’86 Camaro stalls; Does CR-V need valve re-timing?

WHEELS

Q: I have a 1986 Camaro, 2.8litre, that has never been winter driven. When the motor is running at normal hot temperature, the idle will begin to drop while stopped at lights to the point where it will stall. I have had all the plugs, wires and other tune-up stuff done but it hasn’t helped. I was wondering if it might be gummed up fuel injectors from lack of driving. I hope you can help. Thanks.

- Rick A: Idle speed on gasoline fuelinjected engines is regulated by varying the amount of air allowed into the engine cylinders. There are various ways of doing this including BMW’s method of varying valve lift, but the most common method and the one used on your Camaro is with the use of an idle air control motor.

The idle air control motor is a small device that lets air into the intake manifold through a bypass passage around the throttle plates. With the throttle plates closed, the computer varies the position of the idle air control motor so the engine will idle at the desired speed programmed into the engine computer.

In newer vehicles, the computer has the ability to ‘adapt’ idle speed variations and can compensate for faults by changing the position of the idle speed control motor, but in your Camaro, the idle speed motor position is a preset position programmed into the engine computer.

If there are factors that change the amount of air entering in other areas of the engine intake, the idle speed motor will not adapt and only move to pre-programmed positions.

You need to check for either air restrictions into the air intake or vacuum leaks into the intake manifold. The first thing to check is for gum deposits around the throttle plates. If varnish or gum is in the housing, it can be cleaned with a throttle body cleaning chemical and wiped with a cloth.

The throttle plate stop screw should not be adjusted, as this is preset at the factory. If someone has moved it, it could be the cause of the stalling.

It is possible to reset the idle stop screw position on your vehicle by blocking off the air passage to the idle speed control motor and then adjusting the idle speed with the stop screw to about 600 rpm with a warm engine.

Before adjusting the idle stop screw, check carefully for vacuum leaks on any hoses or around gaskets. A vacuum leak will increase idle speed normally, but the computer compensates by closing the idle speed control motor. If the vacuum leak is small, it can cause stalling, especially on deceleration.

Q: On a recent trip to my garage for minor work on my 2007 Honda CRV LX, I was told my next visit could cost me several dollars for valve re-timing. They stated my model has no automatic valve timing and several similar vehicles (2005 to 2008 year) have had to have engine replacement due to cams misfiring and damaging engine walls. I’d appreciate your comments.

- Russ A: Your Honda CR-V has a 2.4litre engine with i-VTEC, which stands for intelligent variable valve timing and lift electronic control.

The system uses computercontrolled electric solenoids to change valve lift and duration of the intake valves and also vary the intake camshaft timing in relation to the exhaust camshaft.

These are two separate systems with combined operation to maximize performance and fuel economy while minimizing exhaust emissions. If there is an electrical problem with the system, the engine computer will set a code and turn on the check engine light, but a hydraulic problem may not cause a code to set and yet still prevent the system from working as it should.

From your description, it would appear that the repair shop has determined that the variable valve timing is not working properly. This is often caused by some sludge or deposits blocking a fine filter in the oil passage of the electric control solenoid.

This could cause engine damage is you continue to drive over extended periods due to inaccurate valve timing, but would only cause a performance and fuel economy decrease in the short term.

While it is possible to clean the filter screens in the solenoids, normally the solenoids are replaced with new ones.

The solenoids are relatively inexpensive so this is typically the best way to go.

Justin Pritchard is an automotive consultant and a member of the Automobile Journalists Association of Canada (AJAC). http://justinpritchard.ca/