Autocare 21 February 10

Rough idling (lead)

I HAVE a 1997 Camry SXV10.

Recently, I noticed that when it was idling, the engine was running rough, sort of like misfiring (the engine would intermittently shake a bit).

I tried to check for the DTC but did not find any fault code.

When I disconnected the oxygen sensor signal to the ECU near the exhaust manifold, the rough idle appeared to get a lot better.

I have done the following checks:

1. Vacumm leak for PCV, EGR, master brake pump and check for any hose leak.

2. Tested the oxygen sensor feedback voltage Vf1 to E1.

3. Swapped the distributor, igniter, spark plug and cable with a re-cond unit but there was no improvement.

There is no problem in starting the engine and it is running perfectly, idling normally at 800 rpm. The only problem is rough idling.

I am not sure whether the engine is running too lean or too rich.

Fuel consumption is slightly higher at 7-8km/litre for town use. It used to be about 8-9km/liltre.

Is there something wrong with the oxygen sensor or other sensors? Or is the ECU faulty?

- Tan

Reply:

Misfires are always very difficult to track down particularly in modern cars with all the electronics.

Since it appears that you have done some basic checks to fault-find and still cannot locate the misfire, I would suggest that you get a Toyota service centre to put it through a full check-out because the fault may be in the harness or one of the other sensors.

Wheel alignment

DURING alignment, normally the balancing and toe are checked and adjusted.

As for camber, most cars are not adjustable but some mechanics will recommend it to be corrected with some nuts or pumping the wheels sideways.

1. Would this damage the wheels or drive system and render the car unsafe?

2. From experience, the camber correction is expensive and will continue to go out of specification.

How will the wear of the tyres be like if they are only balanced and toe adjusted without correcting the camber?

- Wornout

Reply:

I cannot see why the camber of the wheels can go so far out that the chassis needs to be hydraulically moved or special camber bolts put in.

If that were the case for a car that is never abused, there is a serious manufacturing defect as there is insufficient strength in the front end of the car.

Usually, this type of work is done with cars that have had front end accidents or have damaged the suspension or there is a need for negative camber for competition purposes.

If the camber of the wheels is excessive (i.e. way above the factory specs), there is the possibility of severe tyre wear.

So, check out first if your alignment readings are out of spec before doing any additional modifications.

Quieter tyres

I AM the owner of a 2005 1.5 Vios E.

I need advice for new tyres that are quiet, relatively cheap and able to give good mileage.

How much less does the same tyres cost in Port Klang? Where can I get honest brake tests?

- 019-2335233

Reply:

I would suggest that you talk to your tyre shop and see what they recommend.

Generally, tyres with a fine tread pattern tend to be quieter.

I do not know about tyre prices in Port Klang.

If you want a brake test that will give you printed results and accurate repeatability, I think the best people to go to would be Puspakom.

Of course, some franchise holders have brake testers in their service workshops that you could go to, and all assembly plants have brake testers but this equipment is not available to the public at large.

ECU quandary

I BOUGHT a used ECU (engine control unit) from Australia for my 1977 Grand Cherokee.

The problem is every time I start, the engine cuts off and the check engine sign comes on.

I was told that this ECU has an immobiliser but no one knows how to by-pass it.

- KPC

Reply:

Sorry, I have no details of the ECU.

Maybe you should speak to the local franchise holders of the car you are using and see if they can help.

Otherwise, look for anyone who is repairing this model.

Battery upgrade

I HAVE just received my new Alza MPV (multi-purpose vehicle).

I intend to upgrade the in-car entertainment and install additional electronic gadgets.

Can I change the current car battery from NS40 to NS60?

- Stephen Lee.

Reply:

There is no problem with changing your battery to one with a higher capacity provided the compartment can take a larger one.

What you need to remember is that however large the battery capacity, it still needs to be recharged if your current draw is more than the output from the alternator.

In other words, you may find that the battery would run down at night because that is when the draw is the highest and it recharges in the day.

Cylinder head

I REFER to your answer regarding the skimming of a cylinder head.

You stated: "...running hot even if the ignition timing is advanced further...".

This is absolutely wrong. If the compression ratio is increased, the ignition timing should be retarded, since flame propagation is increased.

- Joep

Reply:

You are right! I stand corrected. The reason is that the air-fuel mixture ignites much faster than normal, to the extent of detonating.

Having said that, in many cases even retarding the ignition timing alone would not help and other measures have to be taken.

Clutch slip

I AM driving a Proton Saga BLM and when I engage the 5th gear, the rpm meter reaches 4 while doing

120km/h.

I can hear the engine sound as though I am ramming the car using the 3rd gear.

Is this normal?

- 016-4458443

Reply:

It seems to be a rather high rpm for an overdrive gear.

Are you sure that the clutch is not slipping?

While driving in this gear, try accelerating hard and note if the rpm goes up not in proportion to speed increase.

If so, there is clutch slip and you need to get it adjusted or replaced.

Tyre rotation

SHOULD tyres of the Nissan Grand Livina 1.8 be rotated at 5,000 or 10,000km interval?

- 012-4941309

Reply:

What does your Owners’ Manual say? Personally, I would rotate at 5,000km because at 10,000km, there would already be quite a lot of wear (of course depending on the car).