T5 power loss under acceleration

[Chris_Rogers]

>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....


Yes you can, use the LED and switch you have made, as I described.
The Engine ECU and the method of reading and resetting codes is exactly the same as the older system in the engine bay.

[zodski]

Chris

Sorry for being so boneheaded. Thanks for the help, and I'll have a go at getting it done as soon as possible.

[zodski]

I've done as you suggested - read and cleared the codes.

After about 30 to 40 miles of driving (some town, but mostly open road) the CEL comes on. The code that is given is 2-3-1. As I've got a new MAF and no 1-2-1 code, I'm assuming I can ignore problems from this area. I'm going to check fuel pressure (as suggested by the information provided else where on this site for 850 fault codes). Sensors, are, I think, OK. I might be over interpreting the information on the club site, but does a 2-3-1 mean 'Partial Load Range' and 'Lower Limit (rich fuel / air mixture)', and hence should I be checking for HIGH fuel pressure and / or leaking injectors? Could leaking injectors be the cause of the fuel smell that I get when I fill up the tank? I've also noticed that, with the windows down and driving along (therefore not smelling the exhaust) there is a very strong smell of fuel from the engine bay.

I've also followed Adam's and bobcats' suggestions by checking that there was no leak in the turbo indicator line, and then disconnecting the wastegate vacuum tube. I went out for a drive, first gentle, and then down the bypass. I got a response on the indicator in line with the throttle until a slight positive pressure was indicated, when it just sat still. If I floored the accelerator, the indicator went about half way into the white band, but the engine response was 5000rpm but no power, almost exactly the same as when the pipe was connected. This means, I suppose, that the wastegate actuator is frozen in position.

As I have been having doubts about the turbo itself, I reconnected the actuator pipe and disconnected the engine air supply just after the intercooler. At idle, the engine continued to run until I put my hand over the air pipe from the intercooler, when the engine then cut out. I would expect this, as the MAF would detect zero airflow. There was a slight positive air pressure from this pipe - again, as I would expect with a low idling turbo. When I applied power to the engine, the air from the intercooler nearly blew my hair off - again, just as I would expect with a turbo running under load.

So, I take it that I need to look at the wastegate actuator. How can I clean / check this? Is it possible? Is anything else suggested by these symptoms that I ought to be considering?

As ever, any help and advice is always welcome and wanted.

zodski

[zodski]

Latest installment - and a couple of questions.

First, after much headscratching about my constant power loss and having checked it out under load (when I could hear a leak), I decided to totally disassemble all the turbo components, from intake through to inlet manifold. After rigourous inspection, I found a small crack behind a badly placed o-ring on the connector pipe from the turbo body to the metal pipe going over the engine to the intercooler. Replacing the part means that I now have steady acceleration over the whole range of revs (no more kangaroo hopping). However, I now get one of the following situations occuring when accelerating - either high boost indicated (about 2/3 into the white band) with high revs but no acceleration or low boost (about 2mm into white band) with steady acceleration (30 to 70mph in about 15 seconds, lumpy gear change on the auto box, but steady cruise at 70). Following earlier suggestions, and looking at the Tech section of the site, I have checked the fuel pressure - I think.

This is the first of the questions. The Section F - Basic Testing manual says to connect a pressure gauge between fuel line and fuel rail. I checked my pressure on the Schraeder Valve at the end of the fuel rail instead. Is this okay? I cann't see any pressure reducing gizmos in the drawings or on the car so feel that this ought to be alright. My measurement of the pressure at this points indicates a fuel pressure of 19psi, way below the 43.5psi that the book states. As I had a new pump fitted (I thought) at the beginning of the year following the failure of the previous one, I hadn't expected such a poor value. When I pinched the return line, the pressure remained static, indicating a knackered pump. This might explain the persistant 2-3-1 code, which seems to occur whenever the engine is put under load - exhaust mix too lean, so ECU commands more fuel outside of limits and sets fault flag. I cannot find a way of adjusting the output of the pump anywhere. Is this possible ie can I tweak a variable resistor to boost pressure? Do I need to replace the pump, or is there some work that I could do to bring it into spec? If not, where can I find out how to replace the pump?

My other question is one that centre's on the fuel computer. I fill the tank up, and with a full tank of 15 plus gallons, will get 320 to 360 miles, depending on conditions. I reckon this gives me an mpg of around 21. However, the computer sticks stubbornly to 16.5mpg, and mucks up all the fuel and distance predictions. Whilst not a killer, its annoying getting the Fuel Low light on when there are about 5 gallons of fuel (100 miles) left in the tank. Is this because of my present problems - ie is the figure calculated by information that the ECU provides, as opposed to raw data - or is it an indication of something else begining to go wrong?

Thanks for all your help so far - my T5 is beginning to act more like it used to, but there is still some way to go!

Hi

I'm new here as well and read your post and the replys with great interest as I have a manual '96 T5 which has the same symptoms. I took it to the my local Volvo main dealer and they replaced a piston, and charged me handsomely. This didn't solve the problem and as soon as the car had warmed up the symptoms returned, I returned my car to the dealer and after 3 weeks of alledgly trying they decided they couldn't fix it.. without X-Raying the engine !?.

Anyway it's now with an independant garage and my cc company is chasing the dealer for the cash. Thought I'd share, and say thanks to all who have posted here gives me some tips for the independant garage. Unfortunatly I'm not in a position to do the work myself.

Thanks and best regards.
S

[Chris_Rogers]

The fuel pressure should be 300kPa (43.5 psi) above the manifold pressure.
So your 19 psi (131 kPa) figure is low but was the engine running at idle?
If so the fuel pressure will be lower by the amount of vacuum but it should not be that low.
When was the fuel filter last changed?
Access to the fuel pump is via the luggage space under a circular metal cover. The pump and fuel level sensor is in one unit. the pump can be replaced separately. I think the Haynes manual covers this.

The fuel computer takes info from the engine managemnt ECU this would assume fuel pressure was correct and calculate use on the basis of integrated injector open time. If the fuel prssure is low then it would over estimate fuel useage.

[zodski]

Thanks for that Chris - a great help.

The engine was at idle, but I must admit I was suprised myself about the low value...thanks for confirming that. Also, a relief to know that the low mpg is a result of the ECU's confusion!

I'll be looking at the pump next.

[zodski]

Final installment?

Following Chris's help, I took the fuel pump out today, and gave it a once over. As I exercised the motor in the base of the body, I noticed that the flexible pipe between the pump itself and the fuel supply port tube was moving easily with the pump, and at one stage actually popped off the tube, despite the clamping ring. My immediate reaction was that this is where my pressure was going - a small amount on the supply, but the rest just passed back into the tank!

I tightened up the clamp (obviuously left loose from when the pump was replaced at the beginning of the year) and checked the pressure - 39psi at idle. I took the car out for a spin, and, joy of joys, my performance is back! I can now hold my head high at the traffic lights once again! And the trip computer is telling a proper story again.

Now, for a load of minor problems to fix (rear wiper, engine mounts, headlight wipers to name but a few) that have been put off whilst all this has been going on.

Thanks a lot for all your help out there - it has really been a tremendous boost, both to my moral and my knowledge of the car. Next, I'll be trying to find out how to upgrade the turbo, what does 're-mapping' actually entail, and what do I need to do to get that little bit extra. What a prospect for someone new to this business of performance cars! Thanks again.

[IC]

Stephen, glad that you've sorted the problem. The performance section has monthly meets - there's one this Sunday at the Crooked Billet near Uxbridge/Slough. The meets are very well attended and if you did get a chance to attend one Sunday you would get a chance to chat to people about their upgrades and go out in their cars to experience the affect of different modifications - there's information on how to get there above this thread. I know it's a bit of a drive, if you could make a meet you would be very welcome!