This is an update to my original post titled: 850R with Sporadic Boost Issues.

Since this original post, I have replaced all vacuum hoses from the turbo control valve to the intake, turbo, wastgate, etc. From a drivability standpoint, the car has certainly become more predictable. Before, there were no guarantees as to what would happen when you put your foot in it. Sometimes acceleration was uninspired, other times the thing would take off like a raped ape.

Also, prior to replacing all hoses, the car had begun to throw engine codes (front O2 sense slow response, and non response from the turbo presure control sensor). Replaced the bad hoses, cleared the codes, no new cod3es since. However, I'm kinda back to the original issue, which is that I feel like there should be more power than there is. Any thoughts on the subject are greatly appreciated!

BG
Orlando, FL

BG,
Question? Now that all of the hoses are clean, have you examined the plugs? Are you using gasoline from a reputable station, 92-3 octane? Is the fuel filter fairly new?
If you floor it from a standing stop, do the tires start to slip when you reach 25mph (TRACS turns off then)? If that happens, you got all the boost! :)

When I was in Colorado Springs, it would almost flood out until the rpms hit 2,000 and the boost started. Not enough air!! Hows your air filter?

Klaus

Update: I have cleaned the throttle body which had some gook in it. Also checked the ignition, plugs, plug wires, etc. New air filter. Think I will change out plugs and plug wires just on general principle. Recommendations?

All seems OK. No difference. GLT performance, or at least until this morning. Was accelerating from a light this morning and the turbo woke up and threw me back in the seat.

One thing that hit me over the weekend... I had my ABS unit rebuilt a while back. The whole trouble with turbo response began right around that time. Bizarre coincidence or is there something to that?

BG

Update: I have cleaned the throttle body which had some gook in it. Also checked the ignition, plugs, plug wires, etc. All seem OK. No difference. Car runs fine, but I continue to be unimpressed...

One thing that hit me over the weekend... I had my ABS unit rebuilt a while back. The whole trouble with turbo response began right around that time. Bizarre coincidence or is there something to that?

BG

Now that we have email again, I found your post.
Check around the ABS module for ANY loose vacuum lines. There is a lot of junk around there which could get pinched.

Klaus
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Please answer your responses. We need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

Yep...

Checked all that and replaced many suspect hoses in that general area. Here's another interesting tidbit: Most of the driving I do is stop and go traffic, however this past weekend I had it out on the highway for 20-30 miles. Boost performance was basically the same EXCEPT if I coast for 5 seconds and then accelerate again.... WOW! Power and boost to burn! Speaks to vacuum and manifold presure perhaps? Any ideas?

There's a solution here somewhere. Once in a while, I get glimpses of how this car should be running. I'm going to keep digging until I find the answer....

BG

Hmmm. You are running too rich and your plugs got fouled. When you coasted, the plugs cleaned off and then you get to have fun!!!
So why is it running too rich? All new vacuum lines should have made for an air tight system. Perhaps your car just needed a good "tune up" at higher rpms?

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

Update: Switch the brand of gas I use. Marginal improvement. Could fuel pump pressure be causing this? Or perhaps cooling of the charge from the intercooler? After all, this is a black car in FL. Runs better at night when it's cooler outside.

There is a vacuum operated compressor bypass valve on the turbo. (not the waste gate) I was having problems with low boost and found that the diaphragm on this valve was broken and leaking. Perform a vacuum test on this valve. It should hold a vacuum. The vacuum hose to this valve connects to the vacuum tree on the throttle body.
Good luck.........

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Tom 69-1800S, 72-1800ES, 96-850T,2000-S70 GLT-SE

What you say about cooler air is true, but if it ran fast before that should not be an issue. You have a boost gauge, does that get nicely in the white area?
I wouldn't suspect fuel pump or delivery. If your gas milage is that bad, it could be related to a failing MAF sensor, which can be cleaned. Check the wiring there also.
Get your codes read and see if there are any lurking around. Inspect the plugs for fouling.
As for new plugs, I just get Volvo plugs and Bougicord(sp) wires from FCP. Not cheap, but better than the dealer. Verify the gap before you install the plugs.

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

Have not looked at the plugs. Ignition wires look OK. Will pull a plug and see what they look like. I used to get some tire spin when I first got the car. Not anymore. That's why I think something is not right. Mind you, I don't beat on this car. This has become more of an issue of fuel economy. I have to put my foot much further to get the car to go. It has affected the gas mileage. Used to get 20-21 around town. Now I get 16-17. 93 octane gas every tank full.

You might want to think about cleaning the throttle body, the butterfly could be sticking. They can get gummed up over time and have an impact on combustion air flow.
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Wallie

You might want to think about cleaning the throttle body, the butterfly could be sticking. They can get gummed up over time and have an impact on combustion air flow.
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Wallie

Also check your throttle cable is wound onto the throttle assembly correctly and not too loose, I had similar syptoms to yours, and it turned out to be a duff throttle cable...