No power at high RPM

[LX470 AUS]

My LX470 seems to run quite well, it has quite a bit of power between idle and 3000 RPM, but over 3000 RPM it doesn't seem to accelerate any more.
If I'm going up a slight hill in second gear (foot flat) ill get to around 80 KPH (50 MPH), the engine will be doing around 3500 RPM, and it will feel like there is no more power. If i keep the foot flat, it will slowly gain rpm and speed until it changes into 3rd, then it will accelerate better (because in lower rpm range).
I am wondering if this is normal for these engines? to have all the power between 1000-3000 rpm. But it seems odd that it has almost none above 3500.
I have ordered a OBD cable online, so I will have a look at the ECU parameters when it arrives.
I am also getting pretty poor fuel economy, 20-22 L/100Kms (~10MPG) combined highway and a bit around town, not much heavy traffic though.
Vehicle details:
1998 LX470, Australian, no bull bar, no 3rd row seats, 285/75 16 Maxxis Bighorns, pacemaker extractors, twin 2.5 into 3 in exhaust, no cats.
Also I just replaced spark plugs, cleaned MAF sensor and throttle body.

Thanks for any input.

Stew

 

[Matt037796]

Catalytic converter ?????????

 

[Matt037796]

Sorry brain -/:;@@" not cats..

 

[Actualeyes]

Fuel restriction? Maybe even the filters in the tank are clogged up... I know in my old 105 diesel this had happened - dust gets into the tank and eventually clogs up the filters on the fuel inlet. PIA to get to mind you!

 

[LX470 AUS]

I forgot to say, the vehicle has 210,000 kms (130,000 mi) on the clock.

 

[LX470 AUS]

An update on this issue, the problem seems to be getting worse, the vehicle seems to be struggling to stay at 100 kph when on the open road (on the flat), fuel consumption is over 20L/100KM (10MPG). Idle has started becoming slightly rough, not surging, but causing vibration in the car.
Checked so far:
-I have cleaned the throttle body with TB cleaner and a rag, looks all clean,
-cleaned the MAF with MAF cleaner twice,
-replaced all spark plugs,
-reset ECU,
-checked air filter (looks almost new),
-ran injector cleaner in two tanks of fuel,
-replaced ECU temp sensor
-checked thermostat (all within spec)

Here is a shot of live data from techstream once at operating temp:

No error codes are showing up, no CEL. I am inclined to think it is a coil pack beginning to fail, but surely this would show an error code. Has anyone experienced coil pack failure without CEL or error codes showing up?

One thing to note, when I changed spark plugs i noticed the previous owner didnt tighten the plugs when last changed, a couple of them were pretty loose (could undo by hand). On these plugs, there was evidence of burning on the top (white ceramic part) of the plug, and also slightly on the coil pack.
Apart from loosing a bit of compression, do you think this could have had any effect on the coil packs (exposure to high temps)?

I'm struggling to think of what to do next in the diagnosis process. I might buy a new coil pack and rotate it through the cylinders to see if there is a failed one present.

Any other ideas?

 

[LX470 AUS]

Also to note: when the car is not running, and I put the acceterator pedal flat to the floor, the live data on techstream shows the throttle position to be 80%. I would have though this should be 100%?
Looking at the above data, the ignition advance is at 8 degrees, does this seem normal or a little low?

 

[PADDO]

Also to note: when the car is not running, and I put the acceterator pedal flat to the floor, the live data on techstream shows the throttle position to be 80%. I would have though this should be 100%?
Looking at the above data, the ignition advance is at 8 degrees, does this seem normal or a little low?

My hot idle ignition advance falls in the 13 to 15 degree range, so yours seems low at 8 degrees. Have you checked for vacuum leaks, restricted fuel flow (blocked filter) and how are your fuel trims? Last time I checked my LT trims they were around -1% and -2.5%. I've been told anything between 0 and -5% is to be expected.

Sent from my iPhone using IH8MUD

 

[LX470 AUS]

Is the ignition timing advance controlled by a vacuum actuator? I have a vac test kit, but am not too sure how to go about testing for vacuum leaks.
Also, are the fuel trims readable through techstream?
Thanks

 

[OregonLC]

With OBD (since 96) ignition advance has been solely controlled by the ECU.

 

[PADDO]

Is the ignition timing advance controlled by a vacuum actuator? I have a vac test kit, but am not too sure how to go about testing for vacuum leaks.
Also, are the fuel trims readable through techstream?
Thanks

Yes you can check fuel trims with techstream, engine and ECT live test, you can also check individual cylinder misfire counts, O2 sensor ccts and outputs, and a lot more. Stating the obvious, something isn't right if you're having trouble maintaining 100kmh on flat ground. Do you have transmission slippage when it should be locked up? Good luck.

Sent from my iPhone using IH8MUD

 

[LX470 AUS]

After work today i took a temperature reading of each exhaust outlet using a temperature gun, they were all pretty similar to each other, around 200-250 degrees C. I was hoping I could narrow down a cylinder that wasn't burning properly and test the coil pack by switching it with another.
I had another took at the TB, tried cleaning it some more, but it was pretty clean.
I noticed with the engine off, and the ignition on, a funny sound from the throttle body, it sounds like an electric motor trying to turn, but not being able to. When I depress the accelerator, it goes away/changes the sound, but comes back once foot is off accelerator.
Is the throttle controlled by an electric motor? Is this a normal sound?

I couldnt seem to see the fuel trim parameter on tech stream, it is in the engine and ECT live tab?
Not too sure about the transmission, replacing AT fluid is on the list of things to do.
On my next things to try list are:
A - get new coil pack and trial in each cylinder to see if there is one failing one present.
B - replace fuel filter
C - replace transmission fluid

 

[lx470cinci]

Tranny slippage:
From a stop, floor it. Does the engine race above an equivalent steady state RPM? How does it shift? Is it crisp or does if 'flare' and float down to the next gear. If it 'flares' your tranny is slipping. Replaced my tranny at 125k miles.

Cat's plugged? Here is how to check:
http://www.youtube.com/watch?v=IzyvL5tQLzU

How to check for bad coil:
The poor man's way (my favorite) for finding bad ignition coil packs is to simply pull it off plug. Put an extra spark plug in the coil and make sure the metal threads of the plug are against the block. Have an assistant crank the engine. You should get very bright sparks! Check all 8 packs. If you get little to no zap on one of them then you found the culprit.

Does the exhaust smell like raw gasoline when you first start it up (catalytic converters cold)? If so, this would point to an ignition problem and dumping in gasoline which is not burnt. If you run the engine a moment when cold and then pull the plugs you might smell gasoline on the spark plug with the ignition problem.

Good Luck,
Greg

 

[LX470 AUS]

The tranny doesn't seem to be slipping, it doesn't 'flare', and it shifts fast and tight.
I have no cats, the previous owner removed them. The 98 model in Australia doesnt come with O2 sensors, they only added them from around 2002 I think (i checked this with toyota).
I had replaced all the plugs around 1000 kms ago, so today I pulled out all the plugs to see if any of them looked as though they hadn't been firing. One of them looked a slight bit less used (not so burnt), all the rest looked similar to each other. The one that is a little different has an aftermarket coil pack attached to it (not a Denso), so im hoping this was replaced a while ago with a cheapy that isn't doing its job properly. Im not convinced this is the problem though.
Anyhow, I ordered a new coil pack from Toyota, will get it tomorrow and see if it makes a difference. If not its always good to have a spare coil pack in the tool kit.
I also ordered a fuel filter, so I will replace that too.
I pulled off clips to a couple of the coil packs (one at a time) to see if it changed the idle at all, it didnt seem to make much difference to the idle, but I could smell raw fuel when unclipped.
Ill let you know how tomorrow does. Keen to get to the bottom of this..
On another note, I adjusted the tortion bars to get the front AHC neutral pressures in spec, the ride seems a lot nicer now. I ordered some 15 mm coil spacers to reduce pressures in the rear.
Thanks for the help
Stew

 

[lx470cinci]

Using techstream, I wonder if you can check the function of the crank angle sensor. If your timing was being retarded too far at high RPM, that would de-power the engine. Another item which could cause the timing to overly retard is a bad knock sensor.
Cheers,
Greg

 

[2001LC]

I don't know if this will help, but some years ago I lost power at higher rpm's in a pathfinder, that would run fine at low rpm. It turned to be a vacuum leak. A very small rubber vacuum hose loosened with age and leaked where connected to air intake system. IIRC it had to do with the not advancing the timing, do to lack of adequate vacuum.

Similar my 1968 GTO would lose power intermittently on acceleration. Turn out to be timing issue also, from missing rubber ring in a part (new part but from opened box) I'd installed a few months earlier.

 

[APKhaos]

Put a fuel pressure gauge on the injector rail. Its possible that your fuel pump and/or filter are on the way out. High RPM = high fuel flow rate. If the pump can't maintain pressure or the filter can't maintain the flow rate then power will be reduced significantly. Could be other things, but this one is fairly easy to test with a fuel pressure gauge.

 

[LX470 AUS]

Yea I have had vacuum leaks in other cars before, I have a mitivac tester and have been testing all the vacuum lines I can find.
This would make sense though.
I would have thought the crank angle sensor and knock sensors would show an error code if they were shot. Might be possible that they are on their way out and partially functioning, but not enough to throw a code?
I am still curious about the throttle position, if you have the engine off, ingition on, connected to techstream, put your foot to the floor and read the throttle position. It reads 80%. I would have thought it should read 100%.

 

[LX470 AUS]

Just checked all ignition coils with the new one, and replaced the fuel filter, no difference. =(.
Good idea about the fuel pressure gauge. Ill have to get a hold of one and test that.
I hooked up my wifes Corolla to techstream to see if the throttle position was 100% when pedal depressed. It reads 80% as well. So that must be normal.
Ill have to check for exhaust blockage when it cools down.

 

[LX470 AUS]

I think I may have just diagnosed an exhaust restriction.
I tested intake manifold vacuum at idle, it read 19.5 in Hg. I then brought engine RPM up to around 3000, the intake vacuum dropped to around 15 in Hg.
I then removed the O2 sensor plugs from the end of the exhaust manifolds (simulating removing the restriction) and tested the intake manifold vacuum. At idle around 19.5 in Hg, at around 3000 rpm, it read 19.5 in Hg also.
I will take it into an exhaust place tomorrow and see if they can test the exhaust back pressure.