Rpm problem

[Alan8360]

Hi there hoping someone can help me I have an 03 corolla t sport when I hit 7200rpm the power cuts in and out violently like some one is flicking a switch has any one had this problem before and know what's causing it many thanks Alan. 

 

[Corolla2004]

Could this help .... 

 

[Alan8360]

Car was definitely up to temp had been driven for at least 5 miles before I noticed the problem when I went to over take. 

[Tomo86]

I would try clean the lift screen and see if it would make a difference.

[Alan8360]

Hi there recently posted asking for advise on what I thort was a variable valve problem because car would only rev to around 7k since the it's got progressively worse and now only revs to 5k then cuts out like turning ignition off and on any help as to what is wrong would be really appreciated as I'm getting desporate now and cnt do without my car. 

[FROSTYBALLS]

Topics merged.

[KennyKen1988]

What about stationary revving is the cutting out issue also happening in this instance?

Any check engine lights coming up?

[Alan8360]

Seems fine stationary only does it under load have the engine management light come on twice now code read cat bellow efficiency bank 1 but have fitted a new cat back in Jan and havnt done many miles since. 

[Alan8360]

Update after many tests and inspections car won't rev over about 5200rpm driving or stationary wen it gets there it misses and pops out the exhaust also more often than not get a strong smell of fuel. Plugs indicate its running lean or hot only fault that has come up twice is P0420 have monitored o2 sensors and graphs are matching ii guess implying cat in shot but is only 6 months old and only done max couple hundred miles. Has anyone got any ideas wat is wrong? 

 

[KennyKen1988]

P0420 is a very vague code and can be a nightmare to suss out. When it states bank1 it has to be as it's a four cylinder there is no second bank (like a V6/8 etc...)

I can only go off experience from my dad's Zafira A 1.6 Club. One of the o2 sensors failed causing a run rich scenario which superheated the CAT and collapsed the monolith. We had to replace the o2 sensor of course along with the CAT and all was well again, running wise emissions is good every year. The thing is the P0420 code returned no matter what, no exhaust leaks, new CAT, new exhaust system, new sensors. Found out with Vauxhalls this code can just keep coming back when you change the CAT. We ended up gapping the post CAT o2 sensor to keep the engine management light off.

If you are confident all is well with the exhaust system just get the secondary o2 sensor gapped and it should get rid of the light. When you mention "cat back" do you mean a catalytic converter back in Jan or a "cat back" as in a cat back performace exhaust system?

I'm wondering if the P0420 code is restricting the ECU to allow you to push the engine up into the higher RPM.

If you can do any live data recordings for the o2 sensors that may help you, did you replace any parts of the exhaust yourself? Of course listen out for any exhaust manifold leaks also?

[doc_14]

Some four cylinders have 2 banks, for example, engine 1AZ-FSE.

Is the fuel filter and the pump ok? Can be a lack of fuel pressure in high rpm. Also check the MAF, since going that high RPM sometimes use MAF instead of oxygen sensors (Open loop)

[Alan8360]

I have changed lift bolts and cleaned lift screen also have reinstalled the old exhaust even tho it used to throw the P0420 regularly it used to run fine and still the car won't rev past 5k some times it will go to 5500rpm I am suspicious of possible exhaust manifold leak but heads of bolts holding heatshield are rotten off so cnt remove to inspect. Lack of fuel has crossed my mind but don't know how to prove it so I'm thinking maybe maf sensor or another sensor somewhere is failing really don't know what to try next have also noticed engine as a few ruff running spots on the way up to 5k I'm worried at this rate its just going to die. 

 

[doc_14]

Try disconnecting the MAF sensor and see if it makes any difference. Without the MAF, the car should use the standard maps stored in the memory but also can cause it to go into limp mode. Anyway, it is a simple test.

[Alan8360]

Yeah have tryed that goes into limp mode and only revs to 3k then. 

[Alan8360]

New maf sensor fitted and still the same is fuel pump/ fuel filter easy to access? 

[doc_14]

Have you tried to disconnect the oxygen sensors to see if anything changes? The fuel pump is usually under the back seat but is a bit difficult to take off

[Alan8360]

Haven't tried disconnecting them do you think it's worth a try am up for trying anythink if it means I find the source of the problem. Am I right in thinking that wat limits engine revs wen its cold is oil temp if so where is the sensor? I thinking with every think I've tryed it has to be either lack of fuel or electrical limiting the rpm. 

[doc_14]

Whell... the computer will then use the mappings but eventually can go into limp mode. But i'm pointing to the lack of fuel. Try change the fuel filter. When was the last time that you have changed? Some filters are inside the pump and those unfortunately are irreplaceable

[Alan8360]

Update my problem is temperature related engine running normal temps gauge reads normal but ecu thinks engine is 93 degrees c does anyone know what and where is the temperature sensor thanks

[Tomo86]

Just below the oil control module

(Where the lift screen is)

Has 2 wires connected to it it's the coolant temp sensor

[Alan8360]

Thanks for the quick reply is this the only temp sensor? 

[Tomo86]

18 hours ago, Alan8360 said:

Update my problem is temperature related engine running normal temps gauge reads normal but ecu thinks engine is 93 degrees c does anyone know what and where is the temperature 

 

Not 100% sure.i had to run a extra sensor for pfc.i paid about 15 for one.sorry I couldn't be more help

[Alan8360]

Update new temp sensor installed and still no different ecu still thinks engine is 90+ has now thrown code for coil number 4 cleared it and hasn't come back am at compleat lose of ideas no cnt afford to keep spending money on parts that don't fix it surely someone knows somethink car revs to 7k cold but no valve lift as soon as up to temp only revs to 5k. 

[KennyKen1988]

Perhaps leave the Battery disconnected and start over the next day. Have you inspected the coils? Only going from my car the individual coils seem to be very reliable, perhaps check the spark plugs also. Review anything you can if it's not going to cost you anything. When you describe the power as cutting out violently in your original post is there anything noticeable in the interior, does the dash cluster flicker?

 

[Alan8360]

Have tryed plugs they do seem to indicate it's running lean have swapped the coils round hasnt thrown the code again not convinced they are bad am going to try disconnecting the Battery today as a last resort. When it first stated playing up didn't notice anythink abnormal with the dash was like turning the key on and off and was violent because was on valve lift. I'm convinced it's electrical but no idea wats causing it and why the ecu thinks the engine is so hot.