Legnum spluttering under low rpm

[Chris]

I've had minimal luck with this Legnum of mine

Anyways last week it was running fine with no issues at all, apart from once where when I was coming to a stop it coughed and spluttered until it stalled.

On the third restating attempt it fired aback into life no issues, I put this down to dirty fuel as it had been sitting around for 6-7 months before I got it together.

Now yesterday the fuel light came on so I proceeded to put about 20 litres of premium in it, after this it hasn't ran properly at all. Backfiring, constant stalling when taking of/slowing down, when it's struggling to run it's throwing clouds of black smoke. Also once it's running it surges too

If I start it and just let it idle it has no issues at all.

No CEL or anything :/

Here's the interesting thing, I plugged a AFM out of a mitsubishi challenger into it and despite the fact it's not perfect when it's running, the surging and low idle issues are gone. Could it be the AFM or could it be due to it coming off a completely different car it's got different values etc and it's just covering up an underplaying problem?

 

[naughtika]

Mitsubishi Challenger would have different values compared to ours (005)

I suggest you replace it with a stock working MAF sensor and go from there...

you could be flooding your combustion chamber with fuel or worse running too lean..

 

[VOLK]

Huge overfuel by the sound of things. Suspect vacuum leak (common), faulty water temp sensor, bad injector, bad FPR (less common) etc. Myriad of causes, including MAF. Sensors can and will randomly start faulting.
Start with the basics: look at the condition of your plugs, post pics if possible. I bet they'll be black with carbon.
They still store codes without lighting a CEL. Check for error codes using link in my sig.

Or, you could just take it to Driven Motorsport and Jonson can figure it out.