What should the 400 idle at?
Discussion
Hi,
I was having a chat with Mark from Blitz Racong after connecting up my car to his computer. Great bit of kit, but unfortunately I didn't have enough money on me at the time, so I will have to wait to order one from him.
He said my car was idling high and that the stepper motor was set right back at 0% When I got home, as instructed, I clamped the stepper motor pipe and adjusted the screw until it was idling at around 600rpm. Basically as low as it would go without stalling. But when I disconnected the clamp from the pipe the idle rose rapidly and then settled at 1000rpm. This still seems high, and it makes it difficult to drive at slow speeds, in car parks for example.
So, any tips before I try and adjust it again in the morning. Or should I wait to get the computer so I can see what the stepper motor is doing?
Cheers,
Dan
I was having a chat with Mark from Blitz Racong after connecting up my car to his computer. Great bit of kit, but unfortunately I didn't have enough money on me at the time, so I will have to wait to order one from him.
He said my car was idling high and that the stepper motor was set right back at 0% When I got home, as instructed, I clamped the stepper motor pipe and adjusted the screw until it was idling at around 600rpm. Basically as low as it would go without stalling. But when I disconnected the clamp from the pipe the idle rose rapidly and then settled at 1000rpm. This still seems high, and it makes it difficult to drive at slow speeds, in car parks for example.
So, any tips before I try and adjust it again in the morning. Or should I wait to get the computer so I can see what the stepper motor is doing?
Cheers,
Dan
Steve_D said:
Sound to me like the stepper is stuck and needs cleaning.
Steve
I have taken it out and cleaned it, it looked mint. I think the previous owner had cleaned it recently. I'll run it up with it out tomorrow to see if it moves. Steve
Also, Steve, I'm not far from you so I may bring it in for a Heath check and tune up.
Dan, If you switch the ign on then off again can you hear the stepper motor operating, if you can then operate the ignition several times then start it and see what happens, it may even be an air leak from one of the pipes or the plenum. you can check by CAREFULLY spraying easy start or brake cleaner around the plenum and pipework and if the engine idle changes then that is where the leak is. Just don't spray it on or to near the exhaust manifold for obvious reasons, You could even try an ECU reset which may help.
The base idle speed is programmed in the ECU chip, and its set a bit higher in the Mark Adams chips, but not as high as 1000 rpm- that quick test we did on the stepper motor to raise the idle via RoverGauge showed the stepper was not stuck, and the fact that you could get the idle as low as 600 rpm with the stepper feed pipe clamped shows you dont have an air leak. You can get some odd idle issues due to the signal from the "speedo calibration unit" under the dash- this box of poorly designed electronics causes the speed signal that goes to the ECU to go from 0 to about 36 mph in a jump as the car reaches about 3 mph. The ECU now drops out of idle control, and the stepper motor function is changed- now this bit I have not managed to prove exactly what it does- I think it may lift the idle to reduce the engine braking between gears, so if you get an erratic speed signal due to a faulty speedo box at idle it will hold the idle high. It will show up as a speedo reading with RoverGauge, even when the car is still- but I did not see this yesterday, but it can be pretty random as the box of electronics can be prone to electrical noise triggering the speed signal. The Steve Heath ECUmate manual covers the idle control and required sensor conditions in some depth.
http://ecumate.com/docs/Ecumate%20inst.pdf
http://ecumate.com/docs/Ecumate%20inst.pdf
Last night it was idling at around 2000rpm but after a drive it settled down to 1000rpm.
This morning I took it out and it was idling at 1500rpm but would occasionally drop down to 800 or so and then pick up again. It did this repeatedly.
Got home, adjusted the base idle screw to knock back the base idle a bit and it ran fine. Constant 900rpm. Strange.
I've read the coolant temp sender can make a difference so may change that for the sake of £10, but maybe it is this speedo sensor.
This morning I took it out and it was idling at 1500rpm but would occasionally drop down to 800 or so and then pick up again. It did this repeatedly.
Got home, adjusted the base idle screw to knock back the base idle a bit and it ran fine. Constant 900rpm. Strange.
I've read the coolant temp sender can make a difference so may change that for the sake of £10, but maybe it is this speedo sensor.
zed4 said:
Last night it was idling at around 2000rpm but after a drive it settled down to 1000rpm.
This morning I took it out and it was idling at 1500rpm but would occasionally drop down to 800 or so and then pick up again. It did this repeatedly.
Got home, adjusted the base idle screw to knock back the base idle a bit and it ran fine. Constant 900rpm. Strange.
I've read the coolant temp sender can make a difference so may change that for the sake of £10, but maybe it is this speedo sensor.
I was having exactly these problems with mine - I'd love to know where the base idle screw is.....This morning I took it out and it was idling at 1500rpm but would occasionally drop down to 800 or so and then pick up again. It did this repeatedly.
Got home, adjusted the base idle screw to knock back the base idle a bit and it ran fine. Constant 900rpm. Strange.
I've read the coolant temp sender can make a difference so may change that for the sake of £10, but maybe it is this speedo sensor.
QBee said:
I was having exactly these problems with mine - I'd love to know where the base idle screw is.....
On a standard plenum it's on the right hand side of the plenum opening (as you stand at the passenger side of the car) and is recessed down a hole that is *ORIGINALLY* capped off to stop people fecking with it...I *THINK* it's a 3/16ths hex key to adjust it...
Phil
Bassfiend229hp said:
QBee said:
I was having exactly these problems with mine - I'd love to know where the base idle screw is.....
On a standard plenum it's on the right hand side of the plenum opening (as you stand at the passenger side of the car) and is recessed down a hole that is *ORIGINALLY* capped off to stop people fecking with it...I *THINK* it's a 3/16ths hex key to adjust it...
Phil
zed4 said:
....I've read the coolant temp sender can make a difference so may change that for the sake of £10, but maybe it is this speedo sensor.
Whilst the stepper is a common culprit there are other factors.Coolant temp....the ECU thinks the engine is cold so adds fuel.
Throttle position....ECU is not sure the throttle is actually closed.
Speed sensor...ECU thinks the car is still moving. The function holds the idle high during down changes to smooth the change and avoid momentary lock of the rear wheels if the change is a little agressive. This is quite a strong possibility as TVR added a module to simulate this signal when they went away from the LT77 box which gives a good progressive signal reduction down to about 3mph. The TVR box gives 0 or 30mph so is more agin to a switch.
Steve
Just had a re-read of the Steve Heath notes- so in a nutshell the base idle has to be set between 500 and 550 rpm - which is pretty low for a TVR motor, but less so for a Range Rover with a better idle- Anyway the ECU is programmed for smooth idle control between The stepper position 92 and 112- (readable with ECUmate or RoverGauge) and a wrong base idle will make the stepper be outside these limits where the idle control is much courser.
Gassing Station | Chimaera | Top of Page | What's New | My Stuff