Diagnosing Fuel/boost cut around 4000rpm

[bean]

My car has been running crappy for a long time, won't rev over 2500rpm etc...

Would any kind/local R enthusiast fancy giving me a hand sorting the problem? I'm quite poor at the moment but can pay in beer.

 

[antilag]

bean cum round mine tomorow if u want and we can swap sum bits over ect if u like

 

[bean]

bean cum round mine tomorow if u want and we can swap sum bits over ect if u like

Thanks, I'll be in touch.

 

[gtirpulsar]

Your MAF is unplugged....

 

[stomski]

yep, sounds like MAF sensor loose, i had same problem, check you have the right silver thin clip thingy on it.

 

[bean]

Thanks guys will check that.

 

[charlie]

sounds like its in limp home mode (not low boost mode) are the rad fans on all the time now too?

apparently some things that cause limp home are

maf sensor circuit
throttle position sensor
coolant sensor

anybody else care to add? im sure i missed some.

 

[antilag]

were gonna swap his maf for mine and try that we sorted out a few other problems with the car today but the fault code reads det sensor and its a violent cut it ent im limp mode either

 

[bean]

Dave and I had a look at it today, found the air leak on the inlet manifold side (boost gauge now reads vacuum at idle) and removed/cleaned a leaky injector.

I'm still getting a kinda violent boost cut around 4000rpm I guess (cos my rev counter ain't working properly, bouncing around randomly), also getting intermittent misfiring when accelerating.

ECU fault code check says DET sensor, 3 short followed by four long flashes.

This is turning into a complicated one... :? :x

 

[bean]

Tried swapping my AFM with a known good one, didn't cure the problem.

Still getting a boost/fuel cut around 4000rpm in every gear, car's limited to a top speed of 75mph! :x

Any other ideas? :roll:

 

[bean]

Topic name changed to something more appropriate...

 

[Fast Guy]

I'm still getting a kinda violent boost cut around 4000rpm I guess (cos my rev counter ain't working properly, bouncing around randomly), also getting intermittent misfiring when accelerating.

ECU fault code check says DET sensor, 3 short followed by four long flashes.

It sounds like you maybe be detting then. Does it only do it when driving or if you're stationary and rev the car?
It might be worth sorting the rev counter out as you never know, it could be related to the main problem.


Check your ignition timing is ok.
Check your injectors/dropping resistor are working.
Check the ignition amp is ok.
Check your fuel pump isn't on the way out.

Failing that, try and get it to a garage that can check things with the car running. (Crypton tuning place/rolling road/Nissan consult) but make sure they know it's a turbo and is possibly detting.

 

[Keira]

(cos my rev counter ain't working properly, bouncing around randomly),

Do the revs fluctuate with it ?

A mates cossie was doing all sorts of strange things, rev counter bouncing around but revs staying constant, fog lights flashing on with the brakes, engine didn't want to know under load etc, etc.

He spent £'s replacing bits and pieces and it turned out to be bad earths, spent a day cleaning them up and its running aok now, would've cost absolutely f*ck all if he'd done them first :roll:

 

[bean]

Thanks guys,

I've taken the car off the road now so I can work out what's up with it :shock:

I get the cut when driving and if I blip the throttle whilst stationery, kind of momentary cut before it picks up again.

I've checked the timing and it's fine, I think the injectors are ok as they're firing and getting power ok.

I've not checked the fuel pump, dropping resistor or ignition amp, where is the ignition amp? :?

The rev counter did go haywire around the same time, flickers sometimes then it's dead other, seems a coincidence and bad earth seems feasible. :roll:

Which main earths do I need too check?

I'll post my progress later in the week, in the meantime I'll be getting to work by train.

 

[sypher]

i think the 2 main engine earths are the ones on the plenum you could check these and there is one on the gear box that is a spade terminal. then put a jump lead between engine and neg pole of battery... check for air leaks at vac' pipes and big intake pipe between air flow meter and turbo, this could be an un-metered air leak..

 

[bean]

i think the 2 main engine earths are the ones on the plenum you could check these and there is one on the gear box that is a spade terminal. then put a jump lead between engine and neg pole of battery... check for air leaks at vac' pipes and big intake pipe between air flow meter and turbo, this could be an un-metered air leak..

I did tug at the pipe that goes from the boost solonoid to the big intake pipe, might have a leak there? Didn't think it'd cause the weird cutting out though :shock:

One more thing to check eh?

 

[sypher]

sorry if i wasn't clear i meant the pipe DIRECTLY onto the turbo intake or a split in this pipe.. to my knolledge so far an unw-illingness to rev could be incorrect cam/crank timing or airflow problem this includes the pipes blocked filter or a miss reading air flow meter. i had this on an alfa 155

so is it just an unwilling to rev engine or missfire

 

[Fast Guy]

Check all the wires to the coil for breaks too. I had a mate years ago and his engine would do something similar, when he revved it, it would go to a point then die. Eventually it turned out to be a broken wire to the coil that was normally continuous, but as the engine moved on the mounts when revving, it broke the wire and cut the ignition system, hence the engine died, the engine moved back on it's mounts and jumped into life again.

Failing that, a crypton tune place should be able to pinpoint something if it does it when you're stationary and rev it.

 

[bean]

I'll check the main intake pipe again for leaks.

I did notice that there's a scotchlock connector on one of the power leads to the coil, I'll remove that and check the wire isn't broken.

 

[Fast Guy]

Check/change your coolant temp sensor. When my car is cold it cuts at 4000rpm to stop you booting it. Maybe your sensor is goosed and the ecu thinks the engine is cold and it's cutting it.