turbo question

ac102nv · Post by **ac102nv** » 17 Jul 2005, 09:18

I just purchased a '02 S60 2.4t with 60,000 miles on it. Runs great with one exception and I'm not sure if it's normal or not, so the advice of knowledgable and experience is what I'm after.
When I'm in the gas more than about 75% or so the engine surges. It feels like the computer or waste gate is allowing way to much pressure loss, then allows to build, then releases, repeat.... Is this normal behavior or should it build to max boost and maintain until you let off the throttle? And ideas or suggestions would be greatly appreciated.

Also, I'm new around here....great website!

Thanks,
Greg

Shea · Post by **Shea** » 17 Jul 2005, 23:22

do you mean you give it gas and it hesitates for like 3 seconds then it sort of lurches forward? if so i have the same problem and i know its not my shifting. last time i changed my oil the jumping problem went away. also try to figure out if the the problem happens from breaking somewhat hard because iv heard from fellow volvo drivers near me that it can "temporarily stop the transmission from kicking in"

Guest · Post by **Guest** » 18 Jul 2005, 10:19

Doesn't seem to be a turbo lag issue. I can be cruising at say 60mph, floor it to pass another car and it takes off like it should, with trans kickdown and all. However after it builds max boost it either releases too much or retards timing or something because then the surging starts and continues until you let off the throttle. I don't know if it's the waste gate or the computer trying to control boost and doing a terrible job of it. Seems to me it should be smooth....but this is my first turbo and only second Volvo.

ac102nv · Post by **ac102nv** » 18 Jul 2005, 10:22

Sorry, last reply was mine...ac102nv...forgot to login.

Guest · Post by **Guest** » 18 Jul 2005, 14:19

sounds like a sick ass boost of speed when your shifting up does the boost pressure gauge (above the gas and oil gauge) fill with a lot of white when it happens?

Shea · Post by **Shea** » 18 Jul 2005, 14:21

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
shit, I also forgot to login haha

ac102nv · Post by **ac102nv** » 18 Jul 2005, 16:24

...sorry, no boost guage on my 2.4t with auto trans. But it certainly builds boost fast...then releases. I want to figure out how to keep the boost going. But I'm afraid to add a chip if something else is already messed up.

Thanks,

ac102nv · Post by **ac102nv** » 20 Jul 2005, 23:25

I was giving it another visual once over tonight and noticed what might be a cause. There's a rubber hose, and 1/2" OD that comes off the intake manifold/plenum and goes down to a sensor or two or three under the manifold. It is split where is attaches and at idle you can hear a leak if you run your finger over it. So I'm thinking it's sending faulty boost info to the computer that's doing who knows what trying to correct. I'll check with the dealer tomorrow on a new hose and clamps....

Post by **matthew1** » 21 Jul 2005, 00:00

Yes, that would make sense. Air entering the system post-measurement (mass airflow sensor), mismatched fuel-air ratio results, engine drastically changes boost or timing to compensate, repeat. Thus, a slow pulsing of power.

Let us know.

ac102nv · Post by **ac102nv** » 23 Jul 2005, 17:33

Fixed the leaking hose last night. Surges seem to be less, but still there. I also replaced spark plugs with OEM's and no difference. What I noticed today though was that during a hard take off heading up hill, there seemed to be no surging. So more load on the engine actually helped. Does that make sense to anyone? This is my first turbo car and needless to say I'm confused. I don't think it's the fuel pump or filter because surges happen throughout RPM range starting as low as 3-4000. Seems to me it has to be timing or boost/waste gate related. But you guys know much more and any ideas would be greatly appreciated.

Thanks,
Greg