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rough idle especially in reverse with wheel turned to the right

Help, Advice, Owners' Discussion and DIY Tutorials on the Volvo S80 model. Sometimes called an "executive car", the S80 was and continues to be Volvo's top-of-the-line passenger car.
hu5ker555
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rough idle especially in reverse with wheel turned to the right

Post by hu5ker555 » Sat Nov 09, 2019 3:47 pm

2005 S80 2.5T

My S80 has a rough idle and will sometimes stall out, especially if it's in reverse and the wheel is turned all the way to the right. I've pulled codes and there is a P0101 and P2188...probably a small vacuum leak somewhere but haven't been able to pinpoint it. Not sure why the reverse and wheel turning would make things worse, and even stall the vehicle. Any suggestions appreciated.

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Re: rough idle especially in reverse with wheel turned to the right

Post by jimmy57 » Sat Nov 09, 2019 4:15 pm

Check motor mounts and the orque mount and look at the hose that comes from MAF sensor to turbo inlet. The motor moves a different way fore-aft for reverse and the engine moves left -right due to steering rack being on the subframe and subframe mounting the car body with rubber bushed mounts. You may be opening a crack in the MAF to turbo hose and the MAF signal goes low and fuel quantity is cut. If you unplug the MAF and then start engine and the probllem is gone that confirms it but will set a fault code. WHen the MAF is unplugged the ECM runs a default program not needing the MAF input.
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hu5ker555

hu5ker555
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hu5ker555

Re: rough idle especially in reverse with wheel turned to the right

Post by hu5ker555 » Mon Nov 11, 2019 8:22 am

Thanks for the good ideas there. I'll look more closely at the MAF to turbo hose, especially with the car in reverse and wheel turned fully. Maybe I'll detect some hissing sound or could spray some carb cleaner around there and see if it changes the idle.

If that doesn't help, I think my next step might be to smoke test with a cigar. Was thinking I would put a rubber glove on the intake hose just downstream from the MAF, stick a rubber hose in one of the fingers, and puff cigar smoke down the hose.

Also...just curious...you mentioned that if I unplug the MAF the problem might be gone but it will set a fault code. If this happens, is there harm in driving the car with the MAF always unplugged?

hu5ker555
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hu5ker555

Re: rough idle especially in reverse with wheel turned to the right

Post by hu5ker555 » Sun Jan 26, 2020 4:30 pm

So I smoke tested and found the general location of the vacuum leak. It is somewhere at the base of the large intake hose if you follow the intake to where it turns 90 degrees towards the motor. I think this is where the PTC is located. There appear to be a couple of connections to this hose where it turns towards the motor. Not exactly sure where the leak is, but it is somewhere in this location.

Any suggestions?

I can see where I could potentially remove the hose clamp where it enters the motor and then pull off the hose, all from underneath the motor. However, there are a couple of other hoses that connect to it at the base and they don't appear to be easily disconnected and not reachable. There may also be a wire connection there. Not sure how I would get it all apart and back together again. Very difficult to access this area. I've read that these small hoses are crimped onto the intake hose and not meant to be re-done.

Was thinking of going to a junkyard to see how it all fits together, and maybe see if I could somehow disconnect the other small hoses and wire at more accessible locations.

hu5ker555
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Re: rough idle especially in reverse with wheel turned to the right

Post by hu5ker555 » Tue Feb 04, 2020 7:16 am

So I went to the junkyard and successfully removed a couple of these turbo intake pipes. I had to remove the airbox, battery feed cable, and bundle of wires connected to the fuse box. Then I was able to loosen the banjo clamp from underneath and wiggle the intake pipe out while disconnecting the three hoses from the base of the intake pipe and the electrical connection. It was a bear.

Now for the double-bear of putting one of these back into my own vehicle and hoping that it fixes the problem. Any thoughts/advice appreciated.

hu5ker555
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Re: rough idle especially in reverse with wheel turned to the right

Post by hu5ker555 » Tue Feb 04, 2020 4:17 pm

I've attached a photo of the intake pipe that I obtained from the junkyard. The red pen is pointing to an apparent orifice in the side of the PTC. However, this orifice appears to either be blocked off intentionally or maybe it is clogged. Should this orifice be cleaned out or drilled open? I don't recall there being a hose attached to this orifice, so I'd be concerned about opening it up without having a hose connected to it. I know the other three hoses need to be connected along with the electrical connection.
PTC orifice.jpg

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Re: rough idle especially in reverse with wheel turned to the right

Post by abscate » Tue Feb 04, 2020 6:23 pm

The PTC is just a hole in a metal plate. The electrical connection heats it to keep it clean of cold crud.

The part where you have your pen needs to be closed, correct.

Did you pull out the PTC orfice and inspect it?
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hu5ker555
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Re: rough idle especially in reverse with wheel turned to the right

Post by hu5ker555 » Tue Feb 04, 2020 6:33 pm

Thanks a ton for getting back to me.
OK. So don't mess with the part with my pen in it.
Below is a picture of the hole in the metal plate. I have a light shining inside so you can see that it is clear and not blocked at all.
Attachments
PTC orifice hole in plate.jpg

hu5ker555
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hu5ker555

Re: rough idle especially in reverse with wheel turned to the right

Post by hu5ker555 » Sun Feb 16, 2020 5:55 pm

Thanks everyone for the suggestions. Successfully replace the turbo intake hose, got everything reconnected, and we're back in action. Smooth running again. Any questions on how to replace this part, hit me up. It was a challenge, but not impossible.

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