What really does cause induction contamination? - TAT - The ...

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Murphy’s Law by Nick Murphy This is a story of a late model Nissan Maxima V6 that had a fellow technician a bit perplexed. The technician had been told that the car had not started after being switched off the night before. One would first assume that everything mechanically had to be OK, if it was switched off after driving well. The vehicle had to be towed to a TaT workshop for diagnosis. Was the information received correct? The info could be second-hand and could lead a technician down the wrong path. Our advice is to listen and then ask basic questions. In this case, did the car start and run OK the last time it was driven? Did the car not start after it was switched off? Did it have enough fuel and was the driver using the regular key? The answers – the car started and ran normally until this fault and there was no second key. A simple deduction could be that the car wouldn’t have a mechanical fault if it ran normally right up to switch off. Sometimes drivers might not know if their vehicles were not running properly so information like ‘it was running fine yesterday’ may not be accurate. The scan tool showed code P0340, indicating that one of the cam shaft sensors had a fault and there was no other indication of anything that might stop the car from starting. It was at this point more questions had to be asked of the original repairer, such as, had anyone previously checked codes or disconnected anything prior to us receiving the vehicle. Yes, they said, the front and rear cam sensors had been unplugged to do some tests and there were no codes prior to that. So the basics, like fuel, injector trigger, spark and compression were checked. The rear spark plugs are very hard to get to on a V6 Maxima so only the front three cylinders were tested for compression and all came back with good results. There was fuel pressure and one lot of injector pulse only for every cylinder when first cranked over. This occurred every time. There was no spark or coil trigger at any of the coil-on-plugs, yet no crank or cam positioning sensor codes were recorded. At this point a piece of notepad paper was spotted on the passenger’s side floor. It was a road service note on which was scribbled (P0011) and (P0021). Back to the original repair for more grilling. It turned out that the road service was called to the car before it was towed to the first repairer. They had used their scan tool, extracted the codes and cleared them hoping the vehicle would start, then left the note with the two numbers, but kept the owner in the dark. A very crooked diagnostic path It was at this point the technicians started looking at the problem from scratch rather than relying on previous information or expecting that others had properly checked the basics. The job was to diagnose the problem, give an accurate report and get the vehicle running if possible. The coolant system level and the engine oil were checked. The oil was down about 1.5 litres. The importance of the level of oil in this specific engine and its predisposition to not run if the oil was low was known to the technicians on the job. The correct type and quantity of oil was added, but still no go. The blue sig is crank, red is good cam sig and green is faulty cam sig Not wishing to guess a solution right then, the next step was to go for the serious stuff. The code logged was related to cam phasing issues so why not start there. Scan tool live data showed an irregularity in the cam phase percentages. The oscilloscope showed the cam and crank signal patterns were spot on with good voltage levels and the signal was pulled to ground. So what was wrong with this car? One tip when testing components is to increase the time base on the oscilloscope. It’s like looking through a bigger window, and the view is more extensive. Looking at the crank and both cam signals at the same time, the problems became more evident. The rear bank camshaft was not in line. Variable cam shaft timing can be a bit tricky. There is a lot that can go wrong and it’s not unusual for the mechanism to seize or lock up. Poor oil or lack of oil changes are killers in this area. In this case, the rear camshaft timing was misaligned by more than 45 per cent of its basic idle speed or crank position. The back cam sprocket, which is a two-piece sprocket, had slipped, so the alignment of the three sensors, crank and two cams was incorrect. We believe this was because the lack of oil to the top of the motor caused the rear camshaft to start to grab or seize causing the two-piece sprocket to slip, similar to some harmonic balancers. Crank and cam misalignment can be the cause of a number of trouble codes in some vehicles. The ECU is programmed to pick up a signal and work out if it’s within specs and react accordingly. If a camshaft is out of alignment, some makes of ECUs won’t have a code criterion for it, so it may not log a code for the crank or cam sensor. The German makes are generally pretty accurate when it comes to identifying cam misalignment. You may see common code explanations such as ‘no correlation between crank and cam, crank and cam shaft out of time, cam shaft out of specification or cam shaft not returning to TDC’. Common faults with misalignment are sometimes created by an incorrectly fitted timing belt or variable camshaft mechanism sticking. The quickest way to determine if there is a fault is by looking at the data on your scan tool. Some manufacturers have a lot of data involving the cam timing, such as actual timing compared to desired timing. Looking at data can tell you within seconds what the valve timing is doing. At idle, the cam shaft will not have moved much. If, for example, the data is showing 15 degrees of timing at idle, that would have to be enough to show there is a problem. BMW now have a variable cam lift, where the rocker shaft is moved by a geared motor to change the angle of the rocker. Valve timing and cam lift is going to be a very big thing in the modern vehicle as we try to achieve low fuel consumption and high output. In the wash-up, the problem this vehicle suffered, as with many others, was the lack of proper maintenance. Its oil level was very low, its service history very hazy. The inevitable occurred. In retrospect, it all made sense why one injector pulse was present and there was no spark per cylinder. It was the powertrain control module protecting the engine by shutting it down. Cam layout on rear bank Another gut feel the technicians had was that an unusual noise was noticed from the starter motor while cranking, which turned out to be caused by no compression on the back cylinders. Going back to the basics and scoping the voltage on cranking would probably have identified no or low compression on the back bank and nailed the diagnosis a bit earlier. Many TaT subscribers are reporting that poor maintenance is coming back to bite many clients with later model vehicles. The problem is that motorists are treating them the same way as their previous vehicles which were a lot more forgiving about spaced out services. Once again, client education would seem to be more necessary than ever. Happy diagnoses Nick Murphy The Automotive Technician 18
Mitsubishi rolls out a plug-in SUV Two Mitsubishi cars made their debut at the 42nd Tokyo Motor Show in December 2011 – the Mirage and the Concept PX-MiEV II with its unique plug-in hybrid drivetrain. Also on show was their MINICAB-MiEV light commercial electric vehicle due to be released in the Japanese market during December 2011, and the i-MiEV newgeneration electric vehicle which is currently on sale in Australia. The Concept PX-MiEV II is Mitsubishi Motors’ idea for a mid-size plug-in hybrid with long cruising range. The plug-in hybrid system fuses electric vehicle technology with a small conventional engine, delivering more than 60 kilometres per litre, far ahead of a conventional engine-driven car, with the bonus of high environmental performance. It will cruise on a par with conventional engine-driven vehicles for more than 800 kilometres. High capacity batteries will allow the vehicle to cover more than 50 kilometres in all-electric mode alone, allowing it to be driven solely as an electric vehicle for most the system will start the engine automatically as a generator, and the engine can also be used to help drive the wheels. With the push of a button, the driver can select battery-drive mode for a quiet, emissions-free journey and at the same time switch to battery charge mode while on the move, controlling use of battery power and using the engine as a generator to charge the batteries. A socket on the vehicle allows the electricity stored in the drive batteries to be used to power electric appliances. The Concept PX-MiEV II drivetrain uses a twin-motor four-wheel-drive system mated to Mitsubishi’s Super-All Wheel Control traction control system. In addition to superior handling, the MiEV II provides 100 percent instant off-the-line torque inherent to electric motors, giving it acceleration comparable to that of a 3-litre V6 engine. The Mirage is a five-seater compact, with high fuel efficiency and low emissions. It claims 30 kilometres per litre thanks to weight reduction, aerodynamic body and other efficiencies. everyday AD_AUS_NOV11_TAT_HP:AD_AUS_JUN11_BURSON_HP situations. Depending on power Thailand 17/11/2011 will see the 16:37 Mirage Page first, early 1 in consumption and remaining battery charge 2012. Technical data Timing belts chains & gears Service indicator reset procedures Key programming Manufacturers’ service schedules Service illustrations Repair times Wheel alignment Tyre sizes and pressures Known fixes and bulletins EMS component testing EMS pin data EMS troubleshooter Airbags ABS Air conditioning Electrical component locations Wiring diagrams (for EMS ,ABS, AC & Body) Fascia warning lamp identification Guided diagnostics Tyre pressure monitoring systems Guided diagnostics Electric parking brake Diagnostic trouble codes Battery disconnection & reconnection procedures Clutch replacement instructions (online only) Diagnostic and technical phone support Monthly technical bulletins 4 updates per year (Online) Monthly payments 1300 764 432 www.autodata.com.au AD_AUS_NOV11_TAT_HP The Automotive Technician 19
Page 1 and 2: February 2012 Issue 25 www.tat.net.
Page 3 and 4: You are no doubt familiar with the
Page 5 and 6: educing the compression or the temp
Page 7 and 8: I still believe if a fuel is poor q
Page 9 and 10: Regular a/c service saves plenty Ve
Page 11 and 12: Good vibrations for accessory unit
Page 13 and 14: Please contact your local Castrol A
Page 15 and 16: with Jeff Smit Multisystem Ignition
Page 17: ‘s a fact problem solving AUDA401
Page 21 and 22: Jason Smith Don’t ignore the hidd
Page 23 and 24: YOU SAID IT! Oil and water just don
Page 25 and 26: 4. The sensor is a pressure transdu
Page 27 and 28: No Future? Or Bright Future? Are yo
Page 29 and 30: TECDOC keeps track of spare parts N
Page 31 and 32: ULTRASCAN P1 Built-in CAN Bus Syste

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