Cruise control sloppy

I have recently become the proud owner of a 99 Autobiography 4.6 with a sequential LPG conversion

The cruise seems to work ok generally, but it only seems to keep the vehicle within 2-3 mph either side of the speed i set. This causes the vehicle to gently accelerate and decelerate constantly.

I had a DSE some years ago and I dont remember the cruise deviating at all on that. Is it just a querk of the V8, does anybody elses V8 do this?

I have checked the vacuum pipes and cut them back where they were a little perished but it made no difference.

Any input would be greatly appreciated!

My DSE does exactly the same thing.

The cruise on the petrol is not accurate to +/- .00001 MPH, 2-3 MPH variation is nothing to worry about. Bear in mind you have feedback from the speed sensors (ABS) talking to either the cruise ecu (Petrol) and engine ecu (Diesel).

Let's face it..the Range Rover, Classic, P38 or L322 etc. is about as aerodynamic as a brick and the car will be slowed down by the wind etc. and the cruise will kick in & out. We also have a Vectra with cruise and thats the same, varies and smoothly cuts in & out, maintaing the speed within 5MPH approx. I'm too busy looking out for stupid pr*ts around me than having my eyes glued to the speedo worrying about a 3 MPH difference.
:behindsofa:

Autobiograpy said:

I have recently become the proud owner of a 99 Autobiography 4.6 with a sequential LPG conversion

The cruise seems to work ok generally, but it only seems to keep the vehicle within 2-3 mph either side of the speed i set. This causes the vehicle to gently accelerate and decelerate constantly.

I had a DSE some years ago and I dont remember the cruise deviating at all on that. Is it just a querk of the V8, does anybody elses V8 do this?

I have checked the vacuum pipes and cut them back where they were a little perished but it made no difference.

Any input would be greatly appreciated!

Click to expand...

I reckon as the others have said that it's normal. The Rangie is very heavy and un aerodynamic, any small incline/descent, change in wind speed etc will affect the amount of throttle neaded. The response of the cruise ecu normally lags a little to smooth things out, it also helps economy

mine is the same 4L petrol tried it only the other day maintaing speed but as you described pretty much!it works be grateful that what i say!

Thanks for all the responses, yeah I see what you are all saying! I used to have an Audi A6 which was pretty much on the nose with the cruise control but was a lot lighter I guess and didn't have the aero dynamics of a brick! Was concerned that the vroom vroom nature of the cruise action may have an adverse affect on the fuel consumption. although saying that, I got 280m to 73 Ltrs of LPG on a long run at 65 mph this week, very very happy with that!

Cruise control! you posh lazy get lol.
I just use my right foot. Gives it something to do