Another Misfire Thread - LX 470

[JlinLX]

Hello everyone.

About a week ago I purchased a 2004 LX 470 with a significant radiator leak. Because of the risk of overheating I wasn't able to run the engine for more than a few minutes but I thought it sounded fine at the time. The truck had an excellent service history – dealer maintained from 2004 to March 2020 – which convinced me to pull the trigger.

After I swapped the radiator I started the engine and it began to run quite roughly. The CEL began flashing and both VSC lights turned on. When I plugged in my scanner it came up with the codes: P0300 - Random/Multiple Cylinder Misfire Detected, P0302 - Cylinder 2 Misfire Detected, P0304 - Cylinder 4 Misfire detected, & P0306 - Cylinder 6 Misfire Detected.

I assumed this was due to bad ignition coils so I swapped the coils from cylinders 1, 3, & 5 with the coils from cylinders 2, 4, & 6. I also replaced the spark plugs in the misfiring cylinders but the problem and codes persisted. When I revved the engine to ~3K rpm the CEL and VSC lights turned off but would come back on when I let it back to idle.

It seems like the truck has been sitting quite a lot for the last seven months or so, the March 2020 dealer service was at 203,148 miles and it currently sits at 204,964. While I was swapping the coils I found a rodent nest under the intake manifold.

Are these misfires usually caused by electrical issues or could it be fuel/air-related? I would like to exhaust all the easy options before I start tearing apart the wiring to the coil packs to look for mouse nibble marks.

Any ideas or help would be greatly appreciated!

 

[ramangain]

Knock sensor?

 

[JlinLX]

Knock sensor?

Its not throwing any knock sensor codes but that would make a lot of sense, the nest was right on top of the sensor.

 

[ramangain]

You wouldn't be the first to have this issue

 

[ramangain]

Might as well think about rehabbing the starter motor and contacts while the manifold is off too.

 

[JlinLX]

Might as well think about rehabbing the starter motor and contacts while the manifold is off too.

It would give me a chance to get the rest of the nest out too. Thats a tight spot down there.

 

[ramangain]

You could always use lighter fluid and burn the nest out of revenge ....

 

[JunkCrzr89]

What are engine temps? Hopefully not a head gasket...but 3/4 cylinders all on the same bank is often HG, which wouldn’t exactly be surprising considering the prior radiator issue.

 

[MJK]

How did the plugs look when you pulled them? Oil milky? Did you test the coolant for exhaust gas, or pressure test it? Can you snake a camera or mirror down to see the knock sensor wires?

More info please.

 

[2001LC]

When I see leak during inspection, it always concerning. Why, because no way to know how long it's leaked, or how low the fluid went at any given time.

I'd be looking very hard at head gasket, from below and above. Then compression test and coolant system pressure test.

PM me if you like to bring by. I can look over and inspect head gasket.

 

[JlinLX]

How did the plugs look when you pulled them? Oil milky? Did you test the coolant for exhaust gas, or pressure test it? Can you snake a camera or mirror down to see the knock sensor wires?

More info please.

When I pulled the plugs they were dry but covered in a little soot. The plug from cylinder 1 was a slightly cleaner than from the plugs from the misfiring cylinders (2, 4, & 6). I can post photos this afternoon when I get back to the truck. I am going to try to pressure test the cooling system and test compression today if I can find the tools.
As far as the knock sensor goes, its pretty tough to see anything up under the manifold, I'll look into getting a snake camera as well.

 

[JlinLX]

When I see leak during inspection, it always concerning. Why, because no way to know how long it's leaked, or how low the fluid went at any given time.

I'd be looking very hard at head gasket, from below and above. Then compression test and coolant system pressure test.

PM me if you like to bring by. I can look over and inspect head gasket.

I completely agree, it was risky and I may be paying the price! As far as head gasket inspection goes, am I just looking for dried coolant around the heads or are there other telltale visible signs?

 

[ramangain]

Chances are pretty good it is an issue with the knock sensor wiring. Might as well prepare to pull the intake manifold .... rodents like to munch on those wires.

 

[JlinLX]

Chances are pretty good it is an issue with the knock sensor wiring. Might as well prepare to pull the intake manifold .... rodents like to munch on those wires.

I certainly hope its a wiring issue so I don't have to deal with the head gasket!

 

[2001LC]

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[2001LC]

I completely agree, it was risky and I may be paying the price! As far as head gasket inspection goes, am I just looking for dried coolant around the heads or are there other telltale visible signs?

All depends on what you paid. I'm on my second with bad engine. The first was really sweet The Unicorn

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I look for dry crust reddish (Toyota coolant)externally around head gasket. In the pre VVT, it's possible to look at 90% of lower and upper areas of head gasket, with just a flashlight. All shielding and air pipe off.

 

[JlinLX]

Here is an update of what I've found over the last couple days:

- I bought a bore scope and checked the wiring to the knock sensors, even though the mouse nest was right on top of the sensors I couldn't find any chew marks and the wiring looked good.

- I found a white, viscous substance on the inside of the oil cap.

- I found exhaust gas in the cooling system

At this point I am assuming that it is a bad head gasket, although I haven't noticed oil in the coolant as I've been flushing out the old stuff. I also haven't noticed any water in the oil or white smoke coming from the exhaust.

 

[MJK]

Yep, HG. Sorry to hear the bad news, but at least you know.

 

[ramangain]

Yeah, I was rooting for the knock sensor wires; it would have been an easier job

 

[JunkCrzr89]

Yup, leaky HG...hopefully not cracked head. You Should get in touch with @2001LC for advice about proceeding forward. He’s local to you and has an extraordinary wealth of knowledge about 100s, the 2uzfe engine, and blown HG.