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Engine lacks power - "No Boost" - "No Turbo" - "Can't hear turbo":
Precaution: DO NOT jump to conclusions when attempting to identify the cause of having no power. Don't automatically assume that your turbocharger is broken!
Question: Is the power loss intermittent (OK some of the time, weak at other times) or is it weak all the time? If it is intermittent, see 8.e.1 - Intermittent power loss. If it is weak all the time compared to a similar vehicle which is known to be in a similar state of tune but operating properly, see 8.e.2 - Constant power loss.
e.1 Intermittent power loss - Low engine power under some conditions, but runs well at other times
Note: Getting any codes that may be set your ECU (using VAG-COM) will be a major help in isolating the problem. Codes may be set without necessarily illuminating the MIL ("check engine") light.
- Manifold pressure sensor problems. This only applies to A3 and B4 models (i.e. older models - if you have a New Beetle or a '99.5 or later Golf/Jetta, don't even bother reading this section, you have a completely different setup). There is a black hose which connects at one end to the intake manifold and at the other end to the MAP (manifold air pressure) sensor at the ECU. (The ECU is located underneath a black plastic trim panel that also covers the windshield wiper linkage.) The rubber hardens up and leaks at both end connections, resulting in the ECU not seeing a proper pressure signal and causing "limp mode". Replace the hose with a 5 foot length of 5/64" windshield washer hose (about $4 at an auto parts store). It is not even worth investigating whether the hose is at fault, just replace it.
- MAF (Mass Air Flow) wiring harness problems. Did you change the air filter and forget to plug in the sensor? Some vehicles may have aftermarket modifications which involve the wiring harness leading to the MAF sensor ... are these aftermarket devices operating properly with electrical connections all good? Diagnosis of any problems that may exist with such aftermarket modifications is beyond the scope of this document and troubleshooting may be best performed by removing the device in question from the system.
- MAF (Mass Air Flow) electrical plug problems. If your vehicle has a Bosch MAF (see below) there is a technical service bulletin for replacement of earlier-style wiring connectors with a new design having larger electrical contacts.
- MAF (Mass Air Flow) sensor problems. The MAF sensor is located immediately adjacent to the air filter housing. Question: Look at the nameplate on the sensor. Is your MAF sensor manufactured by Pierburg (all A3's and B4's, some European A4's, i.e. all earlier models) or Bosch (most A4's i.e. all later models)? The Pierburg MAF is extremely reliable and is unlikely to be the source of the problem. The Bosch MAF prior to model year 2002 has a poor reliability history. Many owners have had to replace this sensor multiple times (and this is regardless of the type of air filter used). Refer to section 7.l of this document.
- Turbo control system not operating properly. Clogged, leaking, disconnected, or improperly connected hoses that are involved with controlling the turbo boost pressure will create havoc. Check condition and routing, and replace if necessary.
- Turbo VNT mechanism sticking. This only applies to vehicles with a VNT-15 turbocharger ... most A4-chassis models including all A4-chassis models sold in North America, and all 110hp models (A3 or A4 chassis) sold elsewhere. (DON'T READ THIS if your car has a GT15 or K03 turbocharger because they operate in a COMPLETELY different manner.) Locate the diaphragm housing which operates the VNT mechanism (has a single hose going to it, extreme rear of engine compartment, buried down near the bottom right rear of the engine, hose connection faces STRAIGHT DOWN). Locate (by feel with a finger) the linkage rod which points straight up out the center of that diaphragm housing. While feeling this rod, have someone start the engine, and note whether the linkage rod moves - it should. Upon stopping the engine, the linkage rod should move back after a few seconds. If the linkage rod does not operate as described, get a vacuum tester (any auto parts store) and apply vacuum to the VNT diaphragm to see if you can get it to move. If it's seized up, there's your problem. NOTE: To prevent this from happening, DON'T BABY THE VEHICLE when you are driving it, and consider recalibrating the EGR system to reduce the amount of soot build-up in the exhaust.
- Turbo wastegate mechanism sticking. This only applies for those with a GT15 or K03 turbo. If you have a later model, you have a VNT mechanism rather than a wastegate, so see above. The wastegate opens under pressure rather than vacuum. Using a pressure gauge which reads to 30 psi, verify that when you floor it at 2500 rpm, the turbo boost pressure rises to a peak and then drops to about 0.8 - 0.9 bar (12 - 14 psi). Sometimes the wastegate diaphragm gets clogged up with oil from the crankcase ventilation system, and some owners have had success by replacing the red and blue hoses with new clean hoses and cleaning gunk out of the diaphragm housing as best as possible. You're on your own for doing this procedure. To prevent it from ever happening, arrange for the crankcase fumes to not get into the engine air intake ...
- Turbo boost control solenoid valve problems - this is also known as the N75 valve. If you have VAG-COM, and a trouble code of "intake manifold pressure control" is being set, and the problem is NOT a sticky VNT mechanism (see above), the N75 valve may be sticking, clogged with debris, or faulty. It can be removed from the vehicle and the paths through the valve checked by blowing through the various connections with the valve first de-energized, and then energized with 12 volts. Alternatively, obtain a vacuum gauge and "T" it into the hose that goes from the N75 valve to the VNT vacuum diaphragm, and confirm that the vacuum varies under different load conditions while driving. If found to be faulty, some have had success by blowing solvent through the valve to remove any deposits, but replacement with a new one may be the best option.
- Fuel cut-off valve O-ring unseated - especially if the idle speed is intermittently higher than normal. With the engine cover removed, the fuel cut-off valve is located on top of the injection pump just above where the four steel lines go into the end, and has a single wire going to it. Remove this valve (disconnect the wire first!) and make sure the black O-ring is all the way against the body of the valve, then re-assemble.
- Vehicles which have modified engine control systems, especially if a chip and a tuning-box are used together, may experience a phenomenon which has been called "warp field collapse": at full load and generally higher engine speeds, the engine will abruptly go into a reduced-power mode. Investigation of trouble codes with a VAG-COM will generally find a code set which is related to the quantity adjuster upper limit. The problem is that too much fuel is being requested! The solution is to back off the requested amount of fuel, generally through de-tuning the tuning box which hopefully has some manual adjustments that can be made.
e.2 Constant power loss - Vehicle is always sluggish compared to another similar vehicle in a similar state of tune
- If power loss happens below operating temperature and it's OK warmed up, this behavior is normal to some extent.
- If the power loss is accompanied by an excessive amount of exhaust smoke, check all the pipes involved with the air intake system for leaks! A leak on the high-pressure side of the turbo compressor will cause this problem. On later models, the pipe from the turbo compressor outlet (bottom of turbo) to the intercooler is particularly vulnerable because the clamp is awkward to reach and difficult to install properly, so it's prone to blowing the pipe off the turbo. You'll have to remove some lower engine covers to see this pipe properly.
- Dragging brakes, underinflated tires, excessive weight carried in vehicle, slipping (worn-out) clutch, transmission problems which are beyond the scope of this document, etc.
- Incorrect injection timing. See inspection and repair procedure at section 7.k.
- MAF sensor or wiring problems. See procedures described under section 8.e.1.
- Intake manifold clogged. See repair procedure at section 7.g, and see section 7.h for recalibration procedure to prevent this from ever happening.
- Air intake clogged. Inspect air filter and airbox intake screen as described in section 7.c of this document.
- Air entering fuel system. Check the clear plastic lines for air bubbles, and see if the bubbles move when you crank the engine. If air bubbles are found, check all fuel hose connections and ensure that the white plastic "T" that fits into the top of the fuel filter is properly seated with the O-rings securely in place. Refer to section 7.b.
- Intercooler blocked externally. Inspect intercooler for external blockage by leaves or other debris - visible by looking at the intercooler, under the bumper on the left side (A3 cars) / right side (A4 cars), and clean as necessary.
- Intercooler clogged internally. Follow the intercooler cleaning procedure in section 7.f of this document.
- Fuel filter clogged. Replace with a new one per section 7.b of this document. If desired, inspect the old one by cutting it open. If failure was premature, find cause of debris entering fuel system. Your VW has a plastic fuel tank, the debris cannot be from corrosion of your car's fuel tank.
- Poor quality fuel. Fill up at a different station next time.
- Fuel cut-off valve O-ring trouble. See repair procedure described under section 8.e.1.
- Accelerator pedal position sensor malfunction. Check for fault codes with VAG-COM.
Tema: a6 (c4) 2.5tdi problemos su trauka (Skaityta 4746 kartus)
2011 Rugpjūčio 30, 23:30:32 