Clutch slipping in reverse a tricky one

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This article was published 12/05/2017 (3380 days ago), so information in it may no longer be current.

Question: I have a 2001 Toyota Echo with a 1.5-litre engine. It appears my car has a slipping problem when it’s in reverse. The car drives just fine when going forward. However, to reverse the car, you first have to generate momentum — regardless if it is forward or reverse momentum. If you put the car in reverse and it is standing still, the car will not go anywhere when you release the clutch. What do you think the cause of this is and is it repairable or is the transmission and/or clutch shot?

— Gabe

Answer: This is a strange symptom. If the clutch slips in reverse gear, it should also be slipping in the forward gears. Since your Echo drives fine in forward directions, the problem is not in the mechanical clutch itself.

If the problem was in the manual transmission, then I would expect you would hear grinding noises or clunks as it slips out of gear, so I don’t think the problem is internal in the transmission.

Instead, the problem is caused by something external and there are only two external connections that affect gear selection: the clutch hydraulic system and the shift linkage.

When pressed, the clutch pedal forces fluid from the clutch master cylinder, through the hydraulic system and into the slave cylinder that is mounted on the transmission.

If the slave cylinder bolts were loose — so that the slave cylinder could move when engine torque is applied in reverse — then it may prevent full engagement of the clutch. This is a long shot, but worth checking.

The other possible problem could be with the shift linkage at the transmission. It may be missing a bushing, worn, or have loose mounting brackets.

It is also possible that an engine mount is broken, allowing the engine to rock in its mounts when you step on the accelerator in reverse gear. This could cause the transmission to slip out of gear so it doesn’t move.

You can have someone watch the engine while you try to drive ahead and back a couple feet. It is normal for the engine to rock a little in its mounts, but there should be no big movements of about 25 millimetres or more.

If it rocks too much, look for broken engine or transmission mounts or missing mount bolts.

Question: I have a 1986 Camaro 2.8-litre that has never been driven in the winter. When the motor is running hot, 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 tuneup stuff done. It hasn’t helped. I’m wondering if it might be gummed up fuel injectors from lack of driving.

I hope you can help.

— Rick

Answer: The computers back in 1986 were very simple compared to today’s and couldn’t adapt to airflow changes quickly like current vehicles do.

Usually stalling is caused by insufficient airflow into the engine at idle.

There is an adjustment screw on the throttle plates, but this is set at the factory and should never be touched.

Instead, airflow may be restricted by varnish or gum deposits built up on the throttle plates and in the throttle housing.

Using a throttle body spray cleaner and soft rag, you can wipe those gummy deposits away.

The idle air control motor on these early fuel-injection systems were also notorious for sticking.

The idle would be too fast so it would command the idle air motor to close and slow the idle.

But a sticking motor would move in jumps instead of smoothly and can cause the vehicle to stall.

Replacing the idle air control motor is the recommended fix, but do not have the ignition on unless the idle air control motor is installed and connected electrically or it will move to the wrong position.

Finally, a dripping or leaking fuel injector can cause the engine to slowly slow down and stall.

You may be able to see fuel dripping from the injectors (instead of a fine spray) when the air cleaner is off and the engine running.

I use a timing light to watch the spray and it makes it much easier to see large droplets.

If there are large droplets, you can try running injector cleaner with the fuel or have them cleaned at a fuel injection shop.

Worst-case scenario is that you will need to replace the injectors and that is relatively simple to do.

james.kerr@sasktel.net