T5 power loss under acceleration

[zodski]

Thanks for that Simon...I'm beggining to wonder if fuel might be an additional problem for the following reasons.

I've just filled the tank up (max, done last night). This morning, the car was full of petrol smell / fumes, like I've never had before. I took the car out in the hot weather, ran fine to start with (as described earlier), but when we got caught in a massive tail back on the A17 due to an accident, the car idled for about 5 - 10 minutes, then ran very rough, then stalled. Attempts to get it started were initially futile, as all that happened was that the engine caught, reved to 1500rpm, then fell back to about 400rpm, despite what I did with accelerator, then stalled. All in about 5 seconds. I managed to get it going after it had stood in the shade for about 20 minutes, but again the same thing happened on the way home - got caught in traffic, engine ran rough, then stalled. I manged to get to a carpark (where the car is still is), and let it rest for half an hour. Unfortunatley, it was in the sun, and temps are soaring towards 30C here is Sleaford. Further start attempts repeated what happened earlier - started, ran to 1500rpm, fell back to 400rpm then died, all in a short time. COuld the smell and this instances be caused by vapour locks or something?

Taking this with the smell of fuel, and the fact that during acceleration the car kangaroo hops, I wonder if this could be caused by a fuel problem? My understanding is that, if the engine cannot develop enough torque, the ECU doesn't allow the turbo to kick in. Is this correct? Could a lack of torque be due to fuel starvation (my gut feeling is yes, but I don't know enough about this system - yet!)?

So Simon, I think I might try your method of checking the fuel pressure. I will take care, its just that I still cann't afford garage bills.

[sholtby]

Something else to check is the condition of the spark plugs, rotor arm and plug leads. Check the leads are on the correct way round. A blocked fuel filter could also b the culprit.
You shouldnt have a smell of fuel as the system is sealed on modern cars.
Next time you drive the car though and it fails to start try removing the fuel filler cap and then refit it. There may be excessive pressure or vacume in the tank if things arent working correctly.

Quote..
My understanding is that, if the engine cannot develop enough torque, the ECU doesn't allow the turbo to kick in. Is this correct?

I dont think that is correct
Quote..
Could a lack of torque be due to fuel starvation (my gut feeling is yes, but I don't know enough about this system - yet!)?

A lack of torque/power could be due to too little or too much fuel, an ignition problem, an electrical/electronic problem or a mechanical problem eg low compression

Simon

[zodski]

I looked at this one this afternoon, and compared it to the spares diagram I've got from elsewhere on this site. I'm now confused.

When I inspected the original pipes to the turbo boost control valve, they were colour coded at each end, red, blue and yellow. These colours matched three paint marks on the valve, the yellow, at the top, going to the actuator, the blue in the middle going to the pipe just after the MAF sensor, and the red (incidentally with a '-' symbol next to it), at the bottom going to the sensor on the compressor side of the turbo. When replacing the pipes, I used cable ties at each end as markers, and am certain that I got them right.

However, looking at the diagram in the Parts guide off the site, the yellow and red appear to be swapped, but I'm not sure if I'm looking at the sensor in the correct orientation. Is there a definitive guide to which way round they should go, using the '-' symbol on the sensor body? I know I've got the blue (MAF) pipe right, but am now seriously worried that I've got the other two wrong.

Thanks in advance.

The red dot should have a pipe to the turbo compressor, and the yellow dot should have a pipe to the actuator. Blue goes next to the MAF.

Adam.

[zodski]

Sadly, my car is a '96 version. I understand that this is slap bang in the middle of two resetable version (cars to '95 with the engine bay code reader, cars '97 and after with OBDC II which can be reset from the ignition/trip reset switch). As far as I'm aware, not even pulling the battery for a couple of hours will reset - only a set number of correct engine cycles will 'demote' the warning and trip it off, or using a reset tool (which I don't have) will clear the codes.

Am I correct with this understanding?

[imac]

I know this may sound silly, but are you 110% sure all the pipes are on the right way? Someone on an American board had similar trouble when reconnecting the vac pipes on the turbo incorrectly.

[Chris_Rogers]

>Sadly, my car is a '96 version. I understand that this is
>slap bang in the middle of two resetable version (cars to '95
>with the engine bay code reader, cars '97 and after with OBDC
>II which can be reset from the ignition/trip reset switch). As
>far as I'm aware, not even pulling the battery for a couple of
>hours will reset - only a set number of correct engine cycles
>will 'demote' the warning and trip it off, or using a reset
>tool (which I don't have) will clear the codes.
>
>Am I correct with this understanding?


I think you are confusing the Service light with the Lambda Light.

Reset the codes and Lambda (MIL) light using the LED / Switch as described in the link.

1. Read codes twice

2. Push switch for about 5 secs

3 Wait until LED lights again, push switch again for 5 secs+ BEFORE the LED goes out.

[zodski]

I am pretty sure that, when replacing the pipes around the turbo, I kept them marked correctly. Also, my routing of the pipes appears to tie in with Adam's guidance (red to compressor, yellow to actuator and blue to MAF). However, out of desperation and with a bit of experimentation, I have swapped the yellow and red at the turbo boost control valve.

Having driven the car, it ran a lot better - there was no kangaroo hoppping around 2500 - 3000rpm, the engine doesn't dip to 300rpm in idle, and there is a much better engine response to the accelerator (I can get to 5000rpm without slowing down - it still takes a bit of time to accelerate). The turbo indicator in the car now moves about 5mm into the white under acceleration, even though there isn't the response that there used to be. Whilst accelerating, I THINK I can hear a very quiet hiss from the engine bay, but I can't reproduce this with the hood up - am I inventing a slight leak?

So, two questions on this particular theme:

First, what exactly does the boost control valve do? Wouldn't swapping the pipes reverse operation of the turbo (open the wastegate at high revs etc, which doesn't appear to be happening)? Would swapping the pipes affect the turbo / engine to such an extent that the engine can be damaged?

Second, how can I reproduce the engine running under load to see if there is a leak? I can accelerate the engine, but short of putting it in gear against the handbrake and chocks, I cannot see how I can do this safely.

[zodski]

Sorry Chris for my lack of clarity.

My '96 855 doesn't have the engine bay readout, so I cannot rest from the engine bay as suggested. I have to do my resets for fault codes via the OBDC II infront of the gear selector, and I don't have a reset gadget, so can't clear the codes....

>
>Second, how can I reproduce the engine running under load to
>see if there is a leak? I can accelerate the engine, but short
>of putting it in gear against the handbrake and chocks, I
>cannot see how I can do this safely.

Put the car on a rolling road. That's precisely what it allows you to do.

Adam.