Question on "Gunson's Gas Tester"

[Scott R]

I just purchased this unit:



Now my question is before I use it today is, won't the plastic hose melt form the exhaust heat?

And secondly, should I remove the spring barb on the end of the metal sniffer?

[grant lyon]

The coil springs help keep the tube in the muffler. The kink on the other end of the metal tube rests on the lip (exit) of your tail pipe -- so enough of the metal tube plus clear flex tube is out of the hot exhaust stream to keep the clear tube from getting too hot. You may want to leave even less of the metal pipe stuffed up into the tailpipe/muffler if the clear tube still gets too hot and starts falling off.

Take your time getting a good null calibration (warm unit, no exhaust fumes anywhere near).

[RarlyL8]

The plastic tube will melt if you push the aluminum tube in too far. The aluminum tube needs to go about 1/2 its length up the tail pipe.

The spring barb keeps the tube in place while testing. Try it out on your car with the engine off and the exhaust cold. You'll see how it works.

One word of advice - these testers require at least 15 minutes minimum to acheive a stable base line. I hook the meter up to another car battery and let it equilibrate for a good 30 minutes. In the mean time you can get the 911 fully warmed up. Be sure the Gunson is NOT in the wind. Pull the car DOWNWIND of the Gunson and plug in the sniffer. Do not allow the cars exhaust gas or cooling heat to blow on the Gunson, you will pollute the baseline reference. It will give you a good stable idle CO reading in a few seconds. Pull the sniffer out and let it return to baseline. It may take a minute or two. If the Gunson does not return to 2.0% CO baseline you need to repeat the process - the baseline either was not steady or the reference gas/air became polluted.
These are good little units, you just need to understand how they work to help them do their best.

[Scott R]

Guys, I thought it was supposed to be inserted into the test port before the cat, that's why I questioned the barb.

[RoninLB]

mine takes a long time to warm up. I use a spare battery to power it while I warm up the car and still keep it on the spare for testing. I also used a longer tube to give me room to move the unit away from the exhaust.

[rrsrsr]

Yep- with a CAT equipped car you need to adjust the mixture by measuring at the test port.

I think the aluminum tube is too big. You may need a narrower diameter tube, or you could remove the O2 sensor & use that opening (I think the manual tells you to disconnect the O2 sensor to tune anyway)

[Scott R]

Originally posted by rrsrsr
Yep- with a CAT equipped car you need to adjust the mixture by measuring at the test port.

I think the aluminum tube is too big. You may need a narrower diameter tube, or you could remove the O2 sensor & use that opening (I think the manual tells you to disconnect the O2 sensor to tune anyway)

I'll try that, last time I pulled an O2 sensor it was on my 951, and it almost resulted in me losing a finger. Man those suckers are in their tight.

[Scott R]

Ok, just got done and what can I say, this thing is one great tool! I parked the mixture right on .06 and it's running like a top! Thanks for the 02 sensor removal suggestion, that did the trick!