Wednesday, May 22, 2019
Friday, May 10, 2019
Scheduled Maintenance: Normal or Severe?
If you have ever looked at your manufacturers maintenance schedule you may have noticed there is a "normal" service schedule and there is a "severe" service schedule. Most people figure they fall under normal service and follow that schedule. If you ever read the definition for severe service though, you may find your vehicle use falls into that category.
A 2002 Chevy Silverado for example has an odd way of determining which schedule to use. "Follow the NORMAL schedule only if none of the conditions from the SEVERE schedule apply." Italics are mine. (ONLY IF NONE). So, if ANY of the severe conditions apply to your vehicle use you should be using the severe schedule. Let's look at the "severe" conditions:
Follow the SEVERE schedule if any one of the following are true:
Most trips are less than 5 to 10 miles.
Most trips include extensive idling. (such as frequent driving in stop and go traffic)
The vehicle is operated in dusty areas frequently.
Trailer towing or using a carrier on top of the vehicle frequently.
The vehicle is used for delivery service, police, taxi or other commercial applications.
Remember, if any ONE condition is applicable to you then you are in the SEVERE condition schedule definitions. Interesting huh? I'm not sure what the differences are on the schedules themselves. Spark plug replacement isn't a huge difference. In fact, it is a little odd. Normal suggested spark plug replacement, 100,000 miles. Severe 99,000. ?? Thats weird. I would expect oil change to be different. Lets see. Replace oil at 3,000 under severe or 10,000 under normal. Huge difference there. Good time to note, oil change is not the same as oil check. Check your oil level occasionally between changes and if it needs oil, add oil. But never try to top off oil if it is less than a quart low. Wait for it to be a quart low, add a quart.
Moving on.
2008 Ford Escape. The Ford severe duty is called special operating conditions. Towing a trailer, using a camper or car top carrier. Extensive idling, low speed, commercial use (taxi, police, delivery). Operating in dusty conditions. Off road operation. Use of E85 50% of the time or more (flex fuel engines). I was curious about the spark plug change schedule here because I had one with 112,000 miles that the plugs were original and severely worn. Normal oil change intervals are at 7,500 and plugs at 90,000. Severe schedule is oil changes at 5,000 and plugs at 60,000. Ford says if you are operating at any of the severe duty conditions only rarely then you can stay on the NORMAL schedule. Good to know.
Let's jump it up a bit to a less older car. 2011 GMC Acadia. This was in recently also with original spark plugs at 180,000. I would say they don't pay much attention to scheduled maintenance but let's take a look. The service definitions are the same as for the 2002 Silverado. Normal schedule has oil changes at 7,500 and spark plugs at 100,000. Severe is oil at 3,000 and plugs at 100,000. No difference then as far as plug change. Only 80,000 miles past recommended replacement. No wonder it was misfiring.
Well that was some fun huh? Something to think about anyway. Have a good weekend!
Kenny@ggauto.repair
A 2002 Chevy Silverado for example has an odd way of determining which schedule to use. "Follow the NORMAL schedule only if none of the conditions from the SEVERE schedule apply." Italics are mine. (ONLY IF NONE). So, if ANY of the severe conditions apply to your vehicle use you should be using the severe schedule. Let's look at the "severe" conditions:
Follow the SEVERE schedule if any one of the following are true:
Most trips are less than 5 to 10 miles.
Most trips include extensive idling. (such as frequent driving in stop and go traffic)
The vehicle is operated in dusty areas frequently.
Trailer towing or using a carrier on top of the vehicle frequently.
The vehicle is used for delivery service, police, taxi or other commercial applications.
Remember, if any ONE condition is applicable to you then you are in the SEVERE condition schedule definitions. Interesting huh? I'm not sure what the differences are on the schedules themselves. Spark plug replacement isn't a huge difference. In fact, it is a little odd. Normal suggested spark plug replacement, 100,000 miles. Severe 99,000. ?? Thats weird. I would expect oil change to be different. Lets see. Replace oil at 3,000 under severe or 10,000 under normal. Huge difference there. Good time to note, oil change is not the same as oil check. Check your oil level occasionally between changes and if it needs oil, add oil. But never try to top off oil if it is less than a quart low. Wait for it to be a quart low, add a quart.
Moving on.
2008 Ford Escape. The Ford severe duty is called special operating conditions. Towing a trailer, using a camper or car top carrier. Extensive idling, low speed, commercial use (taxi, police, delivery). Operating in dusty conditions. Off road operation. Use of E85 50% of the time or more (flex fuel engines). I was curious about the spark plug change schedule here because I had one with 112,000 miles that the plugs were original and severely worn. Normal oil change intervals are at 7,500 and plugs at 90,000. Severe schedule is oil changes at 5,000 and plugs at 60,000. Ford says if you are operating at any of the severe duty conditions only rarely then you can stay on the NORMAL schedule. Good to know.
Let's jump it up a bit to a less older car. 2011 GMC Acadia. This was in recently also with original spark plugs at 180,000. I would say they don't pay much attention to scheduled maintenance but let's take a look. The service definitions are the same as for the 2002 Silverado. Normal schedule has oil changes at 7,500 and spark plugs at 100,000. Severe is oil at 3,000 and plugs at 100,000. No difference then as far as plug change. Only 80,000 miles past recommended replacement. No wonder it was misfiring.
Well that was some fun huh? Something to think about anyway. Have a good weekend!
Kenny@ggauto.repair
Thursday, May 9, 2019
Lean Codes: 2002 Silverado
2002 Chevrolet Silverado 5.3 vin T comes in with MIL on and lean codes for both banks. Complaint is that the engine doesn't run well.
Other than codes stored I don't see a problem. The truck seems to run fine other than an occasional sputter at idle.
Lean conditions can be either caused by too much air in the mix (vacuum leak) or not enough fuel (fuel delivery). Next step is to determine which is the case. If the system goes lean at high fuel demand then the problem is with fuel delivery. Easiest way to determine a problem there is to drive the truck at road speed and accelerate hard. Notice if the truck loses power and record O2 activity. In this case the truck had great acceleration and O2 for both banks showed plenty of fuel in the mix under high demand.
The other side of the coin would be a vacuum leak. A vacuum leak would drive the mix lean at low rpm, low demand and at the present time, with the warm engine. I wasn't seeing a problem there either.
The thing is though, I happen to know these engines have a common problem with intake manifold gaskets allowing vacuum leaks when the engine is cold and sealing once the engine is warm. I could let the truck sit overnight and look for vacuum leaks on the cold engine. Usually you can monitor short term fuel trim while spraying carb cleaner at the manifold base and if the spray gets pulled in the fuel trim will drop dramatically.
There is another option though. Freeze frame data is stored when a code sets and captures data that was present at the time. So if we look at freeze frame and see a cold engine, low load and low rpm that means vacuum leak. It would also indicate the vacuum leak was the intake gasket problem.
That is enough evidence to warrant removing the intake manifold. Definitely bad intake gaskets.
Hopefully this will also help with the poor running complaint. At any rate, the vacuum leak is fixed.
Thanks!
Kenny@ggauto.repair
Lean conditions can be either caused by too much air in the mix (vacuum leak) or not enough fuel (fuel delivery). Next step is to determine which is the case. If the system goes lean at high fuel demand then the problem is with fuel delivery. Easiest way to determine a problem there is to drive the truck at road speed and accelerate hard. Notice if the truck loses power and record O2 activity. In this case the truck had great acceleration and O2 for both banks showed plenty of fuel in the mix under high demand.
The other side of the coin would be a vacuum leak. A vacuum leak would drive the mix lean at low rpm, low demand and at the present time, with the warm engine. I wasn't seeing a problem there either.
The thing is though, I happen to know these engines have a common problem with intake manifold gaskets allowing vacuum leaks when the engine is cold and sealing once the engine is warm. I could let the truck sit overnight and look for vacuum leaks on the cold engine. Usually you can monitor short term fuel trim while spraying carb cleaner at the manifold base and if the spray gets pulled in the fuel trim will drop dramatically.
There is another option though. Freeze frame data is stored when a code sets and captures data that was present at the time. So if we look at freeze frame and see a cold engine, low load and low rpm that means vacuum leak. It would also indicate the vacuum leak was the intake gasket problem.
That is enough evidence to warrant removing the intake manifold. Definitely bad intake gaskets.
Hopefully this will also help with the poor running complaint. At any rate, the vacuum leak is fixed.
Thanks!
Kenny@ggauto.repair
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