Loss of acceleration briefly at 3000 revs

[The Jiffle King]

My chim seems to lose a bit of acceleration at 3000 revs (I suppose it kind of pauses), but at about 3500, really kicks in. Any ideas about what could be causing this?

The reason I ask is that I have booked it in for a service soon and want to go with a little knowledge.

[david beer]

My Griff holds back a little but flies when 3500, thats when the ecu ignores the lambdas i believe.

[soddy]

If it is just a small loss in actual acceleration it is probably just a 'flat spot' in the fuel map .. bear in mind however that the lack of variable cam timing does cause 'neutral' points in the power curve and in some cases even dips. Are you running the vacuum advance on the dizzy? If so try taking it off. It tends to give a smother progression of ignition advance without the vacuum.(make sure you check the timing though .. about 28 at 4000 rpm).

[Mr Freefall]

Mine does this also 5gear 3000rmp one second flatspot then were off, I wondered what this was also.

No such effect in 4th just in 5th.

[mrt1040]

Mine does this as well,
I've found an airleak from the plenum which I believe
may be causing the fault. I can't confirm this as i've not had the chance to fix it yet.
I'll keep you informed.

Mark

[Mark Adams]

David Beer is right. If your car is a catalyst car running on a standard chip, then the car is on Lambda control until 3100RPM exactly. It is quite common to feel a flat spot here if the map does not perfectly suit the engine.

If your catalyst car is a 4.0 or 4.3 Litre then it is most likely to go rich here. If it is a 5.0 Litre then it is probably going lean.

[the jiffle king]

I do feel re-assured, I think I'll mention it at the service and see what they say. It's quite difficult to define a flat spot, so I'' post when I find out

T-J-K

[jacksdad]

I have exactly the same thing on a 4.0 HC and when I asked on the last service I was given TVR response No 1.


"Don't worry Sir, they all do that !"