jschaefer7406 Posted October 31, 2008 Report Share Posted October 31, 2008 Hello everyone,Have a 2000 S70 AWD, LPT of course. For a little background, I have a brand new CBV diaphram, new OEM TCV, and new silicone lines to TCV. Car is in excellent mechanical condition, 121k miles. My concern is, under sudden part-throttle acceleration with low load (you know, like if you punch it just a little on a highway straight stretch ), the boost is sometimes erratic. It'll go to 5, then bounce down to 2 or so, then back up. No noticable rhythm to it. Boost also fades under the same conditions. If I accelerate real hard, it'll go to 6 psi and stay there (no fading or other strangeness, but I know 6 is a little low for an LPT). I am thinking of upgrading to Stylin intercooler hoses, but I don't know if this is related or not. I tried the IPD TCV, but got the same erratic readings with it (had two of them), so I opted for a fresh (but OEM) valve. Wastegate actuator is set to 3 psi. I don't know what else to check. Anyone else have these symptoms? Is this normal with an ETS car?Thanks in advance,Joe Link to comment Share on other sites More sharing options...
turbobrick Posted October 31, 2008 Report Share Posted October 31, 2008 oxygen sensor. Link to comment Share on other sites More sharing options...
jschaefer7406 Posted November 1, 2008 Author Report Share Posted November 1, 2008 oxygen sensor.Hello,Thanks for the reply. I have no DTC's for the O2 sensor, so I assume it's okay. Not doubting you though. Why would this occur only under moderate boost and not under full pressure?Thanks,Joe Link to comment Share on other sites More sharing options...
turbobrick Posted November 2, 2008 Report Share Posted November 2, 2008 i had a similar condition, and this is how i fixed it.basically your car's ecu has two modes.. open loop and closed loop.under open loop it calculates AFR's on the fly by using the readings from your oxygen sensor, once you lay the hammer down so to speak your ECU enters closed loop.closed loop means the car is operating off a set of predefined parameters hardcoded into your ECU, hence why things appear to be normal when you're giving her full throttle.its just a guess though, so i'd advise a second opinion before throwing down 100 bucks to fix a problem that may not necessarily need fixing. Link to comment Share on other sites More sharing options...
sconeman Posted November 3, 2008 Report Share Posted November 3, 2008 i had a similar condition, and this is how i fixed it.basically your car's ecu has two modes.. open loop and closed loop.under open loop it calculates AFR's on the fly by using the readings from your oxygen sensor, once you lay the hammer down so to speak your ECU enters closed loop.closed loop means the car is operating off a set of predefined parameters hardcoded into your ECU, hence why things appear to be normal when you're giving her full throttle.its just a guess though, so i'd advise a second opinion before throwing down 100 bucks to fix a problem that may not necessarily need fixing.right and it can take a while for the ECM to throw a code on something like this Link to comment Share on other sites More sharing options...
JA VOLVO Posted November 7, 2008 Report Share Posted November 7, 2008 How often should you replace the O2 sensors? I have had this issue off and on. Seems to depend a lot on the temp of the day. Worse when hot, better when cold. Link to comment Share on other sites More sharing options...
jschaefer7406 Posted November 10, 2008 Author Report Share Posted November 10, 2008 How often should you replace the O2 sensors? I have had this issue off and on. Seems to depend a lot on the temp of the day. Worse when hot, better when cold.Aaah, so I'm not the only one with this issue....Joe Link to comment Share on other sites More sharing options...
randomdude Posted November 10, 2008 Report Share Posted November 10, 2008 i have no for sure answer but id say at least 50.000 miles. especially if youve been running very rich or burning some oil because the deposits will cause the sensor to not be able to read properly. Link to comment Share on other sites More sharing options...
JA VOLVO Posted November 12, 2008 Report Share Posted November 12, 2008 i have no for sure answer but id say at least 50.000 miles. especially if youve been running very rich or burning some oil because the deposits will cause the sensor to not be able to read properly.I have about 115K on the clock and I have no idea if they have ever been replaced. I am not burning anything or running rich that I know of.Might be a good idea to replace, but they do cost a bit. Link to comment Share on other sites More sharing options...
randomdude Posted November 12, 2008 Report Share Posted November 12, 2008 not if you buy the $30 universal bosch and solder and shrink wrap them into the stock harness. Link to comment Share on other sites More sharing options...
Seagrams Posted November 12, 2008 Report Share Posted November 12, 2008 just a thought, but have you double checked how you hooked the lines up to the TCV? not trying to question your abilities, but it's really easy to get the lines switched (i did it once, i'm sure others have too) and it caused erratic boost and low boost like you're describing... I was positive i had them hooked up right (red to red yellow to yellow not rocket science) but was under the hood one day and realized i must have had a dyslexic moment because i had the two signal lines on backwards. That's what I would check first, after all it's free and i wouldn't think on an 8 year old car it would be your O2 sensors (unless you've been screwing around with your afrs or running too much boost with an MBC or something). I'd say the same thing for the intercooler hoses, and silicon isn't really necessary for 6 or 8 psi.And as far as the car boosting differently depending on the outside air temp i'd imagine that's just a matter of colder air providing better performance esp with turbocharged engines, the colder the air going in to the turbo and the colder the air flowing through the intercooler the better. Link to comment Share on other sites More sharing options...
jschaefer7406 Posted November 13, 2008 Author Report Share Posted November 13, 2008 Hello,Thanks for the reply. I used to work at a Volvo dealer as a Master technician, but never got into boost gauges or anything aftermarket. With that in mind, I'm not sure what is normal on one of these LPT ME7 cars. I have checked the TCV lines, but it couldn't hurt to double check . As far as the other items, I agree with you. I would't think the hoses or O2's would be faulty at this mileage. I had an '88 760 Turbo with 283k miles on it before this car. It had the original 02 sensor and intercooler hoses. Now, granted, this car is a lot more complex. I don't doubt these items do fail. However, these ECM's are so touchy that I would think an MIL would set for a boost leak or 02 sensor problem (for example, I have seen O2 sensors on these cars fail at fewer miles; they always set the MIL though). I could be wrong though, as I have never done any modifying to these cars in my days at the dealpership. Therefore, I appreciate all suggestions and I'm not arguing with any of them. Anyway, thanks for the insight. I do wish I could resolve this...Thanks,Joe Link to comment Share on other sites More sharing options...
randomdude Posted November 13, 2008 Report Share Posted November 13, 2008 i would put money on the O2 being near failed at this many miles. not trying to argue, just saying. Link to comment Share on other sites More sharing options...
Seagrams Posted November 13, 2008 Report Share Posted November 13, 2008 i got 148k, boost like a "raped ape" to use "lookforjoe's" terminology, with tune and on a 96 850R and got original O2 sensors. If they were shot, you'd be throwing DTC's in such short order, your check engine light would look like a christmas tree..... just my .02 but like you said, these cars can be touchy, and in my somewhat limited experience sometimes the solution you overlook because it's too obvious is the first place you should look when you start running out of answers ;) Link to comment Share on other sites More sharing options...
jschaefer7406 Posted November 13, 2008 Author Report Share Posted November 13, 2008 i would put money on the O2 being near failed at this many miles. not trying to argue, just saying.Hello,By all means, any feedback is appreciated and taken into consideration . As I said, also not trying to argue, my experience with these cars at the dealership showed these ECM's to be very sensitive to any incorrect function of sensors (especially the O2's). That's why I assume they're okay. Yeah, I know what happens when you assume . If the upstream O2 sensor is reporting properly to the ECM, why would it cause this erratic boost? And if it isn't reading within spec, why is there no DTC for it? Again, you may be 100% right, so don't think I'm arguing with you. It's just not like anything I've ever seen in my experience.Thanks,Joe Link to comment Share on other sites More sharing options...
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