Chasing a misfire that I can't solve. Help!

[G_Raw]

Okay so it started with what felt like a driveline vibration. I chased that...u joints, drive shaft, reset wheel base and driveline angles. No change. Then I started getting intermittent rough idles that would correct while accelerating. So I did valve covers, plugs, wires since my passenger valve cover was leaking. I cleaned throttle bottle and MAF at that point too. Oh plugs and wires were ngk.

This didn't correct things. Started getting intermittent P0300, P0303, and P0306. Found torn boot on cylinder 6 wire. Swapped coil #3 for coil #1. And installed all new OEM plugs and wire.


Still getting intermittent P0300, P0306, and P0303. So changed injectors.

No change. Swapped coil #3, previously #1, to position 5. No change.

Compression test results from today are...
Cylinder 1: 210
Cylinder 2: 195
Cylinder 3: 190
Cylinder 4 :195
Cylinder 5: 210
Cylinder 6: 180

All with in range but obviously cylinder 6 is borderline too low and well beyond the 15psi difference Toyota recommends.

Spark plug 6 definately looks like it has endured a misfire...

Photos are plugs 2,4, and 6.

Plugs 1,3,and 5 look like 2 and 4.


Still getting same 3 codes. To be fair I didn't change plugs when I did injectors. Should I change plug 6 due to the corrosion?

where do I go from here?

 

[Majkmichael]

What brand of injectors did you put in?

 

[brillo_76]

+ 1 on injectors.

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[LittleCaesar]

Plugs and wires first, then...

I would perform a leak down test on both those cylinders and go from there. Ever had a valve adjustment?

02 sensors original?

 

[G_Raw]

+ 1 on injectors.

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MotorWest injectors. I replaced all 6. I'd have a hard time wrapping my head around oem injector 6 leaking, replacing all injectors with MotorWest and then coincidentally still getting the same codes implying MotorWest injector 6 is bad...

[MENTION=69868]LittleCaesar[/MENTION]

Did plugs and wires twice...first ngk set, then Toyota set.

Toyota/denso plugs are in photo.

I could do a leak down but I'm not burning oil or coolant and got no white clouds out the exhaust...

 

[LittleCaesar]

MidWest injectors. I replaced all 6. I'd have a hard time wrapping my head around oem injector 6 leaking, replacing all injectors with MidWest and then coincidentally still getting the same codes implying MidWest injector 6 is bad...

[MENTION=69868]LittleCaesar[/MENTION]

Did plugs and wires twice...first ngk set, then Toyota set.

Toyota/denso plugs are in photo.

I could do a leak down but I'm not burning oil or coolant and got no white clouds out the exhaust...

Gotcha. The leak down test would show the engine’s ability to hold air. You may have one or two bad exhaust valves but can’t say from here since you have covered almost everything else and that plug doesn’t look too happy.

How did the plug from #3 look?

Brand of replacement injector, though I am assuming you had the misfire on the same cylinders before the change?

 

[G_Raw]

Gotcha. The leak down test would show the engine’s ability to hold air. You may have one or two bad exhaust valves but can’t say from here since you have covered almost everything else and that plug doesn’t look too happy.

How did the plug from #3 look?

Brand of replacement injector, though I am assuming you had the misfire on the same cylinders before the change?

Plugs on 3 is the same as 2 and 4 in the photos above. My theory is cylinder 6 is obviously misfiring and the ecu knows it but since coil 3 ignites cylinder 6, the ecu is trying to adjust the ignite causing the p0303 code. I'm changing plugs today again with OEM now that new injectors are in since I didn't do that when I put new injectors. I'm hoping the plug is so wrecked it's still causing a misfire and changing it will correct things.


And yes misfire was always on 6 even prior to injectors. Injectors are from motorwest. But used all Toyota o rings and gaskets on them.

Hoping it's not a piston ring or exhaust valve. Not looking forward to a motor swap or rebuild...

 

[LittleCaesar]

Good luck. I forgot to ask if there are any audible weird noises coming from around #6 or the like?

A scope with a mirror would be good to see if you have a cracked exhaust valve. Just finished replacing a head on an LS motor that had an exhaust valve that finally cracked after a serious initial day crack tick for some years.

Keep us updated.

 

[G_Raw]

Changed plugs today with OEM to get rid of that gnarly cylinder 6 plug. Drove for about 70 miles mostly freeway but some around town driving making one stop for groceries. Couldn't trigger a misfire. Scan gauge shows ecu ready with no pending codes. Still feel vibrations at driveline though...that's not to say it isn't a true driveline angle I haven't corrected. I don't feel the vibration at low speeds like I'd expect to with driveline angle issues. I still have a sneaky suspicion that the vibration is felt at highway speeds due to torque converter engaging at cruising speeds allowing the vibration to radiate through the driveline. So im not convinced I'm out of the woods with the misfire. But I'll keep driving and see if a code comes back for the misfire.

 

[Bad Luck]

Changed plugs today with OEM to get rid of that gnarly cylinder 6 plug. Drove for about 70 miles mostly freeway but some around town driving making one stop for groceries. Couldn't trigger a misfire. Scan gauge shows ecu ready with no pending codes. Still feel vibrations at driveline though...that's not to say it isn't a true driveline angle I haven't corrected. I don't feel the vibration at low speeds like I'd expect to with driveline angle issues. I still have a sneaky suspicion that the vibration is felt at highway speeds due to torque converter engaging at cruising speeds allowing the vibration to radiate through the driveline. So im not convinced I'm out of the woods with the misfire. But I'll keep driving and see if a code comes back for the misfire.

If the vibration is only felt when the torque converter clutch is locked up then that would lead me to believe torque converter failure. torque converter lockup occurs in 4th gear with overdrive on and in 3rd gear with overdrive off. How does your transmission fluid look and smell?

 

[G_Raw]

If the vibration is only felt when the torque converter clutch is locked up then that would lead me to believe torque converter failure. torque converter lockup occurs in 4th gear with overdrive on and in 3rd gear with overdrive off. How does your transmission fluid look and smell?

Trans fluid smells new and still red. 10k miles on it. It's not only at cruising speeds. Sometimes on deceleration or coasting down steep grades. My angles don't match they are off by .75 degree...which is enough to do it. I'd just expect to feel it at 15 to 20 mph but dont. I'm just saying when the torque converter locks in it seems to resonate the misfire more. Now it sounds like the slip yoke rattling on the out put shaft. And I should add the vibration has definately decreased since chasing and correcting ( hopefully) the misfire.

 

[G_Raw]

Misfire with code P0306 has returned. I'll try to do a leak down test this week. I don't have tools to do it. They look a little pricey...may just have a shop do it if it's cheaper.

 

[negusm]

Can a bad fuel pump starve fuel and cause these codes?

 

[G_Raw]

Can a bad fuel pump starve fuel and cause these codes?

I'm hesitant to believe it's a bad fuel pump still. The code consistently come up at cylinder 6 which shows low ( but within spec , but too low compared to other cylinders) compression. I'd assume a starved fuel pump would cause p0300 which is random misfire, seconded by various P030X codes depending which cylinder just got starved fuel.


My problem is P0306 always. Then when misfire long enough P0300 and P0303 show up. I'm operating under the assumption ( spark plug proves cylinder 6 misfire) that cylinder 6 is the problem child and the ECU starts to try and correct the issue which causes the P0300 and P0303 codes to come up since the coil on 3 connects to 6. Plug on 3 always looks good. Misfire doesn't follow changing of coil 3. Like most of us here I thought leaky injector. However now im suspecting a leaky valve, or bent valve perhaps...I'll see when I can get in to have a leak down performed.

 

[LittleCaesar]

Our local Oreilys has them for loan out along with compression testers. But not all Oreilys in the area do, so you may want to call around. I know that the local Harbor Freight has them for $25 at the moment but have heard that they don’t cut the mustard....

 

[Cogs87]

Misfire with code P0306 has returned. I'll try to do a leak down test this week. I don't have tools to do it. They look a little pricey...may just have a shop do it if it's cheaper.

I had this code a couple years back. It ended up being an open on the wire going to the injector. I accidentally damaged the wire when running another wire through a boot. Have you checked continuity?

 

[G_Raw]

I had this code a couple years back. It ended up being an open on the wire going to the injector. I accidentally damaged the wire when running another wire through a boot. Have you checked continuity?

Nope hasn't crossed my mind. I'm guessing ignition on multimeter set to volts test the tabs that plug in to the injector? I can tackle that this weekend when I do the vacuum hoses since a few are cracked...including the one that connects at back of drivers side valve cover ( it's near cylinder 6...hoping its just been a vacuum leak I missed).

 

[G_Raw]

injector plug checks out at 12 volts. Am I crazy here? I know normally clogged fuel filters and bad A/F sensors will throw codes for the. fuel system or the sensor itself normally. And when they cause misfires they typically cause random misfire ( a fuel filter has no control over which cylinder it starves, or and A/F sensor can only tell how much emissions the entire engine is putting out). However they do play a role in fuel mapping potentially. Therefore changing my old, possibly original, fuel filter along with my 10yr old, with unknown mileage in that time, A/F sensor may allow ECU to collect info that will correct what seems like a sporadic misfire.

One thing I should add that I may not have stated previously is I can now feel the shaking of the vibration at higher speeds and hold it steady till it triggers a CEL and code. But once I resume normal driving it smooths out some, but will still stumble occasionally at idles then correct again.

 

[19963.4lsr5]

You replaced everything and still the #6 missfire.

Do you have any antifreeze loss?


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[HiLife]

Is there a way to check for fuel volume? Wondering if cyl 6 is starving for fuel. Fuel line goes into the passenger side of the rail near cyl 5, then goes transfers over to the driverside of the rail. Cylinder 6 is the last cylinder to get
fuel from the rail before dumping through the regulator and returned back to the tank. Wondering if it's a ever so slightly sticking FR?
I'm just thinking out loud as you have tried almost every possible way already.