Driveability Archives - Page 6 of 13 - UnderhoodService
Tech Tip: DeLorean Fuel Pump Replacement

DeLorean owners and enthusiasts know to be wary, a car left sitting that long and havoc ensues with the sensitive fuel system of a 25-year-old DeLorean. In fact, any car, left sitting for a lengthy period of time will eventually encounter fuel problems. One specific problem to note would be the need for a new fuel pump. Cars left sitting, and even daily drivers, can fall victim to fuel pump failure. Over time, debris and contaminants build up in the fuel tank.

Diagnostic Dilemmas: When Over-Voltages Electrocute PCMs

During the past nine months, I’ve had three instances of powertrain control module (PCM) failures on Jeep Wrangler vehicles that were evidently caused by an over-voltage condition. The first case involved an owner who requested that a local shop replace the fuel pump because his 1998 Wrangler was slow-starting in the morning. The shop found the pump pressure was marginal and replaced the pump. Because the Jeep still had the problem, the owner complained about the fuel pump, first to the shop and then to the local jobber supplying the pump.

Coil on Plug Ignition: The Wired Differences

For late-model vehicles, the norm is one ignition coil per cylinder, commonly known as coil on plug. The task of providing voltage potential to each spark plug is performed so reliably that it’s easy to take for granted. An underhood comparison of a variety of vehicles, however, reveals there are subtle differences among coils. For example, each individual coil may be connected to two, three or four control wires.

Tech Tip: GM Vehicle has DTC P0757 Set, MIL Illuminated and Slipping Transmission

Some customers may comment on any of the following conditions – an illuminated MIL (where DTC P0757 is found as a history code), no third and fourth gear and the the transmission does not shift correctly.

Tech Tip: Kia Optima Won’t Rev, Sets Code P0350

On some Kia Optima vehicles, a P0350 code is set, indicating a faulty ignition coil circuit. At times the engine runs bad and won’t rev up; that is when it sets the code.

Directions: Vehicle Age and Smaller Engines Increase Vehicle Maintenance

While the small increase in 2010 vehicle total mileage would seem to be negative for aftermarket product expansion, the changing driving habits of Americans are causing more vehicle wear per mile driven today than in the past.

Tech Feature: Common Rail Systems May Soon Be Commonplace

Due to the conflict between consumer performance demands and more stringent EPA standards, the use of

Tech Tip: VW’s Check Engine Light is On with Fault Code P0411

When diagnosing various VW and Audi vehicles, the Check Engine Light (MIL) is on and fault code P0411 (16795) is stored in the fault memory.

Wrangling in Jeep Spark Timing Dilemmas

Every once in a while I get a Diagnostic Dilemma that takes me back to the basics of how modern engine management systems work. This month’s happened to be a 1992 Jeep Wrangler equipped with the 4.0L engine and manual transmission. Of course, a vehicle of this vintage and configuration has to be about as basic as modern technology can get, right? Well, there are always exceptions.

Tech Tip: Nissan’s Engine Idle Speed is 25 RPM too High

If you confirm the idle, in Park or Neutral, is more than 25 rpm above specification (with the engine warm), and/or DTC P0507 (ISC System) is stored, this incident may be the result of recent cleaning or replacement of the throttle body. The vehicle “in-use” learned idle may be higher after throttle body deposits are reduced (by cleaning or replacement).

Ford Reflash Tech Tip: PC Settings

So, you’ve just finished up a Ford, and you’re about to try and start it up. However, it needs programmed. You’ve decided to use a J2534 tool, but there are certain things you’ll need to consider before purchasing that subscription at

Service Solutions: Lessons Learned Regarding ‘Old School’ Ignition Diagnosis

Recently, I’ve been confronted with driveability complaints on older vehicles that appear to defy conventional wisdom. Diagnosing such problems usually forces me to re-examine the fundamentals of engine