QuestionHello, i have an 2002 gti 1.8t, this past weekend i drove about 600 miles to visit my friend, 300 miles each way. i just hit 78k. i was driving to work this morning and when i was picking up some breakfast the MIL illuminated. I work for Toyota, and got the gti 3 months ago, i am not familiar with them. the freeze frame said too lean and it threw the MIL at idle. I cannot find a vacuum lea, but it seems as though i can hear one from underneath and from up top. in second gear @ 3k rpm im at full boost and then on my boost gauge it drops down to half boost and then will kick back in at full boost about 400rpm later. not too sure if its the MAF meter or not.
AnswerHey Derek; It's probably not the MAF. There are 2 devices on top that could cause a vacuum leak sound if they are either not hooked up, or if they are broken. One of them is the turbo recirculation valve, right next to the bulkhead about 1/3 of the way over from the left to the right...driver's side toward the passenger side. The second one is the "Combi-valve," black plastic, and at or near the air inlet tube from the air box to the MAF.
My guess however, is perhaps, neither of them. Look for a split vacuum hose that goes to the "suction jet pump." Good luck finding this device without a guide dog. The "suction jet pump" is under the lower plastic cover with 2 DZUZ fasteners in it. It's the narrow one that goes around the intake plenum. Under it you will find a black sheet metal holder bracket that has 2; 5, or 6 mm hex drive bolts...I think they are 5's. There are several solenoids attached to the bracket too, and the electrical connectors need to be removed to get any play in the bracket, so you can get to the "suction jet pump." My advice right here and now...replace the "suction jet pump," replace the "3 way crank case breather hose," flush the crankcase, and oiling system, and start using nothing but synthetic oil, and start replacing your oil filter, and oil at 2500 mile intervals...at the longest. That little turbo engine make big power, and torque for less than 120 cubic inches, but it does so by making HUGE quantities of HEAT. The oil breaks down, the carbon deposits form, and they clog that little orafice in the suction jet pump, which in turn builds crankcase pressure, and splits the hoses, and vacuum lines that are associated. At 78,000 miles I am willing to guarantee trhis is the problem you are facing. Have lots of gloves to protect your hands, and bring your patience, because they used those little crimp on clamps everywhere. Side cutters, and end cutters are a must. Good luck, Derek. It will take the better part of a day to get this stuff changed out, and when you do get the suction jet pump out cut it in half lengthwise, and just look at all the crud in there.
