Discussion
Hi all.
I got very close to the emission limit during the last MOT and thought I'd try the ECU reset as a first step before getting them checked again.
I've done this a few times before and it seems to clear the problem but then they creep back up again. It also seems to cure the intermittent misfire when pootling along at low throttle.
The only problem this time is that the engine dies when the TPS is disconnected, it won't start without it either.
As the old one has been on since before I got the car in 2008, I was thinking of getting a new one anyway here:
https://www.ebay.co.uk/itm/MG-MGZR-105-120-Acceler...
But before going ahead could there be another problem as to why it won't start/idle without it?
Cheers,
Steve
I got very close to the emission limit during the last MOT and thought I'd try the ECU reset as a first step before getting them checked again.
I've done this a few times before and it seems to clear the problem but then they creep back up again. It also seems to cure the intermittent misfire when pootling along at low throttle.
The only problem this time is that the engine dies when the TPS is disconnected, it won't start without it either.
As the old one has been on since before I got the car in 2008, I was thinking of getting a new one anyway here:
https://www.ebay.co.uk/itm/MG-MGZR-105-120-Acceler...
But before going ahead could there be another problem as to why it won't start/idle without it?
Cheers,
Steve
SteveOS3 said:
Hi,
there's only one way for the throttle spindle to engage with the TPS and the TPS is in a fixed position so I guess the answer is there's no adjustment.
Steve
Yes but i can imagine some are slightly out of tolerance on the casing ive have known them to be slotted out and adjusted to attain a correct reading at base idle.there's only one way for the throttle spindle to engage with the TPS and the TPS is in a fixed position so I guess the answer is there's no adjustment.
Steve
If it's a 2.9, with EEC-IV engine management, there's no base idle adjustment. Idle speed is managed directly by the ECU; it's part of a feedback loop, so there's no calibration of the TPS necessary.
The critical thing is that the throttle must be able to close completely, so there's no air passing through the butterflies at idle. There's a 'closed' stop on the butterfly mechanism, but this needs to be set so the butterflies don't 'snag' in the throttle bores in the closed position. It mustn't hold the throttle open, even a tiny bit. That way, the ECU can get on with its job of maintaining idle speed.
Critical factors are that the TPS has a perfectly linear action (no breaks or dead spots) and that the mechanical action from the pedal to the butterflies is smooth throughout (no snags or jerks), and the mechanism mustn't hold the throttle open at idle.
And, of course, the ISCV must operate correctly and smoothly.
The critical thing is that the throttle must be able to close completely, so there's no air passing through the butterflies at idle. There's a 'closed' stop on the butterfly mechanism, but this needs to be set so the butterflies don't 'snag' in the throttle bores in the closed position. It mustn't hold the throttle open, even a tiny bit. That way, the ECU can get on with its job of maintaining idle speed.
Critical factors are that the TPS has a perfectly linear action (no breaks or dead spots) and that the mechanical action from the pedal to the butterflies is smooth throughout (no snags or jerks), and the mechanism mustn't hold the throttle open at idle.
And, of course, the ISCV must operate correctly and smoothly.
Edited by mentall on Tuesday 9th June 17:18
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