14 replies to this topic

[b52murph]

Hi All - A few weeks' back, my turbo quit pulling as strongly as usual (maybe only 2-3 psi boost). A few times now, on longer (30min+) drives, it's thrown a P0171 (bank 1 too lean) code. Compounding this, the code isn't there all the time (today, after shutting the car off for an hour the code went away), and normally I'm not getting any codes in city driving.

Quick search here seems to lead to a MAF, however, the MAF was already replaced only 43K mi/5 yrs ago. Could the MAF be on it's way out again this soon (was a factory replacement in Dec 04)? If not the MAF, any other suspects to check before I drop the change on a new MAF?

thx!

[mrbrightside2009]

b52murph, on 14 November 2009 - 11:44 PM, said:

Hi All - A few weeks' back, my turbo quit pulling as strongly as usual (maybe only 2-3 psi boost). A few times now, on longer (30min+) drives, it's thrown a P0171 (bank 1 too lean) code. Compounding this, the code isn't there all the time (today, after shutting the car off for an hour the code went away), and normally I'm not getting any codes in city driving.

Quick search here seems to lead to a MAF, however, the MAF was already replaced only 43K mi/5 yrs ago. Could the MAF be on it's way out again this soon (was a factory replacement in Dec 04)? If not the MAF, any other suspects to check before I drop the change on a new MAF?

thx!

you could try cleaning the maf, also could relate to a vacuum leak, may want to check the elbow on the side of the intake manifold, that's usually with a p0172 code though.

[MrWinkey]

I'm surprised the search didn't turn up the vacuum elbow as many times as it's been covered especially by me?
Check your intake elbow as stated then MAF

[b52murph]

Thanks. Yeah, vacuum tree is tight without leaks. I did take the MAF off and squirted some silicone cleaner in there. If it doesn't do the trick, may just spend the $118 tommorrow on a remanf. MAF @ AutoZone. Worse comes to worse, I'll just return the new MAF if it doesn't fix the problem.

Let me know if it could be anything else. Low boost seems really like an odd result...

BTW. Car is a `96 855T, 183K.

[b52murph]

Well...I tinkered with the car a bit yesterday, disconnecting/reconnecting the MAF, getting & clearing the codes, and hooking up a real boost gauge to see where the psi was. The codes haven't come back in normal driving, but--for certain--I'm only getting 2-3 psi boost maximum. So question is--can you have a failing or bad MAF without having it throw a code, such that the boost limiter is still stuck on?

If not, any other ideas as to why I'm getting such limited boost? All vac & boost hoses are tight and connected properly (checked that before), no CEL.

thanks

[Jaxx]

http://volvospeed.co...e-"boost-leak"/

check your turbo wastegate, make sure it's sealing properly.

If it's fine, unplug your wastegate actuator's vac line and take it easy, just see if you can boost more than 2-3psi. If you can't, then you should look at wastegate preload and then intercooler hoses.

[Fudge_Brownie]

You seem to be quite focused on the MAF and I'm not sure why. See Winkey's post about the vacuum elbow. This sounds more like a vacuum leak. There is more to checking the vacuum system than just checking the tree alone.

Are you running all original rubber vacuum lines? Original intercooler hoses? Try and trace all vacuum lines around the engine bay. Follow the one coming off the turbo wastegate and go from there. And note that the elbow Winkey referenced is part of the PCV system, not the turbo system. There is a picture somewhere around here (Bay13?) of where it is located.

[FCP Groton]

I agree with the above. I doubt it is your MAF, more then likely either a bad waste gate or a vacuum leak.

[b52murph]

FCP Groton, on 17 November 2009 - 12:42 AM, said:

I agree with the above. I doubt it is your MAF, more then likely either a bad waste gate or a vacuum leak.

Thanks much for the wastegate tips--on my way home from work today, I disconnected the vacuum line to the wastegate; no boost pressure difference whatsoever! (idle's @ -15 to -17, boosts to +3-4). Dark now, so going to check for that gap tommorrow. Interstingly, I've had odd trouble with this wategate since I've owned the car; seemed to fix it a couple years' ago by tightening the wategate down, now only to have the problem return and be more pronounced. FWIW...when I connect a hose to the wastegate and blow in it(just lung pressure), the lever does push outward.

Vacuum elbow on the intake side is tight; replaced all the vacuum hoses 4-5 years ago; they're still good.

[b52murph]

Well..checked the wastegate gap--none present, there is a rubber gasket on the lever. All seems to be gap free, however. Pounded on it a bit for good measure, no difference. Boost is still limited to 3-4 psi regardless of whether or not the wastegate actuator vacuum line is connected to the TCV on the side of the airbox. Putting air pressure on the actuator lever causes it to push out (correct action?)

Is is possible for a code to limit boost without throwing a CEL? No codes for a while now detectable by the OBDII scanner. Kind of sounds like I may be having the same problem at Autotechnica in:http://volvospeed.com/vs_forum/index.php/topic/30669-for-those-with-the-elusive-%26quot%3Bboost-leak%26quot%3B/. However, my OBDII scanner doesn't have a "reset the computer" option...just clear codes...

Can a turbo just lose ability to boost with age without actually failing? (didn't think so...but...)

thanks....

[Korruption]

b52murph, on 18 November 2009 - 05:21 AM, said:

Well..checked the wastegate gap--none present, there is a rubber gasket on the lever. All seems to be gap free, however. Pounded on it a bit for good measure, no difference. Boost is still limited to 3-4 psi regardless of whether or not the wastegate actuator vacuum line is connected to the TCV on the side of the airbox. Putting air pressure on the actuator lever causes it to push out (correct action?)

Is is possible for a code to limit boost without throwing a CEL? No codes for a while now detectable by the OBDII scanner. Kind of sounds like I may be having the same problem at Autotechnica in:http://volvospeed.com/vs_forum/index.php/topic/30669-for-those-with-the-elusive-%26quot%3Bboost-leak%26quot%3B/. However, my OBDII scanner doesn't have a "reset the computer" option...just clear codes...

Can a turbo just lose ability to boost with age without actually failing? (didn't think so...but...)

thanks....

Well... if I've learned anything about these cars... it's that anything is possible!!

However, I am with many that have previously stated you're experiencing a (probably severe) boost/vacuum leak.

One other thing to consider is that the stock intercooler soft pipe sections can fail in a different manner. Check to see if they collapse. It could be choking your air supply. Just a thought.

Your car's behavior sounds like my XC when it ripped the underside of the rubber intercooler joint at the throttle body itself.

Good luck!!

[b52murph]

Korruption, on 18 November 2009 - 05:42 AM, said:

Well... if I've learned anything about these cars... it's that anything is possible!!

However, I am with many that have previously stated you're experiencing a (probably severe) boost/vacuum leak.

One other thing to consider is that the stock intercooler soft pipe sections can fail in a different manner. Check to see if they collapse. It could be choking your air supply. Just a thought.

Your car's behavior sounds like my XC when it ripped the underside of the rubber intercooler joint at the throttle body itself.

Good luck!!

Well...thanks much for the tip! That's exactly what happened to mine--a couple of the pieces of soft pipe compressed a little bit when I added some throttle. Took a hard feel at the underside of the throttle body joint and, sure enough, huge tear. This piece was also completely rotted with deposits on the inside. Additionally, a careful inspection found a few other holes in that same piece which (I think) had been there for a long time (maybe even as long as I'd owned the car, 5 years). Ordered all new hoses from IPD (figured I should replace them all) for around $80. Meantime, duct taped the tears; not perfect but am boosting much better than I ever have before--solid 10psi with jumps over that.

Can't wait until the new hoses get here. Thanks much for the assist!

[clarkerussell]

b52murph, on 19 November 2009 - 01:14 AM, said:

Well...thanks much for the tip! That's exactly what happened to mine--a couple of the pieces of soft pipe compressed a little bit when I added some throttle. Took a hard feel at the underside of the throttle body joint and, sure enough, huge tear. This piece was also completely rotted with deposits on the inside. Additionally, a careful inspection found a few other holes in that same piece which (I think) had been there for a long time (maybe even as long as I'd owned the car, 5 years). Ordered all new hoses from IPD (figured I should replace them all) for around $80. Meantime, duct taped the tears; not perfect but am boosting much better than I ever have before--solid 10psi with jumps over that.

Can't wait until the new hoses get here. Thanks much for the assist!

Wow... I'm having similar problems with my s70... p0171 code comes and goes, low boost (measured by seat of the pants), etc. I'll take a look at it tomorrow. What is the best way to measure the actual boost on the turbo?

[b52murph]

clarkerussell, on 19 November 2009 - 01:46 AM, said:

Wow... I'm having similar problems with my s70... p0171 code comes and goes, low boost (measured by seat of the pants), etc. I'll take a look at it tomorrow. What is the best way to measure the actual boost on the turbo?

I'm guessing the `98 S70s are setup same as the 850s (somebody correct me if I'm wrong)--suspect the `99+ -70s are different. Near the throttle body is a black plastic vacuum tree. Mine has the no-numbers boost gauge attached to it, so while I had the gauge in the dash, it didn't tell me anything. Purchased a boost pressure gauge from AutoZone and connected it to an empty port on the tree; ran the line inside the car while I was driving.

Am now boosting an average of 10-12 psi; before I couldn't boost over 3psi.

[MrWinkey]

Sigh again
Drop the wastegate control hose off the BCS and go for a drive...if the pig spools up like a drunken sailor in a Hong Kong port then the mechanical end of the turbo is fine. If it's still a stone then you have a fault on the electricial side.... IN most cases ...The 1171 is a result of your positive pressure spittin' out the end of the intake causing the fuel trim to go haywire as the ECM sees it.
Does that make sense?