850 Slightly erratic boost behaviour from 850R

Hi there

So I have noticed some slightly strange behaviour from my 850R when boosting. I'm only working off the factory boost gauge.. but when throttle is applied it has been boosting up to about 8 or 9/10ths of the scale. Over the last week, over about 4000ish, it seems to drop off slightly. Maybe back to 7/10ths. However, today, I got a chance to do some decent pulls out in the cane fields and there seemed to be no drop off at all. In fact, over about 4500, the boost actually crept up to just over the end of the scale. Now I'm wondering if I imagined the boost fade or whether maybe I was just lifting slightly cos I was being a fraidy cat.

I was thinking the fade may have been due to a worn wastegate actuator. Or simply the 15G running out of puff, but that seems a bit unlikely now I've seen it boosting higher at higher revs. But, would the wastegate actuator problem present intermittently? And could it cause the boost creep that I noticed today.

In the last week I've also replaced the clamp on the pipe to throttle body as I blew it the other week and had started leaking boost slightly since. Also, had the downpipe retightened 2 days ago, following fitment ~1200kms ago. I did think maybe it's just taking the ecu a while to relearn since it's not leaking at charge pipe anymore.

The car went into GLT last week for new radiator, oil change and fluid flush. I've gone from a do88 radiator to an OEM radiator. I did think maybe the OEM radiator could be creating extra heat soak.

The car is currently running 15G, do88 intercooler and RIP kit, BSR tune, 3" dp and high flow cat. Car has ipd TCV and has had a new CBV fitted, as well as all new silicone lines which have been vacuum tested not long ago. Oh and 6month old walbro 255 fitted.

Oh and when I fitted new t bolt clamp, I forget to plug the idle air valve back in and started it up. Idle was up to about 1400rpm. Is that normal? Lambda light came on and hasn't gone out yet. Don't think that would cause issue though?

Lots of variables. And that's sort of what's had me thinking..

Anyone got any ideas?

Comments

  • GhettobirdJulian (@Ghettobird) Melbourne - SE Suburbs
    edited June 12
    Lots and lots of variables
    Check over all of the turbo hoses - CBV wastegate and intake ref hose.
    Check for codes, get a proper boost gauge and work out if its really creeping, or maybe something else is skew.
    IPD TCVs can have mixed results, if you can find an original pierberg valve id chuck that on and see if maybe the TCV is playing up.

    What boost level is the BSR tune supposed to run at?
    Is the wastegate rod adjusted to Volvo spec with a proper tool or just cranked down tight? If it's too tight the turbo will overshoot the desired boost level and result in a visible fluctuation in boost pressure as the ECU throttles TCV duty cycle to compensate.

    The cat and DP wont cause weird boost issues unless the cat has collapsed internally and is blocking flow.

    These ECUs dont relearn anything, they are set in their values and adjustments - bar some vary very minor fuel trims that the car can adapt for very small variances in injector consistency. It should run 100% within a minute of resetting everything

    Check the above hoses, check all pressure hoses, intake/MAF to turbo hose, codes and go from there.
  • Yeah, boost gauge is a bit of a necessity at this point. I've heard the ipd TCV can be a bit funky and I picked it up second hand from a mate so who knows. Still got original item so will give that a go. I bought a Bosch code reader a while back but the bastard wouldn't work. Have heard the 850 systems are a bit finnicky to read cos they are sort of transitionary between OBD1 and OBD2. Can you suggest a code reader that will work?

    Oh and no idea about actuator. Never touched it because it seemed to be working fine. Do they require adjustment over time as they wear? Or set and forget kind of thing?

    The tune is supposed to be set to 1 bar, which i had assumed from reading was right around the end of the white on gauge. The tune is made for a 16T and stock injectors. I have a lovely little Mamba 16T with about 30,000kms to put in the car.

    I'm well aware of what a bad cat will do.. When I bought the car it was only boosting to ~4psi and that's when I replaced plugs, leads, cap and rotor, fuel pump, fuel filter, CBV and TCV and checked over all the vac/boost lines. A mechanic suggested maybe cat was last possible cause. As soon as the cat was replaced it was boosting up to 2/3 gauge again. Which was a a few psi higher than my T5 (which ran stock levels) and had a boost gauge which checked out at about 8psi, which seemed to check out around the 10.8psi mark.

    Surprised the ecu doesn't relearn. Thought they were cleverer then they are.

    Just took it for another little fang and it seems to be slightly laggier. More throttle to start making the boost climb. And maybe peaking a little lower than before. Just funny this diva behaviour seemed to started when I fitted the t bolt clamp. Maybe I'll remove and refit it.

    The joys of fiddling with 850 Turbos.
  • edited June 13
    So I checked out my hoses this morning. All looked and felt good. Refitted the new clamp on charge pipe. Took it for a drive. Driving great. Maybe still slightly low at peak boost but no laggier. Maybe just less willing to stay in gear and let the boost climb at lower throttle inputs. Also more willing to downshift at lower throttle inputs. Wondering if this is maybe related to trans flush. Lambda light still on.

    Then on the way to work this arv, didn't get much opportunity to test it out but as I pulled out of on roundabout, up a slight hill at maybe 1/3rd throttle, it stayed in gear and pulled through to around peak boost, without shifting, like I had become used to with the new tune.

    It *feels* like it should be TCV related. Just because there is an inconsistency there with the behaviour.

    I was doing some reading and it seems by unplugging the TCV and seeing what the car will boost to, I can get rough idea of what the wastegate cracking pressure is set to, so I'll give that a go tomorrow. From memory, an R should be set to about 4.7psi? And see if I can dig out my original boost solenoid on the weekend.

    I tried to find a brand new OEM boot solenoid on ipd, fcp, etc and couldn't find one. Are these nla?

    Also, intrigued by the code reader app for 850s so am going to put an order through for a Bluetooth/wireless adaptor.

    Thanks for any help and advice you can give.
  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    Isn't the ECU in a default setting when it's had the lambda tripped and codes Ned to be reset?
  • edited June 14
    I don't know @Ex850R.. whenever I have tripped lambda in the past (in the R and my old T5) it's been from a blown clamp and once I reconnect, it will usually drive fine and switch off lambda within a few days. Surprised it hasn't this time but it was because of the idle valve this time so yeah, different.

    When you say 'default setting', what do you mean?
  • GhettobirdJulian (@Ghettobird) Melbourne - SE Suburbs
    Pull the terminals off the battery and leave them disconected for a few hours.
    Failing that, you'll need a scanner that will talk to the 850's crap-spec OBD ECU, Most wont.

    It might have a limp mode, it probably wont. Codes, base adjustment and good gauges are the only thing you can rely on
  • Thanks @Ghettobird

    Reset Ecu. Lambda off and I *think* it might be driving differently. Only got a quick drive in at peak hour. But it did seem to break traction a little bit easier than it had been.

    Don't wanna speak too soon but I find it strange that it would go into a 'limp mode' but be only slightly different. Would it just richen up the AFR and slightly drop peak boost a bit or something?

    Oh and one more thing.. I've noticed when the car is shifting whilst boosting over about 10psi, it will make a sound kind of like rattling a spray can or rolling a dice maybe. Hard to describe. Is that likely the CBV?
  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    Initial thought on that sound is pinging or running lean...do you use premium fuel? 95 minimum...
    All this is conjecture and seat of the pants stuff isn't telling you anything. You need afr gauge that logs or getting connected to a computer on a dyno. By all means do a STAGE 0, then go from there, are you using Volvo plugs? Bougicord leads? Standard wear items in ignition all Volvo? Hoses replaced? You must replace all of this as its very old. The only way to diagnose is do stage 0 and go from there.
  • edited June 15
    Yeah, always 98. I had thought pinging but I've heard pinging before, albeit in other kinds of motors and it's a different kind of sound. Also, I only ever hear it during the shift at higher boost levels. And never like just under load driving up hills or when boosting any other time. The exhaust rubs a bit on my rear sway and the downpipe was rubbing a bit when first installed so i did think maybe it is the flex bellows rubbing on the body or something when the engine moves during shifting and making a weird sound.

    Volvo plugs, bougicord leads and bosch rotor and cap. About 17000kms on them. Pretty much everything for stage zero done. I've had head reconditioned. So headgasket obviously done too. Timing belt, tensioner and water pump done too. As I said, all boost lines have been done.
    Fuel pump and filter done. Throttle body cleaned. Did the TCV and CBV. Oh and it has new intercooler and piping. New air filter. New radiator, hoses, expansion tank. New coolant temp sensor and fan relay. Even new throttle cable. There's nothing much old on this car. Trans flushed several times under my ownership. I've put the 17000kms on it in about 7 months encompassing a trip to yeppoon and a trip to yamba. And used the car virtually every day without issue.

    Just took it for a little drive. Didn't even go WOT but didn't need to. Thing is going great again. Much happier to stay in gear and pull through if that is what I ask of it and the shove in the back is back to where it was. Even without really pushing it.

    Oh and i checked average fuel consumption and even though I'd pretty much been babying it the last few days it had jumped from an 11L/100km average (lots of city driving) to about 17L/100km. Reset it and will monitor but am thinking the lambda trip had initiated rich running.

    I still like the idea of getting an AFR rigged up. I've heard AEM is good one. And i will be pulling the autometer boost gauge from my T5 and rigging it up when i get a chance.
  • Spicy says hello!
  • GhettobirdJulian (@Ghettobird) Melbourne - SE Suburbs
    Or maybe its pinging its head off on shifts?
  • Yeah sure, maybe @Ghettobird



    Only one way to see I guess. AFR gauge here I come. Will I have to get another bung fitted to downpipe?

    Is there any reason it would ping whilst shifting in particular?
  • Forgot to mention it has a new Bosch O2 sensor as well.
    Ghettobird
  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    The on block knock/ping sensors do go bad but rare.
    Not cheap!
    Cam position sensor? Worth replacing.
    Not much else to do .
    Do a plug check for lean running, gap check.
    Do compression while there and a leakdown test if you can.
    If it all gets to much I'll give you 50bux for it to rid you of your woe.....
    GhettobirdTL_V70
  • Thanks Snoop
    And Ghettobird

    Lots of helpful thoughts. Was driving well today. Behaving as normal. And lambda hasn't come back on again.

    If there was an issue with knock sensor or cam position sensor would I get a code?

    Plugs worth checking but I wonder if I will see much evidence of lean running if it's only leaning out once in a blue moon during harder shifts.

    50 bucks is tempting.. maybe if you throw in a night out at the cinema with you and Mrs Snoopy, I'll think about it. ;)
  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    Gee, you are a cheap date!
  • Only when I know the libations will get the Volvo mechanical knowledge flowing freely @Ex850R
  • Ex850RSnoopy (@Ex850R) Somewhere Over the Rainbow. Melbourne.
    Only when I know the libations will get the Volvo mechanical knowledge flowing freely @Ex850R

    Haha, I don't drink....
  • Haha, I don't drink....

    Ah well, I'm sure Mrs Snoopy will wet her lips
    timbo
Sign In or Register to comment.