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Discussion Starter · #1 · (Edited)
Some background.
2005 Volvo S40 FWD T5 AUTOMATIC

Current Symptoms
1. Car has sporadic boosting from 2-3k RPMs - I do not push the gas hard . Maybe 1/4 down which shouldn't engage BOOST? but it does.
2. If i keep the car shifting before (around) 2k rpms it drives fine.
3. If i let the car "do its thing" it will go in to a "limp mode". No lights on the dash - but the car is VERY VERY slow.

Old Symptoms - Before I found these forums.
1. Code P0122 (i think) Whatever the MAF code is - REPLACED MAF
2. Code for Air Leak AFTER MAF - Checked piping / all OK. Checked Vac Leaks / none found. REPLACED PCV (Was shot!)
3. Spiking / weird boosting under light driving - REPLACED FPS
4. REPLACED TCV


Can Spark plugs cause these symptoms I'm having of the sporadic boosting?

Boost is normal when i "punch it" around 10psi
HNG is normal 18-20 idle
 

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TCV would be my guess as well. Don't see how spark plugs come into play in this case.

Have you looked at your turbo check valve? Some early 2005 still have the old rubber flap style. Replace it if you do. Clean it if you have ball style. Look Here
 

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Discussion Starter · #4 ·
TCV would be my guess as well. Don't see how spark plugs come into play in this case.

Have you looked at your turbo check valve? Some early 2005 still have the old rubber flap style. Replace it if you do. Clean it if you have ball style. Look Here
Yes, isnt that the "PCV" ? It was the "FLAPPER" thing - Totally gone. I put in the check ball valve kind.

Are there directions on changing the TCV ? How hard of a job is it?
What valve is in the airbox?
 

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Nope, PCV is integrated with the oil filter housing. At least we're on the same page now.

Valve in the airbox is the so called "snow valve". It simply opens if you totally clog your intake pipe. Not a factor here.

This Post will help you a bit with the TCV. For your situation I'd just go stock. Do not mess up the vacuum lines. This is so common it's laughable. You have FWD :thumbup: Helpful when doing this job.
 

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Discussion Starter · #8 ·
Thank you - T5CO if you want to PM me the price and when you can ship it? Id obviously want it asap.


When the car goes in to "limp mode" - If i un-hook the MAF then it seems to run "normal" again - Is that "normal" reaction?
 

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If you loose a major component like the MAF the car will ignore it's input & make a best guess. Kind of like the good old days when things were basic without multiple input sensors. It certainly won't let the car make full boost as that would be risky. Overboost is usually the trigger for limp home. So yes, not unexpected.
 

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Discussion Starter · #10 ·
ok
so I got the Boost guage all hooked up last night.
I am idling 20HGN and boosting at 9 or 10 PSI

Since the PSI is normal boost - does that mean my TCV/BCV is OK ?

One other thing i just discovered is my battery is TOAST. It died after like 5 minutes of having the lights on while working on the car.
Charged it overnight - didnt take a charge.

Can a bad / weak battery cause these surging spikes from 2-3k rpm?
 

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Although a bad battery can cause all sorts of weird things to happen in these cars it probably isn't the cause here. If you write tomorrow that all your issues are gone I won't be super surprised though. No worries in any case. You must get a new battery & eventually your TCV will fail. Common items.
 

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Discussion Starter · #12 ·
ok thanks. I think T5CO is going to hook me up with the stock TCV and ill get a new battery after work today! I'll report back

Thank you for the assistance
 

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Discussion Starter · #13 ·
So its not the bAttery.
Im thinking i pulled something loose from the key / ignition ? This non starting issue started after i hooked up the power to my boost guage.

Possible blown fuse?
All the lights work. Locks. Windows etc.

I found some wires running up that arent hooked up to anything. But im pretty sure they are "aftermarket"


 

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Yup, that would be some non-factory stuff there. A little scary, they head right to the ignition switch. Time to do some digging.
 

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Not sure, that green connector looks like the connector for the passenger temp sensor in mine, but I could be wrong. I had an error because for SOME REASON it was disconnected and pushing me a code. I used some MAF cleaner, cleaned up the sensor and reconnected it and the error went away.

Also, most chargers have a short detector that will shut them down if the connections receive the same current they put out on the battery, so you need to take your battery to a local shop and have them hook up a load testor to be sure. bad batteries and cells dying can cause all kinds of voltage spikes and issues including expensive repairs.

So idling you should be at or right below barometer pressure for your area, and boosting up to 12psi stock I believe, so it looks good to me.

Yes that looks like aftermarket repair, unless volvo doesn't replace the entire harness section and did that themselves, I'd rip all those connectors off and redo them all and see if it fixes your non starting problem.
 

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Discussion Starter · #16 ·
yeah the green connector is the sensor for temp. I took it off temporarily to check what it was (get part number)

I pulled on all of the wires making sure they were snug and not loose up there. Maybe I just need to undo all of the connections and try to hook things up normally.

One of the power wires (red in that bundle) is indeed HOT

I tried tapping on the ignition (things ive read)
Tried starting in neutral
Let the car roll back a few feet

This car is pissing me off. Seems i fixed one thing and 10 other issues popped up.
I can deal with the sputtering and crap - but the non starting issue has gotten the best of me.

What fuses should I check that deal with the ignition / position 3 on ignition ?
 

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Discussion Starter · #17 ·
So it seems there may have been a remote start. I disconnected the wiring left behind and hooked up the ignition again. Fired right up. What a relief !

Now, this weekend Ill probably attempt the TCV. Although it seems to be running pretty good? Could a loose ignition wire have caused my initial hesitation issues?
 

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No, probably not. I have a similar weird light throttle and boost spiking issue too - I'm pretty sure the TCV is the culprit. But that's a post-holiday gift to V50.
 

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hmm ok
The part I changed that was hooked to the turbo was



So, this is the TCV ?

You're touching the TCV right here. I expect it's a simple pull hoses off and put them back on situation. Nothing too complicated requiring a write-up.
 
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