Missfire only while accelerating on highway when warm

[jas98]

Ok. So have had this for a while (bout 10 000ks now) and doing my head in. Got a ba xr6t stock tune etc

 

When engine gets warm like almost half way on temp guage...when cruiseing on highway at say 70kph to 100kph and gentleing accelerate  the car surges while gaining speed ..kind of sounds like a missfire brrr brrr but revs dont change it still revs up fin when gaining speed. However if I give it heaps (like overtaking etc) it does surge for a couple seconds but then comes good and revs right up like nothings wrong.

 

Went on a 2500k round trip other day...went fine besides this issue. 

 

So far I have replaced:

 

Fuel pump

Fuel reg

Boost solinoid

TPS

Throttle body

cam sensors and checked wireing

Cam actuator soinoids

Oil temp sensor

Oil pressure senor

O2 sensor

Knock sensor

2 lots of coils...current ones are brand new genuine

Spark plugs

 

Also gearbox fluid lines have been by passed from radiator so no chance of coolant mixing

 

Checked for boost leaks and also vacume leaks and could not find any. Idles perfect aswell

 

Each time I replaced something the issue seemed to have stopped for a couple days then comes back. (Could just be me)

 

I have not replaced crank sensor...map swnsor..or injectors ...but surely if it was injectors would do it all time??

 

Can a bad crank sensor only show when warm as a missfire at low rpm?

 

Theres also no codes logged.

[Culbert]

Hi mate. Im currently having this problemwith my f6. Any info you have would be muchly appreciated. 

 

Thanks 

[MBAF]

Does the car have any mods @jas98 is it surging or is it misfiring? Under heavy load? Up hills in 4th or 5th at slow speed heavy load? 

[4321]

Generaly with a ignition problem it will show up under load, as you accelerate you have more air/fuel between the spark plug gap, which makes it harder for the spark to jump (& fire that cyl) Usually caused by a lack of spark. You either increase the spark (new or better coils, voltage booster etc..) or decrease the distance the spark has to jump (close the plug gap- usually 0.7).spark problems with drivability  are normally felt low (engine) speed/ high load . If your thinking crank angle sensor, if you can watch the tacho when the problem occurs, it reads of the sensor so if it acts crazy that will give you a indication of whats going on