Drop in Revs and Power at 2600RPM up to 2900RPM - Toyota FJ Cruiser Forum
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post #1 of 14 (permalink) Old 04-29-2018, 09:57 AM Thread Starter
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Unhappy Drop in Revs and Power at 2600RPM up to 2900RPM

Hi guys.
I have a 2011 FJ cruiser Auto.

If the Engine is under load (so towing something), and I get to 2600 RPM, the power backs off and the Revs fall to 2500 RPM, it then recovers and drops again at 2700 RPM back to 2600RPM, then recovers again and goes up to 2800RPM and drops off again to 2700 RPM, until it gets to 3000RPM and it then performs fine after that. (See attached Image (Revs.jpg) from ODB2 connector that shows the "dips")

The Fuel pump has been blamed, but it performs perfectly when accelerating normally, or when doing full throttle acceleration.
0 - 100 KM/H is passed in 7.5 seconds, Dyno results show 190kw on the engine. FJ has a Free flow.

I bought it with 60,000km on and it already did it back then (3 years ago) and I have put on 100,000km and still doing it. If it was fuel pump I think it would have failed by now.

I suspect (and I cannot proof this) that the previous owner might have had software remapping done on the FJ and this might be causing the issue. He had 33" (or bigger tires) on the FJ, and when I bought it we went back to the Std 265/70/17. (So the Engine Torque is no set incorrectly for the smaller wheels?)

If we Disconnect the MAF sensor, to force a Full fuel mixture, then the power is down a bit, and the engine light comes on (as expected), but then the issue is NOT there any more. So this seams to point towards the fact that fuel mixture is to lean, and this is causing the issue. I have taken the MAF sensor out and cleaned it with Brake Cleaner, it made no difference. Sensor looks really clean even before I cleaned it. Also no ODB2 Error codes are being shown even with a Deep Scan, but I have a "Cheap" OBD2 and App so not sure how much to trust it. It did go to a Service center and they also did not get any Error codes, with their expensive ODB2 reader.

Why it ONLY happens at this Engine RPM's and ONLY when engine under load, I cannot figure out.

Any insights would be greatly appreciated.

I have attached some OBD2 charts, each of the charts is a different measure (Sensor) and each of them was a independent run on the road, hens the Revs are a bit different. The Summary chart shows a few of them cut and paste into a single chart, I added the Red lines to make it easier to see how the Revs drop correlates with the Sensor readings.

Thanks
Michael
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post #2 of 14 (permalink) Old 04-29-2018, 12:03 PM
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

Almost sounds like it's going temporarily into safe "limp" mode. I've never had this problem on any car I've owned but my daughter had an Accord with a bad crankshaft pos sensor that would not let the engine go above 3k rpm. It caused an cel code though. If the previous owner did run some type of "performance" software there still should be a programmer attached at the ecu I would think. I only know of one way to overwrite the FJ ecu and that is a Toyota flash such as for a supercharger but that changes a variety of engine specs not just supplementing for tires. Without a programmer hooked up and feeding false info to the ecu I think once detached the stock ecu parameters return to spec.


I could be wrong though, I'm just brainstorming with you...

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post #3 of 14 (permalink) Old 04-29-2018, 07:31 PM
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

MH -

Two questions:

1. Does the RPM anomaly occur while the engine is under load, but at constant throttle position? (Or are you modulating the throttle position in an attempt to "get past" the RPM dip?)

2. Have you also monitored ignition timing during the anomaly?
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post #4 of 14 (permalink) Old 04-29-2018, 11:19 PM Thread Starter
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

Yeah, no Chip in there.
It is possible to Remap the software, nothing is then connected after the software (Settings) are overwriten, and you drive away, no one would know any better..

I`m trying to get hold of the original owner, and will ask him.

Thanks
Mike
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post #5 of 14 (permalink) Old 04-29-2018, 11:21 PM Thread Starter
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

Hi.

Yes it happens when I hold the throttle in a stable position, I do not add more power. This is VERY important, and I am glad you are asking it, since if I power more, it is at that point it will kick back another gear and then takes off like a rocket...
The bad thing is that it is exactly at 120km/h where this would happen, so cruising speed. if you doing 120km/h you are at 1900/2000 RPM, then you hit a hill and need to apply a bit of power to keep your speed, this is when it will kick back to the previous gear and hit that 2500RPM spot, and start with its issues. So it is Extremely irritating.

I have tested Timing advance, and the Chart, unfortunately not attached (I did not safe it), did not do anything in relation to the Drops in Revs...

Thanks
Michael
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post #6 of 14 (permalink) Old 04-30-2018, 01:02 AM
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

Strange,,, Have you tried a different MAF from another car just to rule that out?
O2 sensor? Do you have a stock exhaust / headers? or does it have an O2 sensor simulator?

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post #7 of 14 (permalink) Old 04-30-2018, 01:25 AM Thread Starter
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

Quote:
amaclach previously said: View Post
Strange,,, Have you tried a different MAF from another car just to rule that out?
O2 sensor? Do you have a stock exhaust / headers? or does it have an O2 sensor simulator?

I am going to try another MAF sensor, someone has one I can test with. Just trying to organise.
I have a Freeflow, from Y-Pipe to tip has been replaced with new 76mm Stainless steel exhaust.
Original O2 sensors still in Manifold that was not replaced.. Not sure about Secondary O2 sensor, need to check, but I understand they have no impact other than CO2 emissions.. and CATS were removed all 4...
Thanks
Michael
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post #8 of 14 (permalink) Old 04-30-2018, 04:12 AM
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

I reckon that's part of your problem. somewhere between the O2 sensors and the MAF.
Good luck and keep us posted!

Have a look on the OBD tool and see if there's any correlation in readings on the O2 sensors?
If the O2 sensors are sending a false rich reading, the engine might be running lean, which might not be ideal.

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post #9 of 14 (permalink) Old 04-30-2018, 04:21 AM Thread Starter
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

Quote:
amaclach previously said: View Post
I reckon that's part of your problem. somewhere between the O2 sensors and the MAF.
Good luck and keep us posted!

Have a look on the OBD tool and see if there's any correlation in readings on the O2 sensors?
If the O2 sensors are sending a false rich reading, the engine might be running lean, which might not be ideal.
It did it before the Freeflow was fitted and the CATS removed.. so it is not related...

I`ll check it anyway, to see what the chart shows.

Michael
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post #10 of 14 (permalink) Old 04-30-2018, 05:31 AM Thread Starter
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Re: Drop in Revs and Power at 2600RPM up to 2900RPM

Quote:
amaclach previously said: View Post
I reckon that's part of your problem. somewhere between the O2 sensors and the MAF.
Good luck and keep us posted!

Have a look on the OBD tool and see if there's any correlation in readings on the O2 sensors?
If the O2 sensors are sending a false rich reading, the engine might be running lean, which might not be ideal.
See attached the O2 Sensor chart... Just tested it now.
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