ECU stupid or clever ?

[WokingWedger]

A few weeks ago I fitted a stepper hose Restrictor, which has been working a treat, much easier to drive and no revs hanging. I used the SC kit and had to open the hole up a bit.

Just today the revs were hanging high again. How ? Can the ecu learn to open the stepper motor more after a while ?

After approx 20 mins of urban driving the car tried to cut out when stationary for a few mins ( had to hold the revs up) but then settled back to high revs scenario.

I will clean the stepper when things have cooled down, but it was done not to long ago.

Thoughts anyone ?

[Englishman]

Why did you fit a stepper hose restrictor (actually never heard of this before) as you shouldn't need one and suggests another problem.

[Steve_D]

Thinking a restriction was required rather implies to me that the base idle had not been set correctly.

Steve

[blitzracing]

The stepper restrictor is a really bad idea- something else is wrong. This could be base idle as already suggested, air leak in the plenum, wrong throttle pot setting, wrong speed input, wrong temp reading. The ECU will control the idle quite nicely if everything is in order.

[WokingWedger]

blitzracing said:

The stepper restrictor is a really bad idea- something else is wrong. This could be base idle as already suggested, air leak in the plenum, wrong throttle pot setting, wrong speed input, wrong temp reading. The ECU will control the idle quite nicely if everything is in order.

Well you have changed your tune ! (Your post 17th Jan 2008). Excuse the pun (tune)

With out restrictor , It runs as per everybody else's (holds 1200 rpm for a few secs) and I hate it !

[Belle427]

I cant comment on the ecu part but rightly or wrongly i put a small restriction in the hose too, i didnt like the behaviour of the revs between changes etc. I prefer the way the car behaves now, the idle didnt increase on mine and that was put in a while ago.

Edited by Belle427 on Sunday 26th June 19:18

[peaktorque]

WokingWedger said:

Well you have changed your tune ! (Your post 17th Jan 2008). Excuse the pun (tune)

With out restrictor , It runs as per everybody else's (holds 1200 rpm for a few secs) and I hate it !

Mine doesn't.

[blitzracing]

WokingWedger said:

blitzracing said:

The stepper restrictor is a really bad idea- something else is wrong. This could be base idle as already suggested, air leak in the plenum, wrong throttle pot setting, wrong speed input, wrong temp reading. The ECU will control the idle quite nicely if everything is in order.

Well you have changed your tune ! (Your post 17th Jan 2008). Excuse the pun (tune)

With out restrictor , It runs as per everybody else's (holds 1200 rpm for a few secs) and I hate it !

Absolutely- given the correct tools you can see whats the ECU is trying to do, and how it does it- Im no longer in the dark ages!

[WokingWedger]

If I could just find my Rovergauge cable and remember how to use it I could check a few things, but Isn't it generally agreed that the ECU holds the revs 'by design' hence its fitted with a road speed input.

[Pupp]

The hanging idle glitch was *the* determining factor for me in deciding to junk the Lucas ECU and go aftermarket.... I chased the problem around for literally months and do recall reading more than once from those that know the system initately that there was accepted to be an issue with the ECU code that caused this in certain conditions even with all sensors inputting correctly. I never did resolve it (the restrictor trick did provide a mostly effective workaround) and it did spoil enjoyment of the car for quite a while.

Suspect those that have not experienced it just do not drive enough miles to encounter the triggering conditions

[WokingWedger]

Pupp said:

I never did resolve it (the restrictor trick did provide a mostly effective workaround) and it did spoil enjoyment of the car for quite a while.

Suspect those that have not experienced it just do not drive enough miles to encounter the triggering conditions

Did the restrictor work permanently for you or was it only temporary or a stop gap until going aftermarket ECU anyway.

[Englishman]

Pupp said:

The hanging idle glitch was *the* determining factor for me in deciding to junk the Lucas ECU and go aftermarket.... I chased the problem around for literally months and do recall reading more than once from those that know the system initately that there was accepted to be an issue with the ECU code that caused this in certain conditions even with all sensors inputting correctly. I never did resolve it (the restrictor trick did provide a mostly effective workaround) and it did spoil enjoyment of the car for quite a while.

Suspect those that have not experienced it just do not drive enough miles to encounter the triggering conditions

Would you expect to experience it in over 200,000 miles/30 years of driving in RV8 based TVR's? Had stepper motor sticking issues a few times but never had a high idle issue that couldn't be resolved.

[Pupp]

Englishman said:

Would you expect to experience it in over 200,000 miles/30 years of driving in RV8 based TVR's? Had stepper motor sticking issues a few times but never had a high idle issue that couldn't be resolved.

Well, please do share the resolutions arrived at; I'm sure the OP and others will be grateful for the pointers.

[Pupp]

WokingWedger said:

Did the restrictor work permanently for you or was it only temporary or a stop gap until going aftermarket ECU anyway.

I ran with restrictors of various sizes for a long time until going aftermarket; it did compromise warm up behaviour but I preferred that to random holding onto revs at junctions etc... on mine, the stepper was not 'sticking' due to carbon fouling or wear it was being held in an open position by the ECU. This all pre-dated Rovergauge etc so I never had the ability to interrogate the ECU to see why it might be doing it but did pretty systematically work through senders and wiring etc without ever identifying a component fault. Hope someone does post up a certain fix; it eluded me

[WokingWedger]

Englishman said:

Pupp said:

The hanging idle glitch was *the* determining factor for me in deciding to junk the Lucas ECU and go aftermarket.... I chased the problem around for literally months and do recall reading more than once from those that know the system initately that there was accepted to be an issue with the ECU code that caused this in certain conditions even with all sensors inputting correctly. I never did resolve it (the restrictor trick did provide a mostly effective workaround) and it did spoil enjoyment of the car for quite a while.

Suspect those that have not experienced it just do not drive enough miles to encounter the triggering conditions

Would you expect to experience it in over 200,000 miles/30 years of driving in RV8 based TVR's? Had stepper motor sticking issues a few times but never had a high idle issue that couldn't be resolved.

You NEVER came to a stop at traffic lights and felt the revs are to high for a few secs? NEVER?

Or when slowing down in gear felt the car pulling instead of slowing ,or noticed the revs dont drop enough when changing gear, none of this ?

If you have never experienced it, you are very lucky, or if you have and have 'fixed it, then yes seriously, any pointers as to what to check would be gratefully received.

[Englishman]

WokingWedger said:

You NEVER came to a stop at traffic lights and felt the revs are to high for a few secs? NEVER?

Or when slowing down in gear felt the car pulling instead of slowing ,or noticed the revs dont drop enough when changing gear, none of this ?

If you have never experienced it, you are very lucky, or if you have and have 'fixed it, then yes seriously, any pointers as to what to check would be gratefully received.

If you read my post I said I'd never had a high idle issue that couldn't be resolved, not that I'd never experienced them. In terms of fixes, I can’t recall a time when cleaning the stepper motor and housing thoroughly didn’t fix it though. I also get my cars serviced once a year by a top TVR garage that knows what they are doing, so I expect that prevents other issues.

[blitzracing]

Steve Heath covered the idle control in depth in the ECUmate manual, and explains why you get the wrong step down rate if one of the settings is wrong. read page 37 onwards:

http://ecumate.com/docs/Ecumate%20inst.pdf

[WokingWedger]

blitzracing said:

Steve Heath covered the idle control in depth in the ECUmate manual, and explains why you get the wrong step down rate if one of the settings is wrong. read page 37 onwards:

http://ecumate.com/docs/Ecumate%20inst.pdf

Yes its a good write up, thanks.

I note he also says 'When the car stops, the road speed signal will
also stop and about 2-3 seconds later the ECU will enter idle mode
and start to reduce the engine revs.'

This is what is annoying. This delay, and when crawling at 5 mph having high revs.

He also states 'When the throttle is released, the ECU will not attempt
to bring down the revs because the car is moving.
This means that the revs are kept higher during a gear change to help
prevent rear wheel lock up and that the ECU will only go down to
the low idle speed if the throttle is below the idle threshold and there
is no road speed signal.'

I don't want the revs held high when changing gear ! If I did I wouldn't bother taking my foot off the throttle.

Both the above are by design when everything is working as it should.

Its far from ideal !


I cleaned my stepper (plunger plug and orifice) and it was a bit sooty, but not bad.

[carsy]

I used to get this on mine. No amount of cleaning solved it. I bought a new one which worked fine for a month or two then that also reverted to holding the revs high.

In the end i got the engine up to temp and when it had a nice idle at the correct rpm i disconnected the wiring plug to the damn thing. This solved it.

Finally though did as Pup did and went Emerald with no idle valve at all.

[blitzracing]

WokingWedger said:

Yes its a good write up, thanks.

I note he also says 'When the car stops, the road speed signal will
also stop and about 2-3 seconds later the ECU will enter idle mode
and start to reduce the engine revs.'

This is what is annoying. This delay, and when crawling at 5 mph having high revs.

He also states 'When the throttle is released, the ECU will not attempt
to bring down the revs because the car is moving.
This means that the revs are kept higher during a gear change to help
prevent rear wheel lock up and that the ECU will only go down to
the low idle speed if the throttle is below the idle threshold and there
is no road speed signal.'

I don't want the revs held high when changing gear ! If I did I wouldn't bother taking my foot off the throttle.

Both the above are by design when everything is working as it should.

Its far from ideal !


I cleaned my stepper (plunger plug and orifice) and it was a bit sooty, but not bad.

The uplift is only about to 1200 rpm, so hardly a big deal between gears, or did you see more than that?