still no CEL, no evidence on the scanner while running and exhibiting symptoms of what sensor might be causing issues.

One part I hadn't replaced was the fuel pressure regulator. I didn't have any common bad FPR symptoms but I was in old 4runner parts cannon mode so I stripped down the intake to get to the fuel rail and looked into each of the intake valve ports with a flashlight because having built an engine before, it's prudent to inspect places you commonly can't see when you have the chance.

This is when it got interesting.

Inside the cylinder number 6 rear-most intake valve port......was a nut.

A stainless steel, 14mm flanged nut that looked like it had been in a rock tumbler for 10,000 miles. Which is exactly the distance I had driven it since Ourisman Toyota in Richmond, VA replaced (poorly) my valve cover gaskets. At first I though that surely I had somehow dropped it in....but no, it had 100% been in there for a while and now I was experiencing a confusing mixture of emotions as I realized that this had been my issue all along and as I went through old photos to confirm the sequence of events a year ago:

1) None of my symptoms existed before the valve cover gasket change at Ourisman and I had the symptoms before the second shop also had the intake off. New to me vehicle so I assumed the PO had the issue and didn't disclose.
2) the intermittent symptoms started a week after I got the vehicle back from the dealership.
3) Ourisman broke the valve covers on install and had to take the vehicle back and install new ones (free, they admitted fault)
4) they didn't replace the half-moon cam cap sealant so the valve covers still leaked (the job was re-done by new shop)
5) they didn't fix a t-case output leak correctly (new shop had to fix it)
6) they hooked up the evap lines wrong which caused a highway stalling incident when the purge test ran (I have another 5vz and easily saw what was wrong there
7) they hooked up the pcv line to the FPR vac line and the intake air for the evap purge to the post-throttle body PCV so there was a direct air line bypassing the throttle body. When I fixed it the computer and IAC had to relearn the lack of massive air leak and would barely idle for a few starts, took about an hour of relearn.
8) THEY LEFT NON-TOYOTA HARDWARE IN THE INTAKE.

Toyota doesnt use stainless, the nut is too large to match up to anything in the engine bay. These idiots did so much wrong, in spite of the Ourisman (I'm going to keep mentioning them) service writer saying they had their master tech on it.

I mean, shame on me for trusting the dealer, right? I'm not a conspiratorial person but there are times when I wonder if any of this was intentional? To be really clear, I was super nice and patient (vehicle wasn't my DD at the time) the whole time so I'm confident there was never a "customer is a a-hole" whisper. Maybe a "make him regret this old car so he buys a new one"? Tough chance. Gen X here so kiss my a## if you think I don't love cars from when I was in my 20s.

At any rate, in spite of my ability to start new threads in the Jeep forums, I'm new to the 4runner forum (DD is a 04 Tacoma), but I'm hoping to one day reach my 10 posts so I can make sure to warn people in Richmond to never go to Ourisman Toyota for service since they are incompetent or stupid or manipulative or something. But this is why I don't trust other mechanics. Sometimes I just don't want to do the work or I get confident that they'll do it right, and then they don't. Or they do more damage than I started with.

And if I didn't know what I was looking at or know how to fix some of this, I'd be sunk and they'd take more of my money to fix it...again...maybe. If someone who truly didn't know how to address incompetent work was the vehicle owner, they'd be at the mercy of the shop and would just pay more and more.

Shame on you, Ourisman.

So you literately had a nut bouncing around in the on top of a intake valve? I cant say I have heard of this one. Granted, must people tape off the intake ports ASAP so things like this do not happen. Great job in finding it. Really explains why it was so hard to resolve. :-(