Diagnostic Solutions: Diagnosing Misfires
Although diagnosing misfires can be a tough assignment for any driveability technician, the diagnosis can be made much simpler if he understands the basics of misfire diagnosis. For example, when the first OBD II misfire monitor was first introduced in 1996, technicians were puzzled by problems with false misfire diagnostic trouble codes (DTCs). Case in point, vehicles being driven on washboard dirt roads began recording false misfires.
Tech Tip: VW’s MIL is On, with DTCs P0087/P1093 or P2293
This condition could be caused by excessive wear of the intake camshaft lobe that drives the high pressure fuel pump. The wear limits maximum pump piston lift, causing fuel rail pressure fluctuations. The wear on the camshaft lobe can also lead to wear on the base of the high pressure fuel pump cam follower.
Solving Common Honda Driveability Problems
One of the common check engine light problems you’ll encounter on Hondas is a misfire code with no apparent misfire. Many times, this problem will be traced back to tight valve lash. Obviously, a tight valve will pass the audible test every time. But, it’s the tight valves that will set the check engine light in the best case, and if it’s ignored long enough you’ll be looking at a low-compression situation caused by a burnt valve.
Diagostic Dilemmas: Lost in ‘The Diagnostic Woods’
This real-world case study of a 2002 Chevy S-10 pickup, a 1995 Buick and a 1995 Lincoln Town Car illustrates why “chasing” trouble codes can get you lost in the Diagnostic Woods.
Tech Feature: Courage Under Misfire
Generally, when a customer brings a vehicle into a shop that has a misfire concern, they will describe it as bucking, jerking or loss of power. They also may describe it, depending on the cause, as a jerking when they take off from a start, but smoothes out once the vehicle gets moving. They may tell you the check engine light has been flashing.
Tech Tip: Nissan Engine Will Not Crank with Outside Temperature Below 10
A no crank condition may call for replacement of the Intelligent Power Distribution Module-IPDM.
Tech Feature: Brake Job on Ford CVPI
The Ford Crown Vic Police Interceptor, or CVPI, has been around since 1992. The current crop of CVPIs do not differ much mechanically from their predecessors, but on the undercar electronics, the vehicle has advanced dramatically in the past 10 years.
Tech Feature: Mazda6 and Mazda3 Driveability Diagnostics and Electronic Throttle Control
Drive-by-wire throttle control systems are pretty much trouble-free but have to be taken into consideration as you perform routine service and diagnose problems, and it changes the way you service these cars when it comes to cleaning the throttle plates, advises Bob Dowie, import specialist contributor, who also covers electronic throttle control’s tie in with ABS and VSC systems.
Tech Tip: VW/Audi Throttle Body Alignment
Have you had a customer pull into the shop with a Volkswagen or Audi that just will not idle correctly? One of the possible causes is that the throttle position is not known. The ECU must know the full range of motion of the throttle in order for it to properly control the engine.
Ford Tech Tip: Can’t Escape Intermittent No Crank with MIL On
Some 2001-’04 Ford Escape vehicles may exhibit a powertrain control module (PCM) concern that results in no crank, no start or malfunction indicator lamp (MIL) with one or more diagnostic trouble codes (DTCs) present.
Tech Feature: The Changing Face of Automatic Transmissions
Today’s computer systems have completely redefined automotive operation, particularly when it comes to transmission control.
Tech Tip: Saturn Crankshaft Position Relearn/Adaptives Reset Procedure
You may see a tell-tale service light flashes after replacement of the ECC on 1996 and newer Saturn vehicles. When this occurs, a Crankshaft Adaptives Reset Procedure and Crankshaft Position Relearn Procedure (Flash) must be performed.