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Discussion Starter · #1 ·
Hello,

My car has 153k miles. I've had it for a little over a year and it's been pretty reliable but recently I've been having some more concerning issues.

The main issue that worries me is after I leave it idle for a few minutes, it seems to stumble with the rpms bouncing and wanting to stall. It actually has stalled a few times after trying to drive after idle. Sometimes this symptom with cause the check engine light to come on, sometimes not.

I've attached a few codes I've grabbed from my cheap Bluetooth reader. I'm contemplating investing in a vida/dice setup to diagnose further.

From my research I've found a couple possible solutions.

Fuel pressure sensor? I've monitored the readings through the obd(which is less than ideal), it seems to fluctuate between 42-45psi. I do not have a pressure gauge to attach to the rail.

Fuel pump check valve? I don't really have cold start issues. I also can't check if the rail holds pressure when the car is off.

Fuel pump? I think my readings are right for my year, But not positive. Also I don't know if I trust the reading over obd, and it might not capture when or if the pressure freaks out.

Fuel filter? I replaced it last year when I got the car. I don't think it would be clogged again.

PEM? I don't really know how to diagnose problems around that control module. My car is a 2007, so I'm assuming it's been relocated under the seat like previous years? I'm not really fully informed about that situation.

Any advice, corrections to my assumptions, or further diagnostic tips would be appreciated.

Thanks everyone in advance! I've just joined the forums last month and learned so much. I've come to appreciate the car more and can't wait to get my car to stage 0.


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Looks like you've cleared the codes and rechecked them at various times. Looks like a fuel mixture issue, possibly a vacuum leak or fuel pressure. Too much unmetered air or too little fuel makes the system want to richen the fuel mixture. Hence, the rich codes.

What about PCV service and throttle body cleaning? I had some erratic idle and strange codes until I did that.

Also, look at the short term and long term fuel trims. Short term should be around zero. Large positive or negative values tell us something. Check at idle and around 2500 RPMs. Could have a vacuum leak somewhere.

Often one or two problems can cause a cascade of faults. Those are usually electrical issues. Getting to that root cause can be a pain.

If you have a junkyard nearby, you can try a used fuel pressure sensor, to see if that makes a difference. I don't know what years are compatible with 07.
 

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Discussion Starter · #3 ·
Looks like you've cleared the codes and rechecked them at various times. Looks like a fuel mixture issue, possibly a vacuum leak or fuel pressure. Too much unmetered air or too little fuel makes the system want to richen the fuel mixture. Hence, the rich codes.

What about PCV service and throttle body cleaning? I had some erratic idle and strange codes until I did that.

Also, look at the short term and long term fuel trims. Short term should be around zero. Large positive or negative values tell us something. Check at idle and around 2500 RPMs. Could have a vacuum leak somewhere.

Often one or two problems can cause a cascade of faults. Those are usually electrical issues. Getting to that root cause can be a pain.

If you have a junkyard nearby, you can try a used fuel pressure sensor, to see if that makes a difference. I don't know what years are compatible with 07.
Thanks for your reply. I have not cleaned the throttle body or done a pcv service. When I first got the car I checked the pcv the only way I knew how, by checking for air forced out the dipstick tube. Seemed okay to me.

I'll look into doing another evaluation of the pcv and throttle body. I'll also look into the fuel trim numbers.

Thanks for the info!

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Discussion Starter · #4 ·
Fuel trim readings after a 10 minute drive, then sitting idle. Let me know what you think.

Thanks!


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Another way to check PCV condition is placing a rubber glove over the oil filler neck and see if it inflates. Inflation means positive crank pressure and time to service the PCV system...

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Discussion Starter · #6 ·
Another way to check PCV condition is placing a rubber glove over the oil filler neck and see if it inflates. Inflation means positive crank pressure and time to service the PCV system...

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Thanks! I did read about that method on this forum...
http://www.volvoxc.com/forums/showthread.php?28213-PCV-system-mythes-and-testing

I'll have to find some time and run some of these tests. Or just preemptively replace the whole system...


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The negative LTFTs indicate that the engine is running rich. LTFT + STFT greater than 25 or less than -25, will trigger a CEL. So, your right on the edge.

Running rich means the engine is getting too much fuel and the ECM is trying to reduce the amount of fuel. So, a vacuum leak is unlikely. High fuel pressure could do it. You'd need a mechanical fuel gauge to verify as the OBD just reads the sensor.
 

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Discussion Starter · #8 ·
The negative LTFTs indicate that the engine is running rich. LTFT + STFT greater than 25 or less than -25, will trigger a CEL. So, your right on the edge.

Running rich means the engine is getting too much fuel and the ECM is trying to reduce the amount of fuel. So, a vacuum leak is unlikely. High fuel pressure could do it. You'd need a mechanical fuel gauge to verify as the OBD just reads the sensor.
So what about positive STFT while driving? Seems like this overshoot is caused when engine braking down a hill or just letting off the gas.

Any recommendations for mechanical fuel pressure gauge kits that have the Volvo fitting?

Thanks


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STFT will vary as you drive. Under a steady state condition, you'd expect it to be plus/minus 5%.
 

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Just a guess.. you may have more than one issue. The FPS does goes bad and it's not expensive, may even try a used one (be sure to get the right number). It may cause stall/driving issues. You should have about 57psi for the turbo engine

Not really a way to test the PEM.. if located inside the car, it's usually at the right of the spare tire, fixed with velcro. If it's there and looks clean, don't think it's the issue

May want to look at the spark plugs and have a Bosch ignition coil for spare, just in case

Give the PCV a test https://www.youtube.com/watch?v=gK8kUQxhT_8

The fuel pumps are long lasting on Volvo (if it's the original one)
 

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Discussion Starter · #12 ·
Just a guess.. you may have more than one issue. The FPS does goes bad and it's not expensive, may even try a used one (be sure to get the right number). It may cause stall/driving issues. You should have about 57psi for the turbo engine

Not really a way to test the PEM.. if located inside the car, it's usually at the right of the spare tire, fixed with velcro. If it's there and looks clean, don't think it's the issue

May want to look at the spark plugs and have a Bosch ignition coil for spare, just in case

Give the PCV a test https://www.youtube.com/watch?v=gK8kUQxhT_8

The fuel pumps are long lasting on Volvo (if it's the original one)
Thanks for your reply.

I would like to get a mechanical fuel rail gauge to verify fuel pressure sensor operation before I spend 50 bucks on a new sensor. It's also just a good tool to have in the garage as well. It would help diagnose other fuel system issues if the sensor isn't the issue.

You say my fuel pressure should be around 57 psi? I've been trying to find that number but couldn't find a definitive answer. I've seen 42 - 60psi for people saying it's valid.

The obd reading is saying the sensor is seeing about 44psi. So maybe if I'm supposed to get 57 psi and the sensor is under reading at 44, then the PEM is pushing high pressure to the rail, causing it to run rich?

I have a new set of spark plugs, so I have that option. Was going to change them after I fix the running rich issue.

And the PEM I will have to check. I know I saw a module in the trunk that had some corrosion on the wires now that I think about it. Not sure if that was the PEM though.

Let me know your thoughts, thanks.


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Do you have a pick-n-pull type junkyard near you? If so, you could grab a used sensor to try. Just make sure it's compatible with your 07.
 

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Discussion Starter · #14 ·
Do you have a pick-n-pull type junkyard near you? If so, you could grab a used sensor to try. Just make sure it's compatible with your 07.
Nothing close enough to make the drive for one part worth it (or that I have time for). I'm going to contact a few wreckers that pull parts for you that are near me. Or maybe I'll bite the $55 bullet so I know I don't get a faulty sensor.

Thanks for the reply.

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Discussion Starter · #15 ·
Not really a way to test the PEM.. if located inside the car, it's usually at the right of the spare tire, fixed with velcro. If it's there and looks clean, don't think it's the issue
Checked it out... Its there. Harness to it looks in good shape also. The corroded module I recalled was down next to the battery. That's still there too, not looking too healthy lol. Anyone want to tell me quick what that module is?

Also in other news, Im gonna grab a couple used fuel sensors to try out from my buddy. It appears that all s60s from 01-09 use the same sensor? Please correct me if I'm wrong.

Thanks everyone

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Discussion Starter · #16 ·
Update on the issue. Finally got around to testing a couple things.
Tested the fuel pressure at the rail with a gauge.
Saw nearly 80psi for the first 10 seconds after start up. It slowly dropped to about 60 psi once the idle came down. The entire time the needle is bouncing really fast about +/- 3psi.

Swapped in a different fuel sensor (used). Got around 60 psi at start and came down to about 46 psi idle. Also the bouncy needle was now steady(at first I thought it was a low quality gauge).

I cleared my codes and will report back if the issue comes back. But the initial guess is the fuel sensor fixed the issue.

Here are my updated fuel trims, which also look better imo.

Also, does anyone know if anything else could have been damaged while running rich for a few months? I want to make sure I take this repair full circle.

Thanks everyone for your advice. Couldn't have done it without you guys.


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