Why did this happen?
 

As I've indicated in previous posts, my car has been running badly lately... rough idle, surging under acceleration etc. The ultimate cause of the problem was this:

I have an aftermarket gauge pod. In the pod is a transmission temp gauge, and an Air:Fuel Ratio gauge. The ground wire for the gauge pod came off the ground. With the ground wire for the guage pod off, the car runs bad. When i touch the wire to a ground, the car immediatly starts running fine.

Why? It doesnt make any sense.

Mike

Not sure since I don't know your hook-up, but I suspect the air/fuel ratio gauge is disrupting the sensor input to the ECU if it's not grounded. I believe they take their data off the O2 sensor lines.

That's correct, Lee. I had it pulling the signal from the right side O2 Sensor.

Mike

OK, I don't know the specifics of your gauge, here's what autometer has to say
 

keep in mind that the O2 sensor only generates anywhere from 0-1 volt, and averages around .5 volts. A poor or deteriorating electrical connection is not only frustrating but could also prevent this small voltage from reaching the computer and the gauge, too. Always be sure to check the electrical connections as well.

Testing the O2 sensor output is another way to ensure proper operation. A digital voltmeter can be used to test the output of an O2 sensor. WARNING! Be sure to only use a high impedance digital multimeter to measure the O2 sensor voltages. A conventional analog or low resistance meter can draw too much current and potentially damage the sensor itself. So, for testing, be sure to warm the engine to full operating temperature to shift the computer into closed loop. The sensor must be hot(at least 600 degrees or hotter) to operate properly. You may have to warm the engine at fast idle for 5-10 minutes with some cars to reach the target temp. Note that a few systems can drop out of closed loop at idle, so you may have trouble keeping the engine at a hot enough temp to see the readings you are looking for.

Just to reiterate, we STRONGLY recommend that when you make termination to the A/F ratio input wire on your vehicle that you solder the wires together, so that the connection is permanent, and also there is no potential for wire breakage or contamination of the signal transfer. PLEASE also be sure to test the signal wire BEFORE you solder the wires together, by twisting the wiring together; this will work for testing to ensure proper connection prior to the final termination.

It seems you were able to detect that your car wasn't running well without the help of that gauge. In fact, that gauge caused you a problem. There seems to be a pattern developing here... ;)

Molecules of O2 passing through/by the sensor create a small voltage, less than 1v. Just about anything you connect to that output can alter it, even if only slightly. That in itself could be enough to cause three cylinders to not operate optimally. Your call, is the gauge worth it?

Well, the gauge wasnt the problem... When the gauge is connected properly, all is well. When the gauges ground is removed, the car runs poorly. It was my fault for not soldering the connections. :)

Mike

Beav,
 

Please don't think I'm challenging you because I have the utmost respect....

I don't have an air/fuel gauge - don't intend one - and I suppose one should really have two for the SVX . However, I've been told by devotees that the gauge behavior can foretell a dying 02 sensor by sluggish meter movement. Also it is a method of telling other things from rich/lean mixtures indication. Examples I was given (but can't judge for validity) include failing fuel filters (lean), potential for catalytic converter damage, etc. So, if these folks are right, it could be an indicator for those with less knowledge and skills than I believe you posess. Of course a failing gauge can screw things up too (as this thread shows).

So my question would be if you see any benefit to the various gauges (air fuel, volt-meter, tranny temp, etc) for people of lesser skills, or do you think I'd be better off just trusting to the seat-of-pants/know-your-own-car diagnostic tool? I ask because I keep debating with myself about installing a tranny temp gauge.

thanks

I got mine cause it looks neat! :D

Mike

Mike Davis
 

easily amused by bright, shiny objects!:D :p

Todd

mmmm... shiny...

Re: Beav,
 

Tranny temp guage provides info that gives insight about our driving habits,
helpfull when one wants to prolong tranny life...

I know a lot of truckers that refuse to buy a Peterbilt just because they put a gauge on everything. The problem, as they see it, is a loose wire, bad sending unit, etc. can sideline a truck. And as we all know, if it ain't runnin', it ain't making payment money...

As I've said many times before, people do this stuff for their own reasons and I really don't care one way or the other. You can put a flashing light on some plastic dog poop and find a whole new market. You see, it all comes down to perceived value. Millions of cars on the road and the vast, vast majority don't have such a gauge, yet for the most part, they do just fine without one. This one was ... an enhancement. It caused a problem. Instantly the 'benefit' was usurped. It turned out the product wasn't at fault, but it wouldn't have been a problem if wasn't there at all.

Mike - by all means, have at it. My initial response was just a little poke in the ribs - nothing more. And by all means, whip out that soldering iron. :)

Lee - no problemo. Nobody has to walk on eggs around me. As far as the benefit of that particular gauge it might signal something, if you're adept at understanding how to interpret the readings. If it were to suddenly start reading low (or high) that in itself doesn't indicate a bad EGO sensor. It could be a bad MAF, a vacuum hose off, etc. - but these are all things that we would feel anyway. CATs don't melt from lean mixtures, only from rich and that can easily be smelled.

For me, at least, extra guages=more paranoia. I'll stick with the stock system. If the tranny's going to go out, I'd rather it just do it. Generally, if I've done all I can do, otherwise (filter, cooler, synth [although, I don't do synth]), the sucker's gonna die and there ain't a darned thing I can do but worry about it 'til it deteriorates. I'd like those few extra miles of blissful ignorance before my blood pressure peaks. Drive on brave warriors, drive on! :D:D:D

I'll pass that information on to my Dad. He is Director of all North American sales for Peterbilt.

Peterbilt's are awesome trucks, if I had the opportunity, I would drive one all the time! :D My brother's and I had the chance to name their newest truck (397 i think), none of the names stuck though :mad: .

I've never seen inside a Peterbilt, but, a friend of mine had a pair of K-Whopper conventionals that were plusher than most folk's homes.