I've been chasing a CEL code for a while now, a P0171.

I used to have an occasional rough idle, but it went away with a vacuum leak repair...but the car pretty much runs normal right now.

I replaced the MAF Sensor about 20K miles ago, same with the Spark Plugs.

I replaced both O2 sensors recently, and have checked and re-checked and re-checked for vacuum leaks (replaced a few elbows which I thought were clearly the issue, as they were split in two). The rest of the vacuum system seems to be fine, but I will check it again tomorrow.

My gas mileage really hasn't suffered any noticeable drop off.

The OBD2 scanner says:

"Intake leak after Mass Air Flow (MAF) Sensor.
Restriction in Fuel System
Spark plugs have excessive wear
Faulty Bank 1 Sensor 1 Oxygen sensor"

It's not saying those are ALL wrong, I think it's the generic "these are the common issues".
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone

I checked my plugs, they were all gapped off. As I understand it, .028 is preferred for the GLT's, and mine were (at best) .033 with 2 of them being .035.

But that's all moot right now, as during the removal process, one of them decided to fly across my garage and break in two on the ground.

D'oh!
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone

After cleaning the air hose (or whatever it's called) and the PCT (I think that's the name) and replaced hoses, I drove it for about 50 miles before the CEL came on. Same code.

Going co check it again later today, when I'm done with all the Christmas stuff today.
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone

My 1995 doesn't have this white vacuum line. Does it go somewhere forward of the air cleaner or towards the throttle body?



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Keeping it running is better than buying new

After closer inspection of the picture, the white line attaches to a hard pipe. You can see it directly at the bottom of the white vacuum line, about 1/4 inch from the black connector and just above the water pipe.
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Keeping it running is better than buying new

I think the issue might be related to the Fuel Pressure regulator, and the hoses involved with that.

The elbow that is connected to the accordion hose (off the air filter) seems suspect, and the rubber coupler between the hard plastic hose and the metal line that goes TO the FPR, is shot (I replaced it months ago, but I suspect that my repair wasn't as air tight as I thought).

The elbow at t-pipe was replaced with the PCV 2 years ago, so I dont that elbow is suspect.

I will hopefully get this squared away tomorrow, and will update (as long as I don't try to blow up the car out of frustration...only joking. Somewhat)
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone

I suspect you still have a vacuum leak. Check the hose leaving the air cleaner, the accordion hose can develop cracks which are hard to see. If you have a turbo, check all of the clamps along the intercooler piping (just try to twist them by hand, if there is movement tighten the clamps).

The vacuum lines can leak anywhere, not just the elbows. The worst offender is the hidden one by cyl #1. If you have a vacuum gauge, plug it into one of the extra titts on the vacuum tree, you should get about 15-17psi during deceleration. That number is a guess on my part!

A glove test may not work correctly given the age as the valve stem seals may be worn a lot. But then there should be smoke from the exhaust on long downhill no throttle runs.
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Keeping it running is better than buying new

I had replaced all of the vacuum hosing off of the MAF, and replaced the accordion hose when I bought the car.

But I was wondering if the length of the hoses matter? I gave myself ample hose length.

I do know of one hoses that goes from under the accordion hose, towards the firewall (and it meets up with a metal hose). the connection between that hose and the metal hose is shot and I jerry-rigged a connection. But I'm not sure if that's the issue, since it is still connected.
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone

Replacement hoses can be longer without a problem.

If you can twist that vacuum hose on the metal fitting easily, it will leak. Is this a turbo? Then check all of the hoses from the boost control. IPD sells a colored silicone hose set, which is a royal pain to install but looks nice. There is also a long 24inch? vacuum line from the front of the intake manifold back to the turbo boost.

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Keeping it running is better than buying new

Yeah, it's a GLT.

Do you know the part to replace that? I can't find out what the damn part is called. Hopefully that would be the issue.

I had bought the IPD hoses already, that's what I've been using.
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone.

Do you mean the waste gate? That is a non failing part. The yellow line should have a clamp that gives a nice snug fit.

You could also try spraying TB cleaner, starter fluid, butane, or some other flammable around suspect parts like the injector seals, the intake manifold gasket, etc and see if the idle changes.
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Keeping it running is better than buying new

Found I think some pictures, but I can't seem to upload them via my phone.

I think I've emailed you before, I'll try sending them that way
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone

It's from the bottom of the accordion thing, and it's a hard plastic tube that connects to a metal tube.

I wish I could describe it better, I don't think I have a picture handy
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1985 245. 246K Gone..but not forgotten. Sold in 2013, found 2018! Still running on the road. Of course. 1993 Volvo 850 soon to be gone