I was having a dickens of a time getting my car to idle well. Finally, I bought an inexpensive exhaust gas analyzer (EGA), which measures only carbon monoxide (CO) at the exhaust pipe. It cost me $140 plus 10 for shipping, but I justified the purchase of something to be used only rarely because it made sense as an alternative to giving a MB shop $150 to do something I could do.
There are a number of devices available that measure CO2, and other gases, as well as CO, but they cost over $3000.
The device worked well, I think, and now the car idles very well. The CO was around 8% when I started, and is now around 4%. The correct range is 3.5 - 4.5%, so I am in the middle. It probably took an hour and a half to do this the first time, including the 20 minutes or so required to allow the EGA to adjust to ambient conditions.
A brief tutorial on what I learned and did: Ambient air is usually about 2% CO. The EGA connects via long cables to the car's battery for power. It has a hose about a meter long with a metal tube at the end of the hose. This tube fits into the exhaust pipe, and is centered in the pipe by coil springs attached to the pipe at 90-degree angles. Before the car is started, the EGA is connected and allowed to sit for about 20 minutes. It has a digital readout, and once the reading has stabilized, an adjustment is made to the meter so it reads 2.0%.
Before connecting the EGA it is recommended that the car be driven hard for a few minutes to flush out things and reach operating temperature.
During the 20-minute wait for the EGA to stabilize, the engine will cool down a bit, but it will reach temp again during the testing.
The pipe is inserted into the exhaust pipe and the car is started. The reading will fluctuate for a minute or so, and then stabilize. At this point, adjustments to the screw at the rear of the injection pump and the air screw can be commenced. The use of an EGA for these adjustments is given in both the BBB and the Haynes manual.
The car has two exhaust pipes, of course, each servicing three cylinders. I adjusted the idle mixture for one pipe (to 4.0%) and then checked the other pipe. The reading there was 5.2%. This seems like a significant difference to me, and indicates a problem with fuel delivery to one or more of three cylinders.
I plan to drive the car awhile and then recheck and start to trouble shoot this problem. Now it runs very well, and I think my $150 was money well spent.
The EGA was made by Gunson (in England, I think), and I got it from a company in Florida selling them on ebay. Bought Friday night, shipped on Saturday, arrived on Monday.
I plan to use the EGA on multi-cylinder motorcycle tuning. They are apparently very useful for this.
Any comments on the above are welcomed.
Joe
