this post was submitted on 12 Apr 2025
9 points (100.0% liked)

Mechanic Advice

345 readers
11 users here now

This community is for getting help with vehicle or other mechanical problems.

Remember, there are no stupid questions, we want everyone to feel welcome. If you don't want to answer a question that you think is silly, then just move on and keep it to yourself.

Rules:

  1. Don't be a dick

That is all.

founded 2 years ago
MODERATORS
 

Car was running fine, parked for a week or so and now dies immediately after start (doesn't stop like it's low on fuel, stops like if I were to turn the ignition to off). No amount of throttle changes this behavior. I did some Internet research and found that disconnecting the MAF sensor might lead me to the cause if it runs after disconnect. Exact same behavior when disconnected. While in the engine bay I found that if I disconnected the Boost Pressure Solenoid, it started up and ran (idle was a little high, but seems to run okay). The fact it's running when that solenoid is disconnected leads me to believe it's not (at least entirely) a fuel delivery issue. Would you expect that the solenoid itself is the issue, or does that lead you to expect it's some other issue.

Some background history that MIGHT be helpful. Radiator cracked sometime last year (saw low coolant light and stopped before engine got hot), finally got it replaced in Jan or Feb. Took for a test drive and was running fine, then stalled on us right as we left the neighborhood. (Threw a fuel delivery code, but only once, and I didn't take a pic. Didn't show in history or active codes) Would not start. If it did start, would die shortly after (felt and seemed like fuel delivery issues, with a sputter stop). Let it sit a few minutes, and then was able to drive it home without issue. Have since driven it far and at freeway speeds without issues.

Car shows 2 engine codes, will provide images in comments.

P0140 P0141

Stored codes P0036 P0140 P0141

None of these are NEW codes, it was running "fine" with them.

top 14 comments
sorted by: hot top controversial new old
[–] [email protected] 4 points 9 hours ago (2 children)

I haven't looked at a diagram for that car, so my thoughts will be generic.

Let's start with the codes. I'll run a non-boosted engine with O2 codes, because the worst it'll do is maybe run a little rich. With a turbo car, you're playing with fire (depending on the system design). It should default to limp mode, but extra fuel in a turbo engine can be a bad thing as detonation is even more likely (though lean is far worse).

Without perusing the diagrams for that engine, pI suspect disconnecting that solenoid somehow forces the computer to use a default mix setting.

Do we know if that solenoid is really a solenoid, or actually a sensor (manufacturers sometimes use those terms interchangeably). Or does the computer sense the current demand or position of that solenoid?

[–] [email protected] 3 points 9 hours ago (1 children)
[–] [email protected] 2 points 4 hours ago* (last edited 4 hours ago) (1 children)

Interesting, a vacuum solenoid.

I'd guess it's defective if removing it resolves issues. When you remove it, do you cap the lines?

Places like autozone should have a vacuum pump to test it. It's probably a simple switch that closes or opens with vacuum.

[–] [email protected] 1 points 3 hours ago

By disconnect, all I did was unplug the electric, left the component in place.

[–] [email protected] 2 points 9 hours ago (1 children)

Also, looked under my car and I can see (and barely reach) some severed wires that run along the exhaust right around 1/3 back from the front of the car. I'm reasonably certain that's supposed to go to my 02 sensor, which would explain the code.

[–] [email protected] 2 points 4 hours ago

Doh! Sure would.

Shouldn't be too hard to replace, make sure to find a really good insulator replacement (just in case) and wire tie them to the body away from the exhaust.

[–] [email protected] 4 points 9 hours ago (1 children)

Any problems with accelerating?

I'm not very familiar with Volvos or boost systems. Check the hoses coming from the boost solenoid for damage. It could be a massive vacuum leak causing it to shut off the moment the boost solenoid opens. The boost solenoid may not be opening when unplugged which is why the car runs.

[–] [email protected] 3 points 9 hours ago (1 children)

Ooo good question. I didn't want to drive it while it was unplugged because I'm honestly not sure what it does. (I understand it controls the airflow to the waste gate, but beyond providing more air for combustion, I don't know much about turbos)

Before this, I didn't have any issues accelerating. I could feel the turbo kick in when I ask for some umph.

[–] [email protected] 3 points 9 hours ago (1 children)

Hopefully it's just a damaged hose! That's where I'd start. Where I am mice are a problem and anything that sits ends up chewed on lol

[–] [email protected] 3 points 9 hours ago* (last edited 9 hours ago) (1 children)

I checked what I could trace from the hoses. The one yellow marked one, and the blue one I can see and follow to where they terminate, and I didn't see or feel any significant issues.

The lowest yellow hose

(the one under my thumb) I can't follow, but a few small tugs, and I'm reasonably certain it's connected at the end as well.

[–] [email protected] 1 points 8 hours ago (1 children)
[–] [email protected] 1 points 7 hours ago (1 children)

In your experience, would simply having a couple pin holes or small tears be enough to cause what I'm seeing? At least one of the hoses felt really rough on the outside, I would not be surprised if it wasn't totally intact.

[–] [email protected] 1 points 6 hours ago

No small holes would cause it to run rough and accelerate poorly I would think. Though with your O2 sensors not working the computer won't be able to compensate for any vacuum leaks.

[–] [email protected] 2 points 10 hours ago