QuestionQUESTION: I ran a scan tool on my 2005 Volvo S40 AWD. The car goes in to limp mode if I apply too much load. The car has no power and very slow acceleration I need to turn the ignition on and off to get it to clear. I purchased pro scan software and observed a 2 psi dip in fuel pressure right before the problem occurs. Is a 2 PSI drop normal?
ANSWER: Raymond, hmmmm, tell me what scan tool can measure "a 2 psi dip in fuel pressure"? It must be very magical.
Seriously, a 2psi drop is normal and you could see it on a properly attached mechanical fuel pressure guage. NOT on a scan tool. Does your scan tool show any codes??? How do you know it's in limp mode?
Mark
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QUESTION: Thanks for the info Mark. The car does not show any codes including temporary. I believe the car is in limp mode because it does not accelerate at all. The turbo will not build boost, its as if there is no turbo. Once the ingnition is turned off, the power returns until I hit the magic trip point with too much acceleration/load.
ANSWER: Raymond, I would check the charge pressure regulator/wastegate settings. It may be overboosting throwing it into limp mode? The ECU does monitor charge pressure=turbo boost, and if it goes past the predetermined (pop off) setting it will shut her down. That should set a code though. Does your scanner read Volvo codes or only generic OBD II ? Overboosting is not a mandatory OBDII parameter to be monitored. It may only be in the Volvo codes. Test the boost sensor also. HTH
Mark
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QUESTION: Pro Scan appears to only measure generic codes. Have you seen boost levels increase as the vehicle gets older? I was worried that the manifold pressure sensor may have aged and senses boost levels higher than actual. I guess my next step is to get a boost gage. What boost levels should I expect in 1st and 2nd gear (2005 volvo S40 AWD)? Really appreciate your advice.
Answer Raymond, "I was worried that the manifold pressure sensor may have aged and senses boost levels higher than actual." This is my suspicion also. Unless someone has tinkered with the wastegate or the computer prom., these things do not typically change over time except to lower the pressure with wear. I'm afraid some "gearhead" previous owner may have cranked it up on you????
Mark
