Solving Automotive Performance Issues
This is defiantly old school but as I’ve stated over and over in this article modern engines function in the same way they always have. Your engine is an air compressor. When it’s working correctly, it’s smooth and wonderful. If it’s not working correctly it can cause performance issues. A vacuum gauge is an inexpensive tool that can tell you quite a bit about how your engine is performing. If you hook a vacuum gauge up to an intake vacuum source, it can tell you a lot about your engine’s health. On a good running engine you should see engine vacuum between 17-21inhg at idle. The needle should hold steady and not shake about. If it’s low or shakes, then you have a performance issue somewhere. I don’t want to get into all the specifics of what problems are indicated by the vacuum readings you get, but I do want to make you aware of this tool and it’s capabilities. Even if you just hooked up the gauge and observed the reading you would have a pretty good idea of how your engine is performing. At some point I may do an article just on using a vacuum gauge. For now you can use this next test to see if you have and exhaust restriction. It’s a pretty cool test, I think you’ll like it.
As long as we’re on the topic of engine mechanicals, let’s talk about the effects of a restricted exhaust. Imagine being able to breathe in but not out. It wouldn’t be long before you pass out cold. The same thing can happen to your engine. If you have a restricted exhaust due to a catalytic converter failure, damage to the pipes themselves, or a restricted muffler, your engine will be sluggish and underpowered. Surprisingly, testing for this isn’t that difficult. All you need is a trusty vacuum gauge. To use a vacuum gauge to find an exhaust restriction, you first need to find a place on your intake where you can hook the gauge up. You’re looking for an intake vacuum source. This would be a source that has high vacuum at idle. Look for a line connecting somewhere after the throttle body. Pull it off while the engine is running. If you feel vacuum there, that’s where you want to hook up. On a good-running engine, intake vacuum should be between 17 to 21 INHG. (That’s inches of mercury for those of you who are curious.) Vacuum is also measured in Bar, but for this article we’re going to use INHG.
The needle on the gauges should also hold steady and not bounce around. If it does, this might indicate a mechanical issue with the engine. Also, intake vacuum is highest at idle and drops off to zero the closer you get to wide open throttle (WOT). With the engine running, take your first reading. Raise the RPM to about 2000 or 2500 and watch the gauge. If you have an exhaust restriction, you’ll begin to notice that vacuum will slowly drop off over time, and it might be harder to maintain the RPM. If the vacuum remains the same, then you don’t have a restriction and you can move on to other tests. Here’s a video showing the test in action.
If you suspect your catalytic converter is bad, or you have a P0420, there is an easy test to check your catalytic converter’s operation. You first need to get your hands on an infrared thermometer or a thermocouple. Basically, you need something that can accurately measure temperatures up to 1,200º F.
When a catalytic converter is working properly, it will be 100º F hotter at the outlet than it is at the inlet. First, make sure the engine is up to operating temperature. Then run the engine at about 2,000 to 2,500 RPM. Take the temperature readings at the front and rear of the catalytic converter. You should see an outlet temp that’s 100º F hotter than the inlet temp. If you don’t, the catalytic converter is bad and should be replaced.
I’ve heard that you can sometimes repair a bad converter, but I have yet to try any of those methods. Jury’s still out on that one. I mention this because catalytic converters are often quite expensive. That’s because they contain platinum, and platinum in their substrate. These are precious metals and are expensive. The expense of a new converter often holds people back from repairing the issue. If you live in a place where there is emissions testing, you will have to deal with it at some point.
I’m going to once again touch on aftermarket parts here. There are some universal catalytic converters out there that you can use as a replacement. Know that sometimes these won’t work and will still set a P0420 right out of the box. So if you’re faced with having to replace your catalytic converter, be sure to use a quality part for best results, OE (Original Equipment) if you can afford it. Here’s a video demonstrating the converter test.
Video Title: Solving Automotive Idle Problems – EricTheCarGuy Video Description: In this Article, Solving Automotive Performance Issues, Eric looks at what can be the cause of Solving Automotive Performance Issues with your vehicle .Thumbnail: http://www.ericthecarguy.com/images/faq_buttons/Large_FAQ_Images/Performance-and-Driveability-icon-large.png