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Hi All
On Wed 4/8/10 I had a good journey as far as Lincolnshire (150miles) and was travelling at about 50 mph when the engine lost power (as if I had taken my foot off the accelerator). I managed to keep going albeit at 15 – 20 mph and crawl about a mile from the bypass into Long Sutton. On the odd slight slope I had to disengage the clutch, nurse up the revs, and let the clutch back out to keep going. I was recovered from there to a garage about 15 miles away (although 150 miles from home), which used to be MG Rover agent and still had and used the T4 diagnostic computer. They fortunately also still stocked parts. On arrival the engine would start, but would not rev and had no power to move the car.
My car (had since new) was first registered in Sept 2004, a facelift model, has done 64K miles, and it’s been regularly serviced by a MG Rover specialist in my area. The only non routine parts replaced have been the cooling fan, and the rear springs. At the last service (April at 62K miles - a C service) they reported that the fuel tank pump was slow in building up pressure and I might eventually have trouble in starting (but I haven’t to date), and it eventually would need to be replaced.
In Lincolnshire the T4 reported low fuel pressure as expected (tank about a third full), and the tank pump was replaced and expected to cure the problem. The engine however ran much as before - would start after 2-3 turns (used to be 1st half turn), and seemed very sluggish and lumpy. If you put your foot down it cuts out, if you nurse the throttle it will pick up revs and keep going for longer, if you leave it to idle it dies - i.e. all largely as before the pump was replaced. No faults on the T4. The fuel pump delivery pressure was now 400kpa, and that after the injection pump 30,000kpa which I’m told is well on spec. Further testing, diagnosis and part substitution ensued.
The following parts were replaced to no effect, removed and could then most fortunately be returned to stock (T4 readout seemed to confirm all working also).
MAF (Bosch), fuel filter head, bothfuel pressure sensors, camshaft sensor, crankshaft sensor. The crankcase PCV checked OK.
The injection nozzles/solenoids were then removed and sent to a specialist, where they were cleaned then tested, found to be fine, and refitted. The exhaust was then disconnected to eliminate blockage of the cat etc and the engine run – no improvement. Finally last Thursday as all other options had been exhausted, the EDC (showing no signs of water damage or other symptoms) was removed and sent to another specialist (who offer a full check and if necessary repair service). On contacting the garage this morning (Sat) they had just been told it had passed all tests and hence was not faulty.
Last Thurs I found the excellent tuning-diesels.com website, in particular the sections on the BMW M47R engine and on the Bosch EDC15L series Injection system and told them about it. When the EDC arrives back on Monday this will be systematically worked through as a cross check.
If anyone has experienced similar symptoms and solved the root cause, or has any ideas we would be very grateful for your help as we are running out of ideas.
Many thanks Andrew JH
 

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It does sound like the pedal potnetiometer has failed, A replacement pedal would likely solve this problem.

Richizt on here had the exact same symptom and i swapped my pedal for his to solve the mystery of why it would not rev.

Simon
 

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oi , awkward arse you know what i meant .
Threads need a result so that we can all learn how to help others with the same problem .
Git si . Lol

FLYER.
Actually no I didnt see what you meant flyer, thats why I was confused.

Had it been on a thread about locking threads then I would have got it, however the correlation between what I posted and your post did not make sense to me, but now it does.
Simon
 

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A certain lady member (not poppy) once opened 4 threads over a 6 month period and didn,t post one single result .
The next time she posted a question i asked her when was she going to give a result for the other threads ???
She then said to me that instead of asking that why didn,t i try helping with her latest problem ????.
Nuff said .

FLYER.
 

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A certain lady member (not poppy) once opened 4 threads over a 6 month period and didn,t post one single result .
The next time she posted a question i asked her when was she going to give a result for the other threads ???
She then said to me that instead of asking that why didn,t i try helping with her latest problem ????.
Nuff said .

FLYER.
She can Foxtrot Oscar then. Can't bloody abide people like that, who think they have the right to call on others as if they were their own personal pit crew.

People on here give help through the goodness of their hearts, and some gratitude for the same never goes amiss.
 

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If i,m reading a thread that might help someone from the archive i jump to the end now to see if there was a result, if there was no OP closure i dont bother reading the thread .
I once read 4 pages on something and it went stone dead , that does my head in .
BTW OP if you do come back we will forgive you lol

FLYER.
 

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dont the 75 have a backup petentiometer then?

some newer cars have a primary and secondary, and the cars ECU compares the readings.. if they are different it logs a fault.. just a safety so that in the event of failure of 1 of the petentiometers the car doesnt loose its accelerator.
 

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dont the 75 have a backup petentiometer then?

some newer cars have a primary and secondary, and the cars ECU compares the readings.. if they are different it logs a fault.. just a safety so that in the event of failure of 1 of the petentiometers the car doesnt loose its accelerator.
Hi,

Yes,they have ;

i read:
The APP sensor consists of two resistance tracks and two sliding contacts,effectively a pair of potentiometers,connected to the accelerator pedal assembly.
The use of a pair of identical sensing elements ensures a position signal is still provided even if one of the sensing elements develops a fault.

Cheers

Mike
 

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Hi,

Yes,i read:

The APP sensor consists of two resistance tracks and two sliding contacts,effectively a pair of potentiometers,connected to the accelerator pedal assembly.
The use of a pair of identical sensing elements ensures a position signal is still provided even if one of the sensing elements develops a fault.

Cheers

Mike
so wouldnt that throw the original idea about it being the petentiometer out the window?

as I would of thought as soon as the primary track fails.. it wouild of triggered the engine light... and it would of been unlikely that it ever got to the point of the 2nd track simultaneously failing as well.
 

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so wouldnt that throw the original idea about it being the petentiometer out the window?

as I would of thought as soon as the primary track fails.. it wouild of triggered the engine light... and it would of been unlikely that it ever got to the point of the 2nd track simultaneously failing as well.

More info before replacing the part:

The pedal demand sensor signal is proportional to the accelerator pedal position.The ECM provide a 5 volt supply to both potentiometers and receives two input signals back,one from each potentiometer.
At idle,throttle released (0° throttle angle),potentiometer one wil return approximately 0.7 volts,
whilst potentiometer two will return approximately 0.4 volts.
As the throttle angle increases,the voltage of each potentiometer increases to a maximum of 4.2 volts for potentiometer one and 2.1 volts
for potentiometer two.the two potentiometers operates simultanously in response to accelerator movement.The ECM receives an analog signal from the throttle position pedal sensor and monitors the throttle angle for plausibility
The ECM calculates the maximum allowable fuel quantity from:
-Air flow into the engine
-Engine speed
-Temperature

It would be interesting to take a measurement of the two voltages.

Mike
 

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dont the 75 have a backup petentiometer then?

some newer cars have a primary and secondary, and the cars ECU compares the readings.. if they are different it logs a fault.. just a safety so that in the event of failure of 1 of the petentiometers the car doesnt loose its accelerator.
Hi,

Yes,they have ;

i read:
The APP sensor consists of two resistance tracks and two sliding contacts,effectively a pair of potentiometers,connected to the accelerator pedal assembly.
The use of a pair of identical sensing elements ensures a position signal is still provided even if one of the sensing elements develops a fault.

Cheers

Mike
so wouldnt that throw the original idea about it being the petentiometer out the window?

as I would of thought as soon as the primary track fails.. it wouild of triggered the engine light... and it would of been unlikely that it ever got to the point of the 2nd track simultaneously failing as well.
More info before replacing the part:

The pedal demand sensor signal is proportional to the accelerator pedal position.The ECM provide a 5 volt supply to both potentiometers and receives two input signals back,one from each potentiometer.
At idle,throttle released (0° throttle angle),potentiometer one wil return approximately 0.7 volts,
whilst potentiometer two will return approximately 0.4 volts.
As the throttle angle increases,the voltage of each potentiometer increases to a maximum of 4.2 volts for potentiometer one and 2.1 volts
for potentiometer two.the two potentiometers operates simultanously in response to accelerator movement.The ECM receives an analog signal from the throttle position pedal sensor and monitors the throttle angle for plausibility
The ECM calculates the maximum allowable fuel quantity from:
-Air flow into the engine
-Engine speed
-Temperature

It would be interesting to take a measurement of the two voltages.

Mike
All very interesting information regarding the accelerator pedal guys.

However myself, Richizt and OhNoItsD (formerly damienp) have all witnessed complete failure of the accelerator pedal on Richizt's car with no real warning that It was on it's way out. Hence the reason I suggested may be a possible culprit.

I'm not 100% sure but I think his engine check light may have been illuminated, but I honestly can't remember.

On my scan tool no fault codes were logged, I assume only a T4 would be able to give this information, however with my scan tool we were able to see that the throttle position was 0% while the engine was running and pressing the accelerator hence the decision to try my pedal out of my car. which solved the problem of it not revving. My scan tool does pick up some DTC codes on my car to be fair though.

As there was a backup circuit it seems odd that both should have failed at the same time, or that one had failed for a while and the other finally gave up the ghost too.

Simon
 
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