Sluggish 1994 855T Turbo

[rsmigel]

Wife's car just threw a "check engine" light on the highway and read as a P0171. No other codes stored and this the is first CEL I've seen on this car in years.

I drove the car and noticed very low turbo boost... only 1/4 of the way in the white scale (I've got another boost gage coming and will report back with a more accurate reading) Performance matches the gage: sluggish with little torque. Gage on vacuum side looks good, 3/4 to the far left on deceleration and 1/2 on idle.

EGR system was replaced 25K miles ago. All vacuum hoses were replaced with blue silicone lines at the same time. Mileage is currently 181K.

I popped the hood and checked the big turbo hoses and every vacuum hose I could trace without dis-assembly. Everything looked fine.

Drove car another 100 miles w/o CEL light coming on. Added a can of octane booster and saw no performance improvement.

The car burns no oil. I checked the action of the "Turbo Boost Pressure Valve" and it appears to be working properly with a 12V signal.

I have an ACTRON CP9575 ( https://actron.com/sites/default/files/ ... nglish.pdf ) to use for further study if it will be of any help.

Suggestions???

[theWIFES_S70]

Have you read through all of this: https://www.matthewsvolvosite.com/forums ... =1&t=21109

[scot850]

Try pulling a vacuum on the CBV (compressor bypass valve). They have a diaphragm that splits with age preventing boost. On you car it should be possible to fit a new diaphragm without removing the turbo. Also the TCV is also a good culprit, especially if the original. It may be getting 12V but they start to stick with age and again prevent boosting.

The linked article is excellent for other areas to check. Turbo pipework and intercooler are other places to carefully check.

Neil

[Ozark Lee]

^^ This.

The intercooler lines can also develop leaks that are tough to see without actually removing the hoses.

...Lee