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This sounds like over boost fuel cuts.
If the PBV is leaking you get a boost and do not get decent pressues at all so this cannot be the source of the over pressure.
If the BPV will not open or there is a fault in its VAC line, then there will be a pressure spike in the turbo piping only when the throttle is closed during a run with boost. But even if this does happen, then the MAP sensor down stream of the throttle will see manifold vacuum, not boost. So again the BPV cannot be resposible for a oper boost fuel cut.
If you had a 2000+ T7 ECU then a boost leak via the BPV could create a mixture problem because of the interaction with the air mass meter on these models. But that is not what you have on your 99SET.
So not the BPV... which some love to call a hooter valve.
So what is the problem? I think that by your description that you have an uncontrolled boost situation. Lots of power coming on when this happens? If so, there could be a leak or split end on the MAP sensor VAC line, or a problem with the BPC valve. Check the VAC lines to and fro the BPC valve for good measure. Also when cold, grab the wastegate actuator arm and move it by hand, looking for some binding or other problem. It takes a surprising amount of force to move it.
Has any one tightened down the wastegate actuator to increase the boost?
Does the engine ignition ever miss. It is possible to have a non ignitied fuel charge ignite in the hot exhaust manifold and that could give the turbo's turbine a good boot in the pants which would create an increase in boost pressure. Any difficulty starting? That would indicate dirty injectors which could contribute to such problems.
You can confirm that the BPV is working very easily. If should be open when the engine is idling. Remove the 25mm return hose and you can feel if the valve is open with your finger. Remove its VAC line and the valve will close. Don't get your finger tip pinched!
posted by 209.172.2...
, Sat, 12 Jan 2002 12:59:04
, Sat, 12 Jan 2002 00:01:02
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