Diagnosing P0115, PO300, P0302 & P0308 (1 Viewer)

[2001LC]

A 2000 LX470 239K miles, with oversize tires and trailer hitch (indicating towing heavy loads). Was brought to me for diagnosing rough running engine and CEL on.

Engine temp gauge read cold engine hot or cold. One time I though I saw t it read max hot, maybe not!

P0300, 302 & 308 are cylinder misfire codes. 300 general misfire whereas 302 & 308 are specific to cylinder #2 and #8.
The P0115 is Engine coolant temp sensor 1 circuit.
Antilock brake code C1201 was also set off.

Opening the hood and taking a quick look. I saw reservoir cap was not fastened down. Further inspection showed the pick up hose had landed on the shelve. This causes the hose to bend upward not reaching the bottom halve of reservoir. So act is if reservoir empty, when level of coolant near max mark. Thus not pulling coolant back into radiator during cool downs. This can result in air bubble in coolant system. On closed inspection, found radiator was about 2" inches low.

About 2 pints low, not to bad right. Wrong this can keep reservoir from function as designed. Even when pickup hose in properly reaching bottom of tank. Add old worn out radiator cap and we've a coolant system not doing it's job.

Noticed also that radiator is a Denso replacement. The top foam, side and bottom foam are all missing. This is very common after a radiator swap unless Toyota OEM is used or foam is swapped.

Also noticed the OAT temp sensor bracket was missing and sensor was just dangling and bouncing around. (I placed on frame to take picture.)

Further I noticed the idler tension pulley does not look right. The front guard plate has to much gap. None of the radiator hoses & clamps are OEM and none are pushed all the way on.

 

[2001LC]

In glancing around engine bay I also noticed; brake fluid was over filled and power steering reservoir was very low. Also some vacuum hoses had been replaced other with temp patched.

Taped to stop vacuum leak. Other ends of vacuum hose were very loose on van pump idle up.

Power steering Reservoir low indicates leak?

Both PS and DS steering rack output shaft boots very wet with fluid.

Brake res overfilled all to common.

 

[2001LC]

Not pictured is the water temp gauge sensor. Wire housing was missing and wire had been solider to sensor, but had fallen off. I was asked to fix water sensor and wire first before diagnosing DTC. Which I did by replacing, sensor, wire housing and soldiering on a new pigtail. My mistake, repairing first. As this would likely not likely have affect just cylinder # 2 an # 3 but could effect all cylinders. Also the radiator cap had not been replaced so I put on a new OEM cap. These are just some parts of what's effecting coolant system.
The highly prized 1282B FIPG was used to seal threads of new water gauge sensor.

Wire prepped to be solider.

1K watt heat gun

Shrink wrapped and solider in one.

New wire housing block installed.

 

[2001LC]

Once water gauge up and running I took on test drive. I monitored fuel trims and engine temp during test drive. First thing that jump out at me was bk 1 BK 2 running rich short term, and bk 2 long term being very corrected to leaned out at -11.7%. Temp also getting to high side for short drive.

 

[2001LC]

So what do we know. We know radiator replaced due to leak. Question is always how low did coolant get and for how long. With jimmy-rigged water temp sensor and wire off at this time. Operating temp was possibly not reading correct, or just not reading at all. So we've indication that make overheating a concern.

Number 2 & 8 cylinders misfire is often indication of bad coil. One that may not have failed yet, but is causing engine to run rough, which it was. Heat being the enemy of coils makes this a good bet.

Owner had replace # 8 coil with aftermarket and code did not change (DTC P0308). He then swap coils and code did not move. Number 8 cylinder continue to misfire regardless, not a good sign.

Aftermarket coils I don't care for, as it's a slipper slope when we depart from OEM on any part. I could see a number of non OEM parts had been used on this rig. Could it be we've a number of smaller issues adding up to operating issue?

I've also learned to pay attention to owner and what they've done to diagnose and repair. But regardless, I start from square one. We've many integrated system that can effect each other. So getting coolant systems in order made sense, this would get one DTC off the table, and then we'd see if rest came back (cleared all DTC at start of test drive).

Next up I want to get a good look at coils and spark plugs as I prepared for compression test. Normally I would just swap coils to start with. But since owner replaced and then swapped, I'd save that for later if nothing else found. I had a hot engine now, so moved fast to get a good compression test, which is done hot.

Pulling coils, I was slowed when #7 boot came apart and was stuck in tube on spark plug. Figures, #7 the plugs hardest to get at or see into tube. This interfered with spark plug wrench, until I could get free and vacuumed out. Luckily only slowed me by ~10 minutes, so engine still good and hot.

This is #7 after vacuumed and swabbed.

The valve cover gasket and tube seal had been replaced with aftermarket. I found a lot of oil on most plugs and in the spark plug tubes. I can't say, was oil just not cleaned up during reseal job, or had oil leaked back in. Top of that blue tube seal looks funny in that one dark spot.

The plugs were new NGK's and some coils.
I keep all coils and plugs in order when I pull them always, so I can look back, top LH is #1, bottom RH is #8
Most upper seals and boot were shot and boots broke up easily. Spark plugs thread were oily. Bk 1 all plugs were hand tight, bk 2 all plugs seem torqued in tight. Lots of oil and also dielectric grease on plug tops and in boots.

Larger chunk of coil boot still in spark plug tube #8 and/or in my vacuum now.

#6 spark plug thread had light kind of sliver colored oil substance on them. IDK!

A word on dielectric grease. It does not enhance or reduce current flow. It only guards against moisture induced oxidation. Whereas putting just a very small dab on spring up in coil may be okay, it's not necessary. The seal at top of coil and boot keep out moisture. The grease may even be counter productive, if to much added. As the grease may hold in and transfer more heat. This may reduce life of the boot and coil.

 

[2001LC]

Recap:
Owner stated:
He stated he tows and heavy trailer hitch indicates he pulls large trailer.
Radiator was leaking.
Coolant sensor wire housing busted and jimmy-rigged. This gives false signal to gauge and may also be used by ECM for adjusting fuel and timing. Toyota removed this water sensor in 2003 and went with just the one. It's unclear to me what all roll the old one played.
Coils are a mixed bag of old OEM with bad boots and newer after market coils.
All plugs are new and oily. Not sure if new leak or leftover from old oil not cleaned during head cover reseal.
Excessive dielectric grease on coil boots and plugs.
Engine had vacuum leaks.
PVC valves was stuck, which I freed. (not mentioned earlier)
Coils replace and swapped did not move the DTC of misfire.
Coolant slightly low and old radiator cap with new radiator.
Coolant reservoir not operating as designed.

Coolant issues and two cylinders on same head misfire. This may indicate head gasket bad or warped head. Inspection of head gasket did not reveal a leak. Nor oil residue in coolant, nor coolant in oil. All normal!

So up next was the compression test.

Not good.
# - PSI # - PSI , wet
1 - 185 2 - 115, 125
3 - 189 4 - 188
5 - 183 6 - 185
7 - 185 8 - 105, 115.

Leak down next up.

# 8 leak down, air heard coming from throttle body and number #2 spark plug tube. My air compressor has 120 PSI input to hose. Leak down will only takes 90 PSI and leak down shows 90% loss. With wet test showing a raise in compression of 10 psi, would indicate compression ring(s). But to see this much drop (90%) seems I'd seen better (high psi) wet if this all just rings. So heads and head gasket are in question. Air coming through throttle body and not heard at exhaust pipe or from oil cap (crank case) indicates intake valve(s).

#2 cylinder not as bad. But here again air sound come out throttle body.

So seems a heads are the issue. No leak found at head gasket and air sound indicates intake valves. Whereas the 10PSI raise in compression does indicates weak compression ring(s). I suspect I'd see some raise in most if not all cylinders wet.

So are valve(S) burnt with a hole or just not sealing well. I did scope, but could not see a hole. My scope is limited as to what can be seen. I could see difference in color across the intake valves. I also saw some minor scoring in a cylinder.

See where cross hatch marks (hone marks) are not crossing scoring.

Valves had vary color across tops and i see one dark spot I on edge of valve.

 

[2001LC]

So whats best courses of action now we know we've a bad head and some minor loss of compression at rings?

 

[Infinity00]

Good question. What are you thinking? How much does customer want to spend to fix? If it were me, I’d pull the heads and fix the valves.

 

[dace voit]

If the compression is that low in only two cylinders(instead of evenly low across the board) and you can determine that the rings are in fact leaking too much air, the engine is in need of rebuild. IF you can isolate the problem to the top end, then rebuilding one(both would be better) head can get the truck back on the road.

My concern is that this engine has been overheated enough to damage the head and possibly prematurely wear out the rings in two cylinders. Strangely, it's the outside cylinders that have issue. Aren't the inside cylinders more prone to damage from overheating?

The silver substance is possibly anti seize on the threads?

 

[2001LC]

Good question. What are you thinking? How much does customer want to spend to fix? If it were me, I’d pull the heads and fix the valves.

DIY would keep cost down. Then I suppose pulling both bad and good "heads" makes senses. Customers mulling option now.

If the compression is that low in only two cylinders(instead of evenly low across the board) and you can determine that the rings are in fact leaking too much air, the engine is in need of rebuild. IF you can isolate the problem to the top end, then rebuilding one(both would be better) head can get the truck back on the road.

My concern is that this engine has been overheated enough to damage the head and possibly prematurely wear out the rings in two cylinders. Strangely, it's the outside cylinders that have issue. Aren't the inside cylinders more prone to damage from overheating?

The silver substance is possibly anti seize on the threads?

Hard to say if engine was overheat, run hot or what. It could have burnt valves from vacuum leak. Could be poor oil & filter, air filter service history. I've not look at history!

Could be from coolant issues noted that it did run hot. I'm not seeing signs of overheating. But many hoses that have been changed makes it a difficult read. Hose will tend to be swollen if overheated.

Also head warp and gasket blow during over heating usually. I can't find coolant leak at head gasket, nor signs in oil or coolant.

So It's a difficult read on what happen. It not common to see bad valve and not in two cylinder at other end of one side. One thought is during spark plug job, head cover gaskets or starter job, some contamination entered the #2 & # 8 cylinders. That and long running vacuum leaks and coolant issues just was to much for even a 2UZ. Will never know for sure.

I was thinking anti seize or just mix of oil, dielectric and gasses. The color is not one I've seen before on spark plug threads. Again will likely never know.


So what coarse of action makes sense:

Head job:

If one head rebuilt I feel it will run okay. The slight raise in compression wet and mild scoring in some cylinders is concerning, but not overly. Also just doing one head and it will idle rough. So is extra cost of doing both worth the cost.

To pull a head and have mechanic shop rebuilt, replace with used or new OEM is not cheap. A well know Boulder mechanic did a head gasket job for $2,500, on a 05LC I was looking at years ago, prices are higher today. Dealer quoted $3K plus machine shop for bad spark plug threads (head job, not thread insert). If head bolts are replaced, the cost goes up.

Machine shop and add some valves, seats, seals and it's anywhere from $400 to $1K pre head.
Used head should be tested and milled. $200 to $600.
New OEM heads $2K wholesale.
Above prices are "off the cuff" as they say!

So estimated for just one head job is $3k to $4k.


Engine replacement:

Good Engine's aren't easy to find a from 00-02 series 100. Any non VVT will work, Japanese or US built. But a drop in 00-02 100 series will reduce part swapping and time.

Engine are $800 to $2k depending on miles and seller. Finding a good one can take time. Swapping is a time consuming job, in the $2k range for labor.

Engine swap is high on the list of consideration at this time.

 

[Infinity00]

Sounds like a no brainer if you can source a low mileage engine for 2k and 2k to swap in vs. that or more to do a single head. Then you’ve got everything covered from the rings, warped head and possibly burned valves.

 

[white_lx]

If the owner is looking for a budget fix, I would pull the bad head only. Then use a straightedge and feeler gauges to verify flatness of the head. If OK, then proceed.

Next inspect the valves and seats. If the seats are not damaged, then they can be refurbished DIY style with emery cloth and using the valve as 'tool'. Valves: re-grind if required, or new. After that lap the valves and re-install the head.

Most of this can be done DIY and the owner can save serious $ if he invests some time. Only if the heads are not salvageable, I would look at alternatives (engine, head, ...), but up to that point there is no expense - just time.

Could the wet compression results also be higher if some of the oil got around the leaky valve seats and made them seal a bit better?

 

[2001LC]

Sounds like a no brainer if you can source a low mileage engine for 2k and 2k to swap in vs. that or more to do a single head. Then you’ve got everything covered from the rings, warped head and possibly burned valves.

That does sound like a no brainier. But reliant on finding a good 2UZ from a 100 series. They 're not all good. Sometimes they (good engine) just pop up at right time. I should know first of week if any around here. Otherwise will look elsewhere. That is if I'm hired to find the engine.

Last time I hunted, was for a low mile VVT. I ended up settling on a 06 GX470 VVT that was recent kill. It been hit in the side, so hood was on sung. Once it hit the salvage yards, they pulled engine while indoors. So it never sat in the weather. The Lexus service history of it was perfect. Only bad was exhaust ports of head had some little pitting from rust belt type corrosion. That engine cost me $2,300 to my door as I recall. I spent maybe $500 more on seal, part ad what have you. Be a GX, I had to strip to naked long block and build back up.

Another local just did a engine swap, this last spring. He got burned on two or three engine in a row. Finally ended up having his mechanic rebuild one.

They'll be some extra time swapping new parts from old engine if we go this route. But I do thinking based on cost and some uncertain of how this engine was maintain and got in this condition makes swap they way to go.

If the owner is looking for a budget fix, I would pull the bad head only. Then use a straightedge and feeler gauges to verify flatness of the head. If OK, then proceed.

Next inspect the valves and seats. If the seats are not damaged, then they can be refurbished DIY style with emery cloth and using the valve as 'tool'. Valves: re-grind if required, or new. After that lap the valves and re-install the head.

Most of this can be done DIY and the owner can save serious $ if he invests some time. Only if the heads are not salvageable, I would look at alternatives (engine, head, ...), but up to that point there is no expense - just time.

Could the wet compression results also be higher if some of the oil got around the leaky valve seats and made them seal a bit better?

True; DIY, repair only what is damage (out of spec) and Macqyvering it, save cash.

But either current owner or a PO did something, that brought this on IMHO. Not knowing what, leaves a cloud on the engine internally. That is one reason a replacement engine may be best.

 

[dace voit]

What's the rest of the truck like? If it appears that it's not a well cared for vehicle then all this work sounds like a waste of time/money. Ultimately, it's the owners cash so they can do with it what they want. But if the rest of the truck was neglected, then other components can start to die down the line sooner than later, like transmission, etc...

 

[2001LC]

Good question Dace.

I've not inspected, but looks good. From TX, has minor front fender damage from bull bar, no rust. Owner feels it has good bones and at this point would like to put a good engine in. I've located 4 engine locally, all 100 series 98-99. At least three no front end damage (hood protecting from weather), one was just bought from auction (fresh kill) and will be available later this week. I'll need to DD each engine for miles, service history and such. Then inspect and scope. We may be able to get hot compression test on one or two, will see.

Looks well cared for. Our best guess as to why two cylinders have low compression is; Top of engine not cleaned before starter replacement. This is kind a big deal. What happens is, dirt drops into head intake ports, as intake manifold pulled off. It's a big deal most don't consider. When I was looking for a VVT engine last year for the Unicorn. I found one locally. When I went to inspect it, I found they sold the starter, so pulled intake manifold. They stuffed dirty rags into intake ports of head. I could see sand on heads above port, and in ports as I pulled rags. They said I was overthinking it! I said: Really, you think SO...bye, bye!

 

[dace voit]

They said I was overthinking it! I said: Really, you think SO...bye, bye!

HACKS!