range rover 4.0 flat spot advise ...( p38)

[powernut]

hi all .ive what im hoping is a small problem with a slight boggy flat spot in rpms when i rev the engine.it starts idiols great .
also if i rev it slowly it revs fine .but if i blip the throttle pedal underload at low rpm ( 1500/2000rpm it bogs out for a second(also i can hear a slight backfire sputter in the intake chamber.then revs fine threw the rest of rpm range.i can say i didnt notice this fault before i changed engine ( not a bad job tbh .compaired to those td5 engines )
ps ill recheck sparkplugs first .as i never removed them as they looked new .any ideas .advise .just reply .cheers

[maximotorsport]

Sounds like a Worn camshaft

[powernut]

Sounds like a Worn camshaft

really .what i slight flat spot at low rpm ..theres no rattles etc with engine?

[SimpleSimon]

Carry out a fuel pressure check

[powernut]

Carry out a fuel pressure check

how do i do this .ps i have uwed everything from my old engine tbh .

[ChrisJC]

Is this on petrol & LPG?

Chris.

[powernut]

Is this on petrol & LPG?

Chris.

hi chris yes it is .point i. trying to make is old engineran fine apart from the useal overheating issuise .ive then fitted another engine and used everything from the old engine .and doubled checked .for possible pipes.ht leads.conections ..vechicals really nice tbh .ps ive tryed it on petrol and gas makes no differnce issuise is still noricable.starts and idiols dosent seem lumpy .and pulls clean .if this helps clear a few things up .and ive resealed intake plenium .thinking it maybe a air leak.

[powernut]

well i changed fuel pressure reg.maf with no change ill do a vac /pressure check

[Big woof]

Try And change the throttle position sensor off your old engine if that has begun to wear that would also give a flat spot as they are fine contacts and wear away I had the same problem on a 3.9 v8 turned out to be the throttle position sensor fitted a brand new one and the flat spot was removed

[powernut]

Tryed changing that and engine revs its nuts off idiol wont idiol so had to change it bk tbh.
Ive run on just petrol for a week .differnces are..
Cold morning idiol 1500rpm takes a while to drop to approx 800rpm
When warm idiol is very low .struggles to idiol
Did a timing check which looking at the light its pritty stable

[DaveEFI]

Tryed changing that and engine revs its nuts off idiol wont idiol so had to change it bk tbh.
Ive run on just petrol for a week .differnces are..
Cold morning idiol 1500rpm takes a while to drop to approx 800rpm
When warm idiol is very low .struggles to idiol
Did a timing check which looking at the light its pritty stable

The TPS thing needs investigating as it sounds like it is physically sticking if the idle speed changes. All the TPS really does is sense a quick movement of the throttle and enrich the mixture - a bit like an accelerator pump. But in any case if changing it, the output voltage needs to be set correctly.

[powernut]

Tryed changing that and engine revs its nuts off idiol wont idiol so had to change it bk tbh.
Ive run on just petrol for a week .differnces are..
Cold morning idiol 1500rpm takes a while to drop to approx 800rpm
When warm idiol is very low .struggles to idiol
Did a timing check which looking at the light its pritty stable