range rover 4.6 flat spot

stagcar · Post by **stagcar** » Wed Sep 28, 2011 1:34 pm

Hi chaps,

The manta v8 build is still in progress so i am sure i will be hounding you all about this very soon

At the moment i am running around in a 97 range rover HSE 4.6

running on LPG its fine but when it on petrol it seems to hold back at about 3000 rpm it feels like a misfire. up until that it pulls well and seems to be more powerfull than on the lpg

any ideas? i would normaly have done plugs and leads but seeing as its fine on lpg i dont recon that can be the problem.

any help would be apriciated

Many thanks derek

ChrisJC · Post by **ChrisJC** » Thu Sep 29, 2011 7:04 am

Is it a fuel injection LPG system that piggybacks on the GEMS engine management? So it's reusing the GEMS map?

Chris.

Eliot · Post by **Eliot** » Thu Sep 29, 2011 8:37 am

How much fuel is in the tank? - Mine cavitates when its down to the last line, well before the light comes on.
Mine was pretty flat in the midrange as was my previos p38 as well. I've megasquirted mine now - no more flat spot or air flow meter for that matter.

stagcar · Post by **stagcar** » Thu Sep 29, 2011 9:28 am

Thanks for the replys chaps

TBH i havent a clue how the lpg works it looks to me like its got its own ecu and i think its got its own lamda also.

as for the fuel at the moment its got about half a tank of fresh juice.

I have found that if you can get it past the 3000 rpm it seems to get better at about 3800 but still not good

looking on the net i am thinking airflow meter? has any one had these die before?

like i say this is normaly not a big problem becuse i use it on LPG most of the time its just a pain when it runs out and switches back to petrol specialy when your wipping it up the motorway

Thanks again
Derek

Eliot · Post by **Eliot** » Thu Sep 29, 2011 10:13 am

Try removing the AFM and cleaning it with isopropol or contact cleaner. Not a 100% fix but it should improve things if it is flaky(dirty).

ChrisJC · Post by **ChrisJC** » Thu Sep 29, 2011 11:53 am

You could try getting any faults read out of the ECU.

Chris.

Eliot · Post by **Eliot** » Thu Sep 29, 2011 1:28 pm

Unless its really broken, it probably wont show anything.

I chased my arse on my hesitating P38 - turned out to be the fuel cavitating in the tank. Although it was the diagnostics that helped me find it, because i could turn the fuel pump on manually and i happened to hear it. I was actually trying to test the fuel pressure at the time - so i was close!