Hello all,

I'm the proud new owner of a 1996 850 turbo, hehe. I recently added a "boost control valve" on the wastegate vaccum hose to increase the boost just a tad. Everything was going well untill yesterday; the "check engine" light came on. The car still drives, turbo produces boost, but it is as if the boost is not reaching the engine! I do not have an OBDII diagnostic tool handy. Does anyone have the slightest idea on what could've happened? Could the wastegate have stayed stuck in the open position? If so, would the boost guage still read boost?

Any type of help is greatly appreciated,

Nik

 

Check all the turbo and vac lines, maybe you blew something.
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+1

 

I wish someone would tell me how the wastegate is controlled on our Volvo 850(s).

From my very limited understanding,

Unlike most other makes of cars, our wastegate is controlled electronically by the ECU -- not mechanically via boost/vacuum hose on cold-side intercooler pipe.

Therefore, if you install a traditionally boost controller to bleed off excess air pressure from the wastegate, the ECU will compensate and ask the wastegate to bleed off even more air.

Besides, isn't there a procedure to calibrate the wastegate arm -- such that the wastegate opens precisely when the ECU asks it to?

 

It is all controlled electronically and under vaccum(actually pressure) from the boost control valve. The Ecu tells the valve how much to open the waste gate.

 

Well, why after installing this mechanical device was I able to attain a lot more pressure from the turbo? And by more, I mean a lot more; my turbo guage read to maybe a 1/4 into the white part before, and now it just bottoms it.

For my check engine issue, I finnally found someone with an OBDII wire and a laptop w/ autotap. My O2 sensors were at fault... We did a reset on the check engine and now everything is back to normal... for some reason. I still need to replace those sensors.

 

Hello Nik,

If your state/country does not require emissions test, I wouldn't worry too much about the O2 sensors. They are $$$,and turbo models have 2 of them. One is about $170, the other is about $200 and the end result seems negligible. But if the CEL appears frequently, then it might pay off to change them. Are both sensors bad, or is it just one?

Good luck,


JPN

 

You can get Bosch universals to work, you just need to splice them in and use solder, not clip connectors. I know a lot of people believe you must go OEM with these, but I put two new universals in for under $50 total.

O2 Sensors do have a pretty large affect on mileage, so they can save you $$. The problem is, even if you buy them FCP Groton, it'll take a long time to save $250 in gas - AB

 

Did you install a manual valve or electronic valve?

 

It's like an ajustable mechanical check valve: Open under pressure, closes with vacc.

 

That sometimes will bypass the electrical part making the car act funny.

I have seen some people hook one up and not have problems and others have a ton of problems.

 

I'm pretty sure Bosch is the OEM supplier of the factory O2s

 

I'm pretty sure B1mmer does not frequent these forums. l0ol