Archive for July, 2017

The magic computer? We still don’t have one.

Thursday, July 20th, 2017

“Do you have one of those computers that tells you what’s wrong with the car?” This has got to be one of every mechanic’s least favourite questions to get from a customer. As we’ve explained before, while scan tools can provide a starting point for a proper diagnosis, it’s very early in the process that the human brain must take over. As we often tell people, there is a big difference between pulling out a trouble code and actually diagnosing a problem.

Here’s a great example from this week. This little Honda CR-V came to us with a “check engine” light on, and the engine idling rough.

airdrie check engine light

 

We connected a scan tool and retrieved the stored trouble codes from the engine computer, or ECM. As we often see, the stored codes were of no help, as the engine had set misfire codes for all four cylinders. We already knew the engine was misfiring, and the trouble codes don’t tell us why the misfire is happening.

airdrie car scan

 

Even though this vehicle’s rather simplistic engine computer is flagging misfires on all four cylinders, the issue really felt more like a consistent misfire from a single cylinder. Removing and shorting out the spark plugs wires one by one, we determined that the engine was misfiring on cylinder #4.

airdrie spark plugs

 

OK, now what? We’ve got lots of possibilities here: the issue could be a bad spark plug or plug wire; a problem with the distributor (yes, this car still has one); a faulty fuel injector; or about a dozen other things. Removing and inspecting the cylinder #4 spark plug seemed like a good place to start. As it turns out, the spark plug and wire were both in good condition.

airdrie mechanic

 

We noticed, however, that the spark plug was a bit wet with fuel. Having already ensured we had a strong spark supply to the plug from the distributor and coil, this could only mean one thing: The spark plug was firing; the fuel injector was firing; but the combustion event was not taking place inside the cylinder. The next logical step seemed like performing a compression test. We installed our compression tester in the #4 spark plug tube; disabled the ignition system; and cranked the engine over. As it turned out, cylinder #4 was only making about 40PSI of compression! (A good cylinder on this engine measured around 160 PSI.)

airdrie compression test

 
The low compression was definitely the cause of the misfire. Every engine needs at least 100 PSI per cylinder to “get the fire going”, so to speak. Now it was time to determine why cylinder #4 had low compression. Like before, there are lots of possibilities: it could be a burnt/bent valve; worn out piston rings; or a handful of other things. How do we determine where all that lost compression is going? We install a cylinder leakdown tester. Out came the compression tester, and in went this next tool.

airdrie car repair

 

We rotated the engine until cylinder #4 was on its compression stroke, with all the valves closed. Using the leakdown tester, we filled the cylinder with compressed air. As you can see, this cylinder has about 85% leakdown. (20% is the most we’d ever like to see on a good engine.)

We can also use the leakdown tester to determine where the leaking compression is going, by listening for air leakage at different points on the engine. Air coming out of the intake manifold or throttle body indicates a leaking intake valve on this cylinder. Air hissing from the tailpipe indicates a leaking exhaust valve, and air leaking from the oil cap points towards a leak into the crankcase via worn out cylinders and/or piston rings. This vehicle had none of these leaks. The compressed air was actually leaking from the cylinder #3 spark plug hole, indicating there is a blown head gasket or other combustion leak between these two adjacent cylinders.

The next step in diagnosis will be to remove the cylinder head for inspection, and likely replace the leaking head gasket.

 

Almost every warning light diagnosis works this way. The trouble codes (sometimes) provide a starting point, and then there are usually many other tests that must be performed – using even more specialized equipment – to “zero in” on the route cause of the issue. With some issues, there are no codes stored at all, and the technician must let the symptoms and their experience lead them in the right testing direction.

Every good diagnosis goes like the one on our Honda this week: A well-trained technician knows exactly what test to perform next based on the symptoms at hand, and lets the results of that test tell them what test should be performed afterwards. There is no wasted time troubleshooting parts that don’t need to be checked – and more importantly, no money wasted replacing parts that won’t fix the problem.

This is the value of a good diagnosis by a qualified professional, and it’s what we work to bring you every day.

Getting the most out of your air conditioning system

Friday, July 7th, 2017

July has barely begun, but we’ve already been inundated with some very hot weeks in Alberta! Naturally, we’re doing lots of air conditioning repairs these days. But what if your air conditioning system works, but it doesn’t cool as well as you’d like? Here are some tips to maximize its effectiveness.

 

Change your cabin air filter.

Cabin what? We still run into a lot of people who won’t know their car has a cabin air filter! Your cabin air filter is the “furnace filter of your car”, filtering the air travelling through your heater vents. The effect a restricted filter can have on air conditioning cooling is dramatic! A plugged filter not only drastically reduces the force with which the air blows from the vents, but it also reduces cooling. Check out this vent temperature comparison we did on a vehicle with a very dirty cabin air filter:

air conditioning repair

We don’t charge any labour to replace cabin air filters on most vehicles, and we sell most vehicles’ filters for between $20 and $30!

 

Replace your climate-controlled seat filter.

Does your vehicle have air conditioned or cooled seats? Most of these have filters that require regular replacement as well. Check your owner’s manual on how often you should tend to them on your vehicle.

 

Turn your fan speed down.

As tempting as it may be to really get that cold air blasting, you’ll usually achieve a colder vent temperature at settings around three quarters of the way up your blower motor’s fan speed range. For example, this may be speed #4 of 5 settings. The faster the incoming air is moving, the less time it spends inside your vehicle’s evaporator core to be cooled, and too much air can overload the system on hot days.

 

Use your “recirculate” or “max A/C” setting.

car ac not cold

In one pass through the system, your air conditioning system can only cool the incoming air by so many degrees. By switching to your “recirculate” setting, you direct the system to pull air from inside the vehicle (which has already been cooled once) instead of outside. This dramatically reduces vent temperature on most vehicles. Just be careful on longer drives, because the air conditioning system also dries the air that passes through it. You’ll want to switch off the recirculation mode from time to time in order to avoid dry mouth or headaches.

 

Check your radiator for restrictions.

radiator replacement

For your A/C system to cool properly, it must be able to draw large amounts of air through the condenser mounted behind your vehicle’s front grille. Dirt and mud build-up on the front of the radiator and between your vehicle’s various coolers – very common on trucks – can really reduce this airflow. We’ve even seen where a customer forgot their “Saskatchewan thermostat” (piece of cardboard) behind the radiator after the winter ended! While we’re taking shots at our neighbors to the east, radiators plugged with bugs and grasshoppers are a real cooling issue in the prairies as well! Most of this debris can be washed out with a garden hose from the rear of the radiator. Be careful using a pressure washer; you’ll want to keep the angle of your spray perpendicular to the radiator or else you’ll bend the fins.

 

Have your air conditioning system recharged.

While a perfectly sealed air conditioning system should never get low on refrigerant – or “freon”, as we used to call it – the reality is that over the years, the refrigerant level may drop. Removing, measuring and topping up (or “recharging”) the refrigerant level can get your vehicle cooling like new again. This is something that should be left to a professional; see our post here on why you should not use store-bought “canned” refrigerant products. If your air conditioning system becomes low on charge after just one year or two, then it likely has a leak that should be repaired.

We charge between $140 and $180 for this service, on most vehicles.

 

Have any air conditioning system problems or concerns? Email us or give us a call!