'95 850 Turbo Surge

Our '95 has developed a surge under acceleration especially from a standing
start, and actually you can tell it is there about any time you accelerate
fairly hard.

Probably goin to run this thing in to the Volvo folk, but would like some
idea what might be goin on here from anyone that has experienced this
action?? Worry is that so many "repair" outfits have become simple parts
changers until they hit on the right one.

TIA

Jim

 

What kind of "surge"? My 97 850GLT choked and stumbled when
passing for a while. I believe the check-engine light had come on
also. Replacing an oxygen sensor (front, as I recall) cured it.

 

Almost like you are slowly in and out of the throttle. Don't think it is an
02 sensor, gas mileage hasn't changed and the Volvo "specialist" I just had
look at it couldn't get any codes to spit out? Strange that at WOT the thing
runs fine, just kinda hard to be doing 140 or 150mph around town.

Had a similar problem with a Ford Probe but their diagnostic at least spit
out a couple codes and indicated a problem with one of three items. I picked
the least expensive and it turned out to be the right one - MAF sensor (mass
air flow). Guess I'm forced back to the dealer outfit - at least he might
have a few parts to try out??

Jim - Old enough to miss the days when a car ran on gas, fire, and air and
chances were good that when the thing wasn't running right it was only one
or more of those three characters at fault

 

You have a different problem. Mine choked worst at wide open throttle.

 

Have anoither look at the o2 sensor switching rate.- yes with a multimeter
the old fashioned way.

Surge is usually due to a slow / lazy sensor- this will only be apprent at
light to medium throttle when the ecu is running in closed loop. What
happens is the mixture tends to swing too lean and you loose power (but you
wont notice this cos you are applying more throttle than you would do if it
were working fine) then when the sensor reacts and the ecu applies more fuel
you get more power which you notice as a surge.

I am surprised that your not getting any long term fuel trim out of
tolerance error codes though- its possible that the sensor isnt quite bad
enough to cause this tho.

Tim..

 

You're kidding, right? Most "repair specialists" have become nothing more
than parts changers and probably have a hard time spelling multimeter much
less know how to use it.....

Somewhat my thinking also. Maybe somebody at Volvo still has the capability
of doing the process of elimination without doing an engine rebuild??

Thanks for the suggestion, will pass it on.

Jim