Hey everyone

Ive got a RX8 03 MT 5 Speed 4 port , KN Filter and Gutted cat with anti fouler O2 sensors

Issue is hesitation after 4500rpm (ish) right before you get the rpm kick and engine sucks more air , it does not last long its there for maybe 1 second but it is noticable. Like a small hiccup and then it goes but its a really big disadvantage and makes the car feel a bit low on power afterall it is a fu*king sports car

Ive been premixing 150ml to 200ml per tank but got told that 2t oil would clog the injectors.

Car has 45.000km , coils are new , plugs were changed not so long ago , leads are ok , new maf sensor , oil changed with filter every 2000km. No codes on diagnostic

Starts up quick when its cold , but when its hot it takes a bit longer to start , if i shut it off after one start and try again it starts quick as when its cold. Does not have the standard '' hot start issue'' I suspected it could be the fuel pump because once pressure is built up it starts normally. I have ordered a 340LPH fuel pump with sock from ebay
SSV valve moves nice and freely

So which of these things could it be?

- Fouled plugs due to premix?
- Fuel pump?
- Ignition leads?
- Injectors? Would ultrasonic cleaning improve them?

 

My guess is that it's running a little rich and bogging slightly as the SSV opens .
Possibly could be as a result of the o2 sensors you have fitted .... not actually sure what an "anti fouler" sensor is supposed to do but it sounds kinda like BS to me .

 

I have never had any CEL because of O2 sensors and i checked the Cat its empty inside
Got told it had some kind of defouler installed on O2 sensors to make the ECU think all is well.

These O2 sensors have been installed before i got it , i bought the car in 2007 and ran fine when low mielage , after premixing this kind of sh*t started to happen

Never had a CEL which had anything to do with emissions

 

do you have anyway of logging or reading the air/fuel ratio ?

 

Sorry for the late reply was travelling.

I do not have anything to measure AFR ratio , no aftermarket gauge but can get a ELM Bluetooth OBDII diagnostic thingy if that does the job.

The reason im pretty sure fuel pump is faulty is because when i start the car first time in the morning it takes a little time to start up , temps here are over 30C so cold start procedure doesnt engage yet. But right after it comes up to temp if i shut it off and start it back again it starts quick as it was a brand new car. And it is actually more responsive when driving a few 100 meters from my house when i assume the fuel pump is cold.

Going to change the pump tomorrow with a Denso unit , i bought a 355LPH pump but read here on the forums that it will blow off a valve into the fuel tank , that sucks and i presume i dont even need a more powerful fuel pump

 

It isn't the fuel pump ...that I can assure you .
And fitting that 355 pump will cause more problems than it solves .

Start by reading what your air fuel ratios are when this hesitation occurs .
Is the front 02 sensor stock Mazda one ? If not ..... that is the first thing I would replace.

 

First sensor is stock Mazda , ive got it hooked up to diagnostics and no codes show up other than Airbag.

So long startup time could have something to do with the O2 sensor? I have noticed the car shutting off randomly 2 times after a long trip with highway driving

Sounds good reading AFR when hesitation occurs because that is absolutely not hard to replicate.

Its got the stock Arram pump which i have read is ****

 

Well just installed a complete new housing with new pump and the car pulls great all the way to redline

When old housing was opened the pipe from the bottom to fuel pump was actually broken hence not giving enough pressure. Only solution was to get a new housing since this could not be repaired.

Anyone suffering from same issue please check your fuel pump , sock , housing. Change fuel pump if possible with a denso unit

 

Damn ...sorry to steer you the wrong way there man.