Rough idle - shaking, poor emisions (1 Viewer)

[matus]

Hi to all ,

I am experiencing an issue with engine performance resulting in poor emissions - high CO2. I do not get an DTCs nor MIL is illuminated.

I checked data via Techstream and also made graphs of O2 sensors as I was suspecting them to be faulty. I have attached graphs that I measured.

I noted that MAF sensor value seem to be lower that standard ( I found on this forum that the idle mass flow of the 2UZ-FE is around 4.8 - 5.7 gm/sec at idle.) Mine is significantly lower around 4. I have tested MAF sensor according to Toyota workshop manual and I get reading 3,9 OHMs by approx 10 degrees Celsius. As the reference values is for 20 C I am not able to confirm 100% if my measurement is OK as by 20 celsius it shoudl be 2,19-2,67 OHms.. Resistance should be increasing by lower temperature so I assume that MAF could be Ok.. But according to measured values is not?

I was first suspecting 02 Bank2 upstream sensor but then I noted that LTFT are around 20% positive what could indicate MAF sensor issue or vaccum leak.

Can someone confirm my theory that the MAF sensor is faulty and replacing it and thus getting 4.8 - 5.7 gm/sec at idle should solve the problem? I also checked if there is no restriction in air supply and replaced air filter, but without any change.

My LC is 1998 and not supporting misfire monitor per cylinder this could also indicate other parts poor performance , but spark plugs are new and coils don´t have any cracks on boots.

Thank you in advance for any help or advice.

 

[Doug H]

Hmm, those symptoms sound very familiar. The shaking sounds like it could be something as simple as a cylinder misfire; either a coil pack or sparkplug. Before doing anything else and with the engine running, try disconnecting the harness to your coil packs one at a time. You should notice a definite change in engine sound/roughness every time you do this. If one is bad, you won’t see any change when disconnecting it. The passenger side ones are a little harder to reach. Let me know what you find out.

 

[matus]

Hi, thank you for your advice. I will try and hope for the best. Will see

 

[matus]

I tried disconnecting coils but after each the engine performed worse so it is hard to tell which one could be soon gone. I also dont get any DTC s or Check engine light.

 

[Kamran Khan]

The easiest way to test if MAF is working properly is by disconnecting it while the car is idling, If the car engine shuts down that means the MAF sensor is working but if it continues to idle rough without the engine shutting down means your MAF is bad.

 

[matus]

Hi I measured resistance on MAF and compared to factory specs and those were not quite aligned. Also live data claims that it measures approx 3.9.

Anyway I will try to disconect it and see how the ebgine performs. I will send update soon

 

[2001LC]

Testing for vacuum leaks, is a good starting point when we see high LT fuel trims.

Often times I find a host of issues, not just one. Getting basics inline, is a first step. Which coolant system must be in perfect working order. Watching ECT (engine coolant temp) during normal stop and go drive is good practice. Which I do on my smart phone (dash water temp gauge, is near useless). Which is also what I use for fuel trim logging.

It may also be a good idea to do a compression test, to get a baseline on engine health.

MAF is a very sensitives instruments. I've seen, MAF seemly only a bit weak. Result in burning out a CAT. I've also seen, aftermarket (non Toyota MAF), result in issues and burning out CATs. Additionally, aftermarket parts wired into MAF, can result in issues. I've been getting incremental improvements in fuel trims, replacing MAF.

Cracks in coils is not a good sign. As it indicates excessive heat, which heat is the enemy of coils. But cracked coils can be fine and seemingly perfect looking coils, can be compromised. Looking for misfires with tech stream, can help find weak coils.


I had one, where all mechanicals of engine in top condition i.e. compression, coils, sparks plugs, no vacuum leaks, throttle body, etc. All good. Ran 44K & Chevron Techron through fuel system. Mostly looking to clean fuel injectors. But still, not be able to get long term fuel trims (LTFT) below 7% (target below 5%). As a PM, we replaced the fuel pump. Only then, did LTFT come into line (3%). We found deposit in fuel tank. Deposit's were, the larger remnants of rust. Fuel pump sock was dirty, and the worst looking crud from fuel filter I'd seen. Why rust in fuel tank? It's from old metal storage fuel station tanks, at some point in vehicle's history.
Note: I find, fuel trims readings/logs most useful, while cruising on flat HWY at ~65 MPH, holding gas pedal steady.
A look in Fuel tank, fuel pump basket.

Fuel filter

You'll also want to check health of CATs. This includes 02.

Consider using a CAT cleaning product.

Once confident engine running at peak, with good oil. I'd do a HWY run, holding 4,500 RPM. Do 3 minutes at ~4,500 RPM, then cruise at normal RPM. Then repeat for 5 minutes, than 7 minutes, than 15 minutes. This help burn out gunk from CAT's and off 02's. We start with short duration, to reduce risk of igniting excessive deposits of fuel & oil within CATs. I've found CATs temperatures, max-out around 4,500 RPM.

Also important. Avoid idling, which CAT run to cool and load up.

 

[matus]

Hi 2001LC,

thank you for your detailed email.

I will for sure need to check for vaccum leaks.

After cleaning MAF the performance got slightly better, but still there are minor shakes. I will try to find someone nearby and try to make swap if that helps.

I have replaced recently valce cover gaskets where I checked the coils for damage and crack and all were OK. Spark plugs and filteres were replaced with timing belt also recently. But this issue was there before...

I will check techstream for misfires - but I know mine is too old 1998 and ECU is not providing detailed information per cylinder.

I think I can also eliminate the fuel pump as this behavious is also when running on LPG.

I will have to check the CATS- maybe disconnecting exhaust pipe and checking it visualy may be a good way to start. And after that I will consider some CAT cleaner.

As there is quite a lot to check I will be updating my progress as time goes by

thank you

​

 

[2001LC]

Hi 2001LC,

thank you for your detailed email.

I will for sure need to check for vaccum leaks.

After cleaning MAF the performance got slightly better, but still there are minor shakes. I will try to find someone nearby and try to make swap if that helps.

I have replaced recently valce cover gaskets where I checked the coils for damage and crack and all were OK. Spark plugs and filteres were replaced with timing belt also recently. But this issue was there before...

I will check techstream for misfires - but I know mine is too old 1998 and ECU is not providing detailed information per cylinder.

I think I can also eliminate the fuel pump as this behavious is also when running on LPG.

I will have to check the CATS- maybe disconnecting exhaust pipe and checking it visualy may be a good way to start. And after that I will consider some CAT cleaner.

As there is quite a lot to check I will be updating my progress as time goes by

thank you

​

It is best practice, before anything electrical worked on. Disconnect the battery.
When cleaning and/or disconnecting MAF. Disconnect battery negative clamp first. Do not reconnect battery, until MAF clean, connected and a minimum of 20 minutes have past. This reset ECU.

No Cracks in coils, does not mean good.

Also it's important, where we get our parts, like coils and spark plugs and which ones. Many bootleg, look like real Toyota, Toyota Denso or Denso. The boot-leg parts market, is a billion dollar industry. Even buying from local parts stores, this junk gets into their inventory. A junk spark plug or coil, will often work fine for short while. Then go bad.

Looking into CAT, can be helpful. If clogged or burnt up. One way to do this. Is with a borescope ($100 up) or drain snake camera ($20). By removing the front o2 (A/F in VVT engine) sensor even rear sensors, and run camera in sensors port. Other test are back pressure (~1PSI) tested from front sensor port, and tail pipe gasses readings. Note: Some, with bad CATs, use extender on o2 sensor. The extenders, fool the EUC, but may not fool the emission test. A bad CAT needs replacing, once cause found and corrected.

I've seen misfire in 1998 LC, through Tech Stream. Where I detected a misfire coming from a coil that had been replaced, with aftermarket (non OEM) coil. This misfire would disappear as I watched. So I though just a glitch. But then I learned, issue video about shows. How tech stream has a glitch. I replace coil with a Denso, issue solved.

1998 LC 350K miles, tech stream reveled this newish non Toyota/Denso coil the issue.

 

[matus]

Hi

I prefer to buy parts by Toyota dealer when I am 100% that the parts wrong. They are not the cheapest

I have a endoscope camera so inspecting CATS mihht be easy . Just.. time is the issue

I ahve checked my TS for misfires and this feature is not there.

 

[2001LC]

So why does your tech stream read: Land CR. UZJ 2FE. ?
Which engine do you have? Can you post a picture of engine?

Your rear o2s are reading very different voltage. OS2 BK1 S2 .555V, BK2 S2 .005V. Is it about the same difference, over time?
I'll sometime, go in TS and control fuel trims (full rich than full lean). As I watch o2 sensors reaction.

 

[oakback]

My LC is 1998 and not supporting misfire monitor per cylinder this could also indicate other parts poor performance , but spark plugs are new and coils don´t have any cracks on boots.

I've had a misfire from a bad injector. Have you checked all your injectors? I placed a long socket extension against an injector with the engine running, and held the other end to my ear, and could tell which one was bad because it wasn't ticking. Easy/free way to check for that.

 

[matus]

HI 2001LC.,

the engine is 2UZ FE, see picture there are also the LPG setup..

and regarding the values.. I did a quick measureing of O2 as the engine was hot (87C) and see the graph below.. I am dont understand why there are values almost at 0 V when Idling after engine was revving for a while and also values above 1V are not OK I think. (02SB1S2)

 

[matus]

I've had a misfire from a bad injector. Have you checked all your injectors? I placed a long socket extension against an injector with the engine running, and held the other end to my ear, and could tell which one was bad because it wasn't ticking. Easy/free way to check for that.

Hi oakback,

thank you , I can check injectors the way you described, but assuming the performance issue is there also when running on LPG, ijectors should be OK as those inject gasoline. Just my thoughts..

 

[2001LC]

I ask: "So why does your tech stream read: Land CR. UZJ 2FE. ?"
Tech stream on USA models. Do not automatically find make, model and year except newer years. When I connect vehicle to tech stream, in say 1998-02, I must pick vehicle (make, model, year). Otherwise it may pick wrong, and I do not get all data available. In on years, l see in upper left hand corner of tech stream screen: Year, Model & engine (2007 LX470 2UZ-FE).

Your not seeing misfires is either:

• Your not picking correct vehicle as Tech stream connects.
• Your ECM is different than a USA model, modified or damage.
• Vehicle shipped/made to your region does not support. (not likely)

See upper left corner 2007 LX470 2UZ-FE

Seeing your, BK1 so different from BK2 sensor readings:
indicates issues after IM (intake manifold). This is not to say a pre head (MAF, throttle body, FI, FP, FPR or IM) not also (a secondary) issue. But pre head issues, tend to show up in both BK1 & BK2 at same time.

One bank issue:

1. IM gasket vacuum leak.
2. Compression issue (valves and or rings).
3. o2 sensors.
4. CAT. A bad MAF sensor, can take out a CAT fast. They get raw fuel soaking, and ignite burnning them out. Very often one side takes the worst of it, where they other may not have ignited.

By adjusting fuel trim (FT) to full rich than full lean. All sensor voltage should change. BK1 S1 & BK2 S1 about the same voltage, reversing with change in fuel trim. Same for Sensors 2 each bank.

I don't recall what voltage is high and which low during the change in FT . I've only done this in 06-07 2US-fe VVT. In those, sensors 1 is an A/F sensors (not an o2), and sensor 2 is an o2. They read differently. There are few guy here that have a very good understand of these voltage. Also many helpful youtube on reading this data.

Testing A/F sensors using Techstream

(This applies to '06 and '07 models only. Maybe also a few late year '05.) Air-Fuel Sensors can fail over time because of failed heaters. These failures are pretty obvious as the ECM will throw a P0051/P0052. However, they can also fail without it being immediately obvious (no CEL). Or...

forum.ih8mud.com

 

[matus]

Hi
I have tried multiple versions of TS and also tried to connect other toyota models and it always chose automatically the model. I have European version which may be different. I can only chose if it is Landcruiser or Lexus and then some production periods (3 or 4 options). Engine is loaded automatically.


I did compresion check and all cylinders had about the same value. I will check both Cats condition and start from there.

Is there any way to check IM gasket? Spraying brake cleaner around and see if RPMs will not increase?

When I was playing wth injected volume recently when I added more fuel the performance got slightly better. Could indicate MAF reading wrong values or a vacumm leak?

Thank you

 

[2001LC]

MAF sensor is very sensitive. If any doubt it's not work perfectly, replaced it. They'll kill a CAT fast.

 

[matus]

Hello again,

so I replaced MAF sensor, and after few days of driving no change in engine performance...§
Next thing will be inspecting CATs.. and O2 sensors..

lets see if there will be any improvement.

 

[matus]

Hello again,

so there is a slow progress . I had the car smoke tested for leaks. One vacum hose had a little crack and there were 3 minor leaks that were fixed. One of them was on the LPG kit. so the car will go for inspection of the LPG. Hope the results will get better after that.