Please Help: Extreme Loss of Power (@ 30% full power)

[mattkc16]

Hey Guys,

Im a new member to the forum and am having major powerloss @ the engine.

I took my 5th gen to the dealership (twice), and to a second mechanic and they haven't be able to nail down the issue. Currently the engine is operating at about 30% power. Initially this was an intermittent issue (about a month ago), but now it happens all the time. The truck is extremly slow to pull out, and can barely maintain speed on hills.

When the shops looked at it they checked clogged cats, mass air flow sensor, fuel pressure (pump/filter), fuel injection, plugs, among others. They are thinking the knock sensor is causing the engine to pull timing (decrease power). they did check the sensor and wiring harness and both have good continuity (i.e. no issues with them). The engine sounds perfect, they also didn't identify any knock or issue with the engine, but are recommending disassembly of the engine for a inspection to see if there are any issues withing timing, valves, pistons, etc....$$$. Does anyone have any recommendations of other things to check, or any applicable threads?

I recommended changing the knock sensor wire harness, but they said this is not likely to be the issue. Also, they didnt want to temporarily swap/pull the knock sensor to confirm 100% this is the issue.

Also, NO CHECK ENGINE LIGHT and no codes at the ECU. Any ideas?

 

[weeeee]

Hey Guys,

Im a new member to the forum and am having major powerloss @ the engine.

I took my 5th gen to the dealership (twice), and to a second mechanic and they haven't be able to nail down the issue. Currently the engine is operating at about 30% power. Initially this was an intermittent issue (about a month ago), but now it happens all the time. The truck is extremly slow to pull out, and can barely maintain speed on hills.

When the shops looked at it they checked clogged cats, mass air flow sensor, fuel pressure (pump/filter), fuel injection, plugs, among others. They are thinking the knock sensor is causing the engine to pull timing (decrease power). they did check the sensor and wiring harness and both have good continuity (i.e. no issues with them). The engine sounds perfect, they also didn't identify any knock or issue with the engine, but are recommending disassembly of the engine for a inspection to see if there are any issues withing timing, valves, pistons, etc....$$$. Does anyone have any recommendations of other things to check, or any applicable threads?

I recommended changing the knock sensor wire harness, but they said this is not likely to be the issue. Also, they didnt want to temporarily swap/pull the knock sensor to confirm 100% this is the issue.

Also, NO CHECK ENGINE LIGHT and no codes at the ECU. Any ideas?

Interesting how there are no CELs. I really don't think diagnosing a loss of power issue would entail an engine disassembly- pretty extreme.

Did they do a compression test or a leak down test when the plugs were pulled? That would tell you if there was a blown HG or something leaking past the rings or valves. If you haven't done this yet, I would strongly recommend it as your next step to rule out any mechanical issues.

A test drive or dyno run at load with a scan tool would be able to tell them if timing was being retarded for some reason. Was the timing within spec?

 

[1jzgte]

Hey Guys,

Im a new member to the forum and am having major powerloss @ the engine.

I took my 5th gen to the dealership (twice), and to a second mechanic and they haven't be able to nail down the issue. Currently the engine is operating at about 30% power. Initially this was an intermittent issue (about a month ago), but now it happens all the time. The truck is extremly slow to pull out, and can barely maintain speed on hills.

When the shops looked at it they checked clogged cats, mass air flow sensor, fuel pressure (pump/filter), fuel injection, plugs, among others. They are thinking the knock sensor is causing the engine to pull timing (decrease power). they did check the sensor and wiring harness and both have good continuity (i.e. no issues with them). The engine sounds perfect, they also didn't identify any knock or issue with the engine, but are recommending disassembly of the engine for a inspection to see if there are any issues withing timing, valves, pistons, etc....$$$. Does anyone have any recommendations of other things to check, or any applicable threads?

I recommended changing the knock sensor wire harness, but they said this is not likely to be the issue. Also, they didnt want to temporarily swap/pull the knock sensor to confirm 100% this is the issue.

Also, NO CHECK ENGINE LIGHT and no codes at the ECU. Any ideas?

\

Very odd.
What have u had done to the transmission? How many miles? tranny fluid change? Sounds like a possibly transmission solenoid.

 

[mattkc16]

It certainly is intersting. I'm actually taking it to a third shop, a friend of mine. The first 2 shops did not check compression, I will mention that to the 3rd shop. They did initially hook up a scan tool to check fuel consumption, but I didn't specifically ask if they checked timing. They did say the knock sensor had a higher output when compared to another 2010 4Runner they had on the lot (I'm told there are not specs for the knock sensors). They said that the knock sensor output could pull timing, but i don't think they actually checked the timing. If the sensor is seeing a knock, the compression check could identify an issue, I'll see what we can come up with on that route. Thanks for replying and let me know if u have any other ideas of things to check.

 

[mattkc16]

100k miles, I haven't had any transmission service (not recommmended in the manual till 120k. The tranny seems to shift fine, and downshifts to compensate for the power loss. Plus in 1st gear u can tell the power loss, so seems to be in gear fine.

 

[wfo9]

Are you under warranty? How many miles? What year?

This is where having a Toyota kind of sucks IMHO. The diagnostics tools are garbage from what I can tell. Dealers seem to have a heck of a time diagnosing drivebility issues when there are no codes jumping out and hitting them in the face.

I've resolved similar issues on other brands... And you can at least verify engine control parameters with a good high quality scanner and a road test. I'm just not sure if anything good is available for Toyota. I tried using tech stream once... it was such a pile of junk I gave up (but I was trying to use the cheapo version so it is possible the dealers have something better)

You need logs of Timing advance, load, fuel trims, A/F if available, mass air readings, MAP, Knock retard.... This data needs to be captured at a very high granular rate (again not sure if this is possible on a Toyota). ODBII rates and parameters typically won't cut it, but worth a try. Compare the graphs with a healthy engine or just look for anomalies. The knock retard would jump right out for example if that was the issue.

There are so many things that could be at the root of your problem.
- Bad injector
- bad sensor (maf, tp, knock, map, iat)

I sort of doubt it is anything internal on the motor from what you described.. but a tear down would be crazy... Leak down test would be fine...

 

[weeeee]

It certainly is intersting. I'm actually taking it to a third shop, a friend of mine. The first 2 shops did not check compression, I will mention that to the 3rd shop. They did initially hook up a scan tool to check fuel consumption, but I didn't specifically ask if they checked timing. They did say the knock sensor had a higher output when compared to another 2010 4Runner they had on the lot (I'm told there are not specs for the knock sensors). They said that the knock sensor output could pull timing, but i don't think they actually checked the timing. If the sensor is seeing a knock, the compression check could identify an issue, I'll see what we can come up with on that route. Thanks for replying and let me know if u have any other ideas of things to check.

Yep. If the shop has access to a leakdown tester that'll be the best way to do it since you can tell where the lost compression is actually coming from.

Important to note that if they are suspecting the knock sensor pulling timing, the only way to check would be under load, hence my suggestion to have a road test done with a scan tool hooked up. If you check timing at idle or under static testing the timing might be normal. But typically knock sensors should give off an error code when there's an issue.

 

[weeeee]

Are you under warranty? How many miles? What year?

This is where having a Toyota kind of sucks IMHO. The diagnostics tools are garbage from what I can tell. Dealers seem to have a heck of a time diagnosing drivebility issues when there are no codes jumping out and hitting them in the face.

I've resolved similar issues on other brands... And you can at least verify engine control parameters with a good high quality scanner and a road test. I'm just not sure if anything good is available for Toyota. I tried using tech stream once... it was such a pile of junk I gave up (but I was trying to use the cheapo version so it is possible the dealers have something better)

You need logs of Timing advance, load, fuel trims, A/F if available, mass air readings, MAP, Knock retard.... This data needs to be captured at a very high granular rate (again not sure if this is possible on a Toyota). ODBII rates and parameters typically won't cut it, but worth a try. Compare the graphs with a healthy engine or just look for anomalies. The knock retard would jump right out for example if that was the issue.

There are so many things that could be at the root of your problem.
- Bad injector
- bad sensor (maf, tp, knock, map, iat)

I sort of doubt it is anything internal on the motor from what you described.. but a tear down would be crazy... Leak down test would be fine...

Yeah. Honestly if the shop was recommending an engine teardown to dianose an unknown driveability issue I'd go to another shop.

 

[mattkc16]

It's a 2010 with 100k miles. No warranty, etc.

ill keep u posted on the compression leak check. I'm also hoping to swap in dummy knock sensors with the new shop to see if the problem goes away. This would point to a knock issue, then just need to identify what would be causing it.

 

[rigtec]

Hey Guys,

Im a new member to the forum and am having major powerloss @ the engine.

I took my 5th gen to the dealership (twice), and to a second mechanic and they haven't be able to nail down the issue.

Just curious... has the 'throttle body range of motion' been tested? Since (apparently) the engine sounds normal when running, and no CELs or trouble codes in the history logs were mentioned!

rigtec, cheers

 

[mattkc16]

Good point on no code, that's why my buddy/new shop says it's unlikely to be the knock issue. Thinking more likely a different sensor issue (maf, etc), but those should trip codes as well.

 

[mattkc16]

I asked Toyota to check the throttle position sensor, but after reviewing the work order on the receipt (I picked up the truck today) that wasn't listed. I'll check that out as well.

 

[Bumbo]

Amazing... the only time a Toyota doesn't throw a code is when it's actually broken.

Mine throws random codes all the time for fun when I am on the trail... drives perfectly fine lol.

Looking forward to hearing about a resolution OP. Hope you get it sorted out.

 

[wfo9]

Amazing... the only time a Toyota doesn't throw a code is when it's actually broken.

Mine throws random codes all the time for fun when I am on the trail... drives perfectly fine lol.

Looking forward to hearing about a resolution OP. Hope you get it sorted out.

I can't tell if you are joking or not. Mine throws no codes, but I would not be surprised at all if it did. All kinds of crazy stuff happens out in trail conditions with the the evap..... I'm guessing they were smart enough to turn most of those checks off in 4Lo.

 

[wfo9]

OP...

Although many Toyota dealers are horrible.... I think that is what you need to stick with. They are the only ones who would have the right diagnostic tools and resources available.. Unfortunately the skills of many of the folks that work there are not stellar when it comes to diagnosis.... Just have to find the right tech. Maybe ask for a good one in your area here...

Many times the assignments are random... Maybe try the... "I need your best engine control diagnostics guy....". It's not like the old days... Troubleshooting this stuff is more like troubleshooting a computer hardware glitch. You need software tools more than anything else.

And just an FYI, there is no base timing on modern engines. It's all individual coils controlled by the ECU. The knock sensors can have learning algorithms... so even if they are not currently detecting knock in a given load range.. it can still be pulling timing at a pretty high rate. I would try re-flashing or hard resetting the ECU in some way (only Toyota could do this) and see if that resolves the problem temporarily. That would at least clue you in if it is learning the problem over time or a bad sensor to start with.

 

[Leucifer]

Hey Guys,

Im a new member to the forum and am having major powerloss @ the engine.

I took my 5th gen to the dealership (twice), and to a second mechanic and they haven't be able to nail down the issue. Currently the engine is operating at about 30% power. Initially this was an intermittent issue (about a month ago), but now it happens all the time. The truck is extremly slow to pull out, and can barely maintain speed on hills.

When the shops looked at it they checked clogged cats, mass air flow sensor, fuel pressure (pump/filter), fuel injection, plugs, among others. They are thinking the knock sensor is causing the engine to pull timing (decrease power). they did check the sensor and wiring harness and both have good continuity (i.e. no issues with them). The engine sounds perfect, they also didn't identify any knock or issue with the engine, but are recommending disassembly of the engine for a inspection to see if there are any issues withing timing, valves, pistons, etc....$$$. Does anyone have any recommendations of other things to check, or any applicable threads?

I recommended changing the knock sensor wire harness, but they said this is not likely to be the issue. Also, they didnt want to temporarily swap/pull the knock sensor to confirm 100% this is the issue.

Also, NO CHECK ENGINE LIGHT and no codes at the ECU. Any ideas?

What's interesting to me is that you say the engine sounds perfect.....
If the engine is running through the rpm's fine, and sounds like it's running correctly, I would strongly suspect something in the transmission or the rest of the drivetrain.

You also mentioned it was intermittent and now is consistent. Last time I had a vehicle with a slipping transmission, it behaved the way you're describing.

The only other thing I'd take a hard look at is the ECU. Sure, it's not coding, but that may also be part of the problem.... that there's a problem and failing to code, in addition to causing the power loss.

 

[mattkc16]

What's interesting to me is that you say the engine sounds perfect.....
If the engine is running through the rpm's fine, and sounds like it's running correctly, I would strongly suspect something in the transmission or the rest of the drivetrain.

You also mentioned it was intermittent and now is consistent. Last time I had a vehicle with a slipping transmission, it behaved the way you're describing.

The only other thing I'd take a hard look at is the ECU. Sure, it's not coding, but that may also be part of the problem.... that there's a problem and failing to code, in addition to causing the power loss.

Good point, I did ask Toyota to check the tranny, and they mentioned that everything looks fine with it. It seems to be a loss of power at the engine, and not the drivetrain.

They did mention the ecu as an option. One option they recommended would be to temporarily switch the ecu with another and see if the issue resolves. Problem is, this swap is labor intensive as the key/ignition needs to be reassigned to the new ECU, and if this doesn't fix it the ECU would have to be reassigned again. There would be significant labor cost do diagnose this issue, with a low likelihood of resolution. Which is why at this point i didn't ask them to swap it.

 

[mattkc16]

OP...

Although many Toyota dealers are horrible.... I think that is what you need to stick with. They are the only ones who would have the right diagnostic tools and resources available.. Unfortunately the skills of many of the folks that work there are not stellar when it comes to diagnosis.... Just have to find the right tech. Maybe ask for a good one in your area here...

Many times the assignments are random... Maybe try the... "I need your best engine control diagnostics guy....". It's not like the old days... Troubleshooting this stuff is more like troubleshooting a computer hardware glitch. You need software tools more than anything else.

And just an FYI, there is no base timing on modern engines. It's all individual coils controlled by the ECU. The knock sensors can have learning algorithms... so even if they are not currently detecting knock in a given load range.. it can still be pulling timing at a pretty high rate. I would try re-flashing or hard resetting the ECU in some way (only Toyota could do this) and see if that resolves the problem temporarily. That would at least clue you in if it is learning the problem over time or a bad sensor to start with.

They did check the knock sensor and wire harness (They checked continuity), they didnt see any issue with the sensors themselves. They are thinking that it is truly a knock/ping (although they didnt hear any knock/ping).

One question i had is could the knock senor and harness look good from a continuity check, but still have wear, or another issue that is relaying a "knock". In other words, could a low/no knock look like a knock if the shielding to the wire harness is slightly damaged? They did check the wiring visibly and said this wasnt likely the cause, as there was no apparent/visible damage to the wire or sensor..

 

[wfo9]

They did check the knock sensor and wire harness (They checked continuity), they didnt see any issue with the sensors themselves. They are thinking that it is truly a knock/ping (although they didnt hear any knock/ping).

One question i had is could the knock senor and harness look good from a continuity check, but still have wear, or another issue that is relaying a "knock". In other words, could a low/no knock look like a knock if the shielding to the wire harness is slightly damaged? They did check the wiring visibly and said this wasnt likely the cause, as there was no apparent/visible damage to the wire or sensor..

stupid question, but surely someone checked, tried changing the plugs at 100k.

Knock sensors are just microphones... more or less. But they can pick up all kinds of false signals and can also go bad internally.

They are usually down in the valley cover and a bit of a PITA to swap in terms of labor. Sometimes there is a simple bypass harness you can rig up to see if that is the issue.

Most brands support a Knock Retard parameter that can be scanned under load. I'm just not sure about Toyota.

 

[philsey]

@OP Suggest you start a new thread in the General section, seeking a recommendation for a knowledgeable dealer in your area.

Post up your city and a link to this thread. [MENTION=66389]BlackWorksInc[/MENTION] may have some ideas.