Just got a call from my dad who is driving my car at the moment.

He just went to start the car to go for a drive and it is running like a pig. Wont start every time and when it does its backfiring and missing and wont idle at all. When he revs it, LOTS of black smoke is coming out the exhaust.

I replaced the battery on Saturday as it was dead and it ran really well all day. He hasnt driven it since.

I cant think of what it could be? I installed a Kompact BOV and Typhoon IC about 2 months ago and thought it might be a hose that's come off and leaking boost, but Dad says all looks ok.

You can see my other mods from my signature. (the Cat and the EDIT havent been put on yet)

Anyone had this problem before, or know possibly what it could be.

I wont be able to get out till the weekend to have a look at it, but if its something simple Dad might be able to fix it himself.

Black smoke is too much fuel going in. What about a re-flash?

Reflash shouldn't be an issue:

the Cat and the EDIT havent been put on yet

Had the PCM re-flashed last service, but that was ages ago and its been running fine. At first the unichip didnt like it but it got better with time.

I've got an EDIT waiting to be put on in the next few weeks, so hopefully if I cant fix it myself any time soon the Tune or tuner will fix it.

If something was faulty my best guess is O2 sensor... if this is reading wrong it will try and dump more fuel in to compensate for what it "thinks" is a lean running engine. Alternatively the unichip might be throwing it all out of whack.

Other things to check are injectors - are they squirting correctly or leaking into the chamber? ummm would busted valve springs cause these symptoms?

Another option is the Unichip.

Maybe it's not "bending" the signal correctly right now and the ECU is supplying too much fuel via the bigger injectors.

Same as when you have the ECU flashed by FoMoCo. You should always consider a touch up on a Unichip afterwards, as the base settings it is "bending" may have changed.

Get rid of the unichip. Problem solved.

Another option is the Unichip.

Maybe it's not "bending" the signal correctly right now and the ECU is supplying too much fuel via the bigger injectors.

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Get rid of the unichip.  Problem solved.

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If it was the unichip, why would it stop working all of a sudden. It was fine on the weekend, today not fine.

Sounds to me more like a hose has come off and its leaking boost, the car cant process the fuel and its running rough.

Yeh I dont think its the unichip... it would have done this right from when u got it back.

From my experience with my own car, when the valve springs dont play the game the car runs like for a short time and there is black smoke under load. If a valve spring fails altogether it will not get better and might cause a problem with the valve being struck by the piston. When mine goes normal operation comes back within a few seconds...

If a hose has come off it could cause rough idle and poor running. Have a good look at all the vaccuum/boost lines etc.

Another thing to consider is, is the unichip doing the job at all? If it isnt changing the signals, the stock ecu will be putting out its own signals and with bigger injectors this would mean WAY too much fuel is going in.

If it's a plug-in type uni-chip why not take it out of the equation?