Shunting/power loss

Shunting/power loss

Author
Discussion

blitzracing

6,387 posts

219 months

Monday 27th June 2016
quotequote all
It is smart enough to do a stepper reset every time you switch off- it does this by sending 255 pulses to a motor that only has 180 steps, so it hits the end stops, (thats the buzz you hear from the plenum) so the ECU can start from known stepper fully open position next time you start the car. Not quite closed loop, but it does give a reference point.

ChimpOnGas

9,637 posts

178 months

Monday 27th June 2016
quotequote all
davep said:
ChimpOnGas said:
.... it's over complicated and complication can add unreliability. My Canems system has a closed loop system that controls idle via a two wire Bosch type extra air valve ....
That's the crux of the matter! I don't think complexity wrt reliability is a major factor but the fact that the ECU or code doesn't actually know where the stepper is due to no direct feedback, it's open loop rather than your closed loop. The Stepper Motor control code only has the last value of a step counter to use as a control reference. However, I've found that with all the related sensors working correctly and with base idle set at the optimum level the 14CUX stepper/idle function works just fine.
I agree, it does work well with all the related sensors working correctly and with base idle set at the optimum level, but you could say that about all such systems (mine included).

Anything can fail but I think in the TVR application the 14CUX problems are compounded by seven key areas:

1. The age of the 14CUX system

2. The shockingly bad way TVR mounted the ECU, or rather didn't mount it (just wedged between the battery and one side of the foot well)

3. The age of the ECU's associated engine sensors

4. The age of the wiring loom that TVR sourced from Land Rover

5. The areas where TVR joined their own loom to the Land Rover sourced ECU and engine bay loom

6. The poor quality of TVR's own electronics in the 90's (speed signal splitter)

7. The extremely high levels of under bonnet heat on the TVR application (forward path exhaust manifolds ect), heat that gives the sensors and wiring a really hard time

I have a friend with 5.0 litre Chimaera on the venerable old 14CUX that idles perfectly and suffers no shunting whatsoever, and its fair to say they wouldn't have sold many Chimaeras and Griffs back in the day if the fuel management & idle management system wasn't capable of delivering a smooth drive.

But the truth remains today's Chim/Griff owner needs to accept the seven above additional areas of potential failure are not stacking the reliability cards in their favor, it all adds to the argument of fitting a more modern and user accessible/adjustable engine management system that also controls ignition.

Forget for a minute the drivability, fuel economy and throttle response improvements such fully mappable stand alone engine management systems offer, the new engine bay & ECU loom that comes with it will by itself eliminate a big slice of potential issues on these aging cars.

And unfortunately.... that's a fact yes

Chimp871

Original Poster:

837 posts

116 months

Monday 27th June 2016
quotequote all
Chimp - I understand any of those reasons could kick in but laying up a car, change cam and then have power failure is hard to put down to various tvr quirks or gremlins.

Besides iffy design, controversially, I feel the servicing garages are part to blame for not pointing out points to fix improve on. I read somewhere over 50% of chimps are on SORN

Bassfiendnoideawhathp

5,530 posts

249 months

Monday 27th June 2016
quotequote all
Chimp871 said:
I read somewhere over 50% of chimps are on SORN
I suspect that percentage will vary massively between winter and summer - mine was always a daily driver and works for its living, it stays outside and is used in all weathers, but I suspect that it is very much in a minority and I bet a good portion of them are taken off road and SORN'd over winter... smile

TV8

3,118 posts

174 months

Monday 27th June 2016
quotequote all
blitzracing said:
It is smart enough to do a stepper reset every time you switch off- it does this by sending 255 pulses to a motor that only has 180 steps, so it hits the end stops, (thats the buzz you hear from the plenum) so the ECU can start from known stepper fully open position next time you start the car. Not quite closed loop, but it does give a reference point.
My last car stopped doing the stepper motor reset thing and had cold start and very lean running. Changed the pattern AfM for a genuine Lucas one and all was good. Don't under stand why but if you have anyone local with a spare or even swap one temporarily from a car that is running fine and it will be a easy test.

QBee

20,904 posts

143 months

Tuesday 28th June 2016
quotequote all
davep said:
blitzracing said:
It is smart enough to do a stepper reset every time you switch off- it does this by sending 255 pulses to a motor that only has 180 steps, so it hits the end stops, (thats the buzz you hear from the plenum) so the ECU can start from known stepper fully open position next time you start the car. Not quite closed loop, but it does give a reference point.
Yep, it also does the same reset procedure when the Inertia Switch is activated and for any event initialising the Shutdown Sequence.
Mental note to self - must remember to listen out for this next time I enter the Mallory Park gravel trap sideways at speed. That's the only time I have activated the inertia switch. idea

ClassiChimi

12,424 posts

148 months

Tuesday 28th June 2016
quotequote all
The trouble You'll have there Anthony is all you'll be hearing is the sound of pea gravel,,,, I should know, I've heard it enough times myself. hehe

I once activated my fuel stop switch by banging the dash top when my heater control was intermittent,, I can't say as I heard anything from the stepper at the time but then I probably wasn't listening for it!

Chimp871

Original Poster:

837 posts

116 months

Thursday 30th June 2016
quotequote all
update:

Rovergauge plugged in and working well (nice bit of kit too).

Fault codes thrown were 17 (throttle pot) and 19 (hi flo MAF and throttle pot).
Reset codes & reset ECU.
Back in car and went to set off but fault 17 showed again and would not clear
Went for drive to get to power loss problem, but I noticed throttle position does not move off 11% mark (non adjusted) whilst driving.

So the throttle pot looks knackered but before I go and get one is a broken throttle pot consistent with such power loss?

I did log it all but it's in txt file format which looks weird.

Edit - from this post i!may be getting close. He had 11% (and not moving) and limp home mode too
http://www.pistonheads.com/gassing/topic.asp?t=126...


Edited by Chimp871 on Thursday 30th June 11:04

TV8

3,118 posts

174 months

Thursday 30th June 2016
quotequote all
for the log files save as csv file and import with excel into table with headings

davep

1,141 posts

283 months

Thursday 30th June 2016
quotequote all
TV8 said:
for the log files save as csv file and import with excel into table with headings
There's no need to save as .csv, the Excel Text Import Wizard detects that the RoverGauge log file (<date:time>.txt) is delimited with commas.

Quick procedure:

Use Open and select the log .txt file and Excel will automatically open the Text Import Wizard, the Delimited button should be selected.
Click Next to Page 2 and select Comma in the Delimiter list.
Click Next for Page 3, click Finish.

The log data is now displayed in correctly formatted columns. To get the best presentation use Excel's Home command line and select Cells/Format/AutoFit Column Width.

Chimp871

Original Poster:

837 posts

116 months

Thursday 30th June 2016
quotequote all
got it thanks.... TPS is a constant 11% (also lambda's are at zero).

Focusing on TPS and link above explains ecu can get stuck

Englishman

2,215 posts

209 months

Thursday 30th June 2016
quotequote all
As you have been working on the engine, I'd check the throttle pot wiring and connectors for continuity before buying a new one.

Chimp871

Original Poster:

837 posts

116 months

Thursday 30th June 2016
quotequote all
Gives you an idea of RG results. You see the throttle pot stuck at 11%.

I'm getting 4.9v at the TP connector engine side.
Throttle pot shows 6k ohms but doesn't budge when rotating.


blitzracing

6,387 posts

219 months

Thursday 30th June 2016
quotequote all
The throttle pot wiring is simple enough- around 5 volts at one end, ground at the other, and the central wiper goes back to the ECU, so it sees a swing of just above 0 volts to just under 5 volts from min to max throttle.

The wiper output wires is the red wire (+ve ) and green ground (-ve).

If you have a fixed resistance with it unplugged across red and green as it moves its definitively Fubar.

davep

1,141 posts

283 months

Thursday 30th June 2016
quotequote all
A few comments:

Your throttle pot appears to be shot, the resistance track/wiper is stuck and showing maximum value.

The Main Voltage values are low, which will cause the ECU to extend the fuel injector pulse width. Look to your battery/alternator.

The Fuel Map Column and Row values should be whole numbers, e.g. Column 3, Row 2.

The ECU is running with Fuel Map 5, closed loop, but there are no Lambda Trim values, this could be a connectivity problem or your car has been de-catted and the probes removed/disconnected.

Note that your road speed shows max 33 MPH so you have the TVR speed signal splitter module fitted.

Apart from that it looks fine wink

Chimp871

Original Poster:

837 posts

116 months

Thursday 30th June 2016
quotequote all
davep said:
A few comments:

The ECU is running with Fuel Map 5, closed loop, but there are no Lambda Trim values, this could be a connectivity problem or your car has been de-catted and the probes removed/disconnected.
hmm...they are both connected. Battery is low due to amount of starts whilst testing, but will charge and check.

just scraping myself off the floor after seeing how much tps are!!! £150.. frown

edit - it seems my TPS is a pre-serp version despite having a serp engine!#. Current knacked one is stamped 215SA, variant 70408A a lucas part(LR - ERR2263).

£130 for original serp one from tvr parts - http://tvr-parts.com/tvr-parts/part-details/tvr-e0...

Just for fun I rang LR dealer who said it was £280 + vat........

Will come back if it sorts my problem out.... but pleased ecumate shows TPS problems as throwing car into limp mode




Edited by Chimp871 on Thursday 30th June 15:15


Edited by Chimp871 on Thursday 30th June 15:21

blitzracing

6,387 posts

219 months

Thursday 30th June 2016
quotequote all
Still too much- but better:

http://www.rimmerbros.co.uk/Item--i-ETC8495A

Edited by blitzracing on Thursday 30th June 16:14

Chimp871

Original Poster:

837 posts

116 months

Thursday 30th June 2016
quotequote all
Blitz - you appear to be a guru on electrics, when i get a new tps do you want old one to break apart and see fault?

blitzracing

6,387 posts

219 months

Thursday 30th June 2016
quotequote all
Chimp871 said:
Blitz - you appear to be a guru on electrics, when i get a new tps do you want old one to break apart and see fault?
Im game for that, ill drop you my address. I did spend some time trying to find an equivalent, I thought it would be easy- after all, its only got to go from around 0 volts to near 5 in just over 90' but how wrong. The MGTF one will fit the stud placings, but its sweep is about 120' so you cant get enough voltage at the 90' point (WOT) with a 5 volt supply. The fix is to supply the pot with a higher voltage to start with from the injector rail, but that means two lots of plugs connected to the TPS and the cost of the conversion goes up, and they don't fail in high enough quantities to make it financially worth while to make a kit up.


Heres the AES one:

http://www.autoelectricalspares.co.uk/lucas-seb201...

Edited by blitzracing on Thursday 30th June 21:23

Chimp871

Original Poster:

837 posts

116 months

Monday 4th July 2016
quotequote all
blitzracing said:
Still too much- but better:

http://www.rimmerbros.co.uk/Item--i-ETC8495A

Edited by blitzracing on Thursday 30th June 16:14
Blitz - would you know which is +ve, -ve and trace wire from link you sugested - which is coming tomorrow?