Ok, yesterday, I decided to go out and check my TPS voltage to verify the correct voltage range. The TPS checked out perfect. But while I had my multimeter out, I decided to play a little.

Well anyway, I started the car, then decided to place the negative electrode from the multimeter on the upper intake manifold. I then placed the positive electrode on the Chassis. To my amazement It read .06 volts. I reversed the electrodes and got a -.06 reading. I then tested other parts, such as the exhaust and alternator with readings nearing .1 volt.

Could this be bad grounding???

If it turns out to be grounding, perhaps a multimeter would be an excellent tool to determine where grounds are needed.

 

OH YEAH, I wanted to see if someone could go test there car and post there readings too. Just to compare.

 

I had tested the DP where I have O2 sensor. Its as high as .02
And I have an extra ground wire on the dp to chassis.

 

Was it a paintless part of the chassis?

Dave

 

I wouldn't call that a bad ground...I call it a leak somewhere.

 

Yeah, Well I touched it to a painted surface as well as bare metal, and boltheads. Anywhichway, I got pretty much the same reading.

Also, I tested my alternator, all 3 wires attached to the alternator and got 12+ volts for each one (pretty much the exact same reading out of each wire).

 

Any Idea where this could be coming from? Perhaps a hot wire somewhere touching the chassis?

Could this be affecting the way my car runs? Because sometimes my car runs good, sometimes it runs bad. Seems like an electrical problem to me. My instincts (not that they have ever been right) tell me it is something with the ignition system.

Does anyone know if I can use a multimeter to test my plug wires, coils ect??????

::praying:: God, please, I just want my car to run right

 

Could it be electrical noise from the ignition system? I work on manufacturing equipment everyday and .1v could just be the variance within your meter. Has it been calibrated? Yes you can test your wires and coils with a meter.. The wires should be easy as long as you don't have an intermittent problem. As for the coils.. I don't know.

 

You are reading the difference in voltage between the two locations. This test can be used to find bad grounds on your car. Measure voltage between the negative terminal of your battery and different parts of your car (engine, chassis, etc...) any voltage higher than .5 volts can be a sign of a bad ground. Here is a site that explains voltage drop testing...

http://www.autosite.com/garage/encyclop/ency12b.asp

Joel

 

I wouldn't worry about that too much, just yet.

The alternator sends current out to everything, much of the the current returns through various chassis grounds, through the chassis, then that same current returns through the body-to-engine connections to return back to the alternator. You're basically measuring the voltage drop across the resistance of these cables.

The cables face engine heat which will raise their resistance. (The exhaust connections are even worse.) You can help fight this by adding more engine--chassis grounds, but they can be unnecessary.

Look at it this way, if you're pushing 10A through those cables (which is an extremely optimisic [low] estimate), and you're seeing .06V, then the combined DC resistance is .006 ohms. That's pretty damn low, and that's a "high" estimate.

You might be able to lower this number by adding grounds. But in the end, that particular voltage differential probably wont make any difference to the systems function. However, if you have an intermittant bad ground that appears only when the vehicle is in motion (that you're obviously not picking up yet, with this test), an extra ground may mask the problem.

You'll likely see this number jump up when you turn your lights, AC fans, stereo, etc. on. This is a valid troubleshooting test, but I'd only be concerned if I saw volt or two while "fully loading" the alternator.

 

Hmm... a lot of what I said appears in ljrotary's link. I'm still to lazy to read all of it though. :P

 

the coolant voltage is another. put the lead in the filler neck not touching the sides. run the car and see what effect the different electrical loads have on the voltages.

 

Sounds about right to me.

 

Thanks for the info everyone, It is always helpful, I guess I will just look elsewhere for this little demon that lurks in the shadows of my rx7.

I am thinking of selling this bitch and getting an evo MR in september. I am scared to ask what you guys would think about that.

 

fc1jz, I ment "mask the problem" in a beneficial sense. Adding a ground may actually help alleviate an intermittant problem caused by a shotty stock ground.

It just that you probably wont detect an intermittant ground fault (the kind that like to appear when you go over bumps, when the engine is rocking under power, during sweeping turns, etc.), when the car's idling and you're standing over the engine compartment with a volt meter.

 

Before you go chasing demons in your car, you should verify that your meter is actually reading 0 volts. This can be done by simply touching the two probes together. When you do so, if the meter reads the same as what you were reading between the UIM and chassis, then there is no problem. Usually you will see a small difference depending on the quality of the ground, but the less the better.

Also, was your meter set to AC or DC volts?

 

I have thought about getting one, but all the talk about them voiding warranties if the car gets near even an Auto X track, rod failure, and the uncertainty of Mitsu's future is a little disturbing.

 

He got symmetrical results when he reversed the probes == no cabration issue worth worrying about.

I'd assume he used DC, since meters do not read negative AC values... unless he used a o'scope

 

Definitely reads zero probe to probe. The multitester is dead on. There is definitely a voltage difference between the UIM and Chassis. However, it seems it is too little to really worry about. Since we are only talking about 1/20th of a volt.

 

Mitsubishi claims the bugs have been worked out of the motor in 05. So hopefully no rod failure, and they already fixed the crankwalk problem. As well, my warranty will be voided very quickly after the install of a few mods

And the uncertainty of Mitsubishi's future is the reason this 45k car is selling for 33k. I have seen tests where the MR is in the 12's factory and can pull nearly 1g on the skidpad. That is a damn race car. Plus if they went out of business, I would own there last supercars.

All for a little more than an rx8???? Im lovin it.

 

a little off topic but did you guys know Mitsu has created web crawlers that are going out to all of the regional scca websites that show local scores, ect and also to known mits forums and gaining info about people racing new mits cars and doing research to find out who they are and voiding thier warrenty. Even if the car is bone stock? Most of what I heard came from the scca ranking cause that is regional so they know where the person is, they have thier car description and thier full name. They are logging all of that info and tracking that in a data base that is looking for names for warrenty work being done. That is absolutly crazy

STEPHEN

 

Just the opposite of Nissan with their track model 350Z. They ask NO questions if you bring it in. Had a friend with a transmission failure (from track day stuff, although there was a known issue w/the gearbox) and Nissan replaced the box, no questions asked.

 

Just another reason not to buy a nissan

:EDIT: Sorry, I just hate nissan. Every experience with nissan automobiles or employees has sucked a couple of hairy ones.