TPS Voltage Drop when Accessories are on.

[supraguy31]

Hey all.....

Its been a while since I posted anything and Im at the end of the Straw on this one. Could use a little Insight here as to this Problem.

Basic Mods.

Ron R FFIM
Q45 Throttle Body and TPS
GT4067R Turbo
MAFT Pro
etc etc etc

Start car and Watch MAFT Pro TPS voltage, Once warm it Settles between .38 and .40v, At this time I can drive the call all day and not have any Issues what so ever...

Problem........ As soon as I turn on the Headlights, Fog Lights or even use my turn Signal the TPS voltage drops to .15v and sometimes even to .00v and the A/F start to go crazy. Jumps from 11.0 to 17.0 and will not settle back down. Car starts to sputter and Hesitate at cruising during this time.

Now as soon as I turn the Headlights off everything goes back to normal after about 30 Seconds and TPS voltage goes have to the normal range.

Anyone have any recommendation on what I can or should be looking for.

Thank you
Robert

 

[whitemike]

That's pretty odd. I'm curious to see what the experts say here. Have you checked your grounds? Battery to chassis?

 

[supraguy31]

Over and over again.

Battery is in the Trunk and Grounded Properly
Harness is grounded under the Intake Manifold as it would usually be on the Stock Configuration.

 

[whitemike]

Over and over again.

Battery is in the Trunk and Grounded Properly
Harness is grounded under the Intake Manifold as it would usually be on the Stock Configuration.

"Grounded properly" - you're running a 2ga wire to the front? Or you're grounding to the chassis?

 

[supraguy31]

Running the Short (2 foot) 2 guage cable from the battery Negative post to a Bolt that is screwed into the frame of the car in the trunk. Only thing I dont have is that small Extra ground that most cars have that screws into the side of the firewall area like the stock configuration has. If I do indeed need that then I can run another ground wire from that post to another spot.

 

[whitemike]

Running the Short (2 foot) 2 guage cable from the battery Negative post to a Bolt that is screwed into the frame of the car in the trunk. Only thing I dont have is that small Extra ground that most cars have that screws into the side of the firewall area like the stock configuration has. If I do indeed need that then I can run another ground wire from that post to another spot.

There's a ton of resistance in the path from the trunk area to the engine bay. I would definitely recommend you run a 2nd wire for the negative back up to the engine bay..

 

[Nick M]

What is the battery voltage when you turn on those accesories? Do you have code 51?

 

[mkiiichip]

There's a ton of resistance in the path from the trunk area to the engine bay. I would definitely recommend you run a 2nd wire for the negative back up to the engine bay..

I have read allot of conflicting info on this^
So this is what can happen?
Cant you do a voltage drop test, between the battery and motor, to verify?

I am interested to see how this pans out.

 

[supraguy31]

I will do a Voltage check tomorrow.

I do know that when I turn the Headlights on the Alternator gauge on the Instrument cluster drops and if I turn the Turns Signals on everytime it blinks the Instrument cluster needed bounces with it.

Robert

 

[whitemike]

I have read allot of conflicting info on this^
So this is what can happen?
Cant you do a voltage drop test, between the battery and motor, to verify?

I am interested to see how this pans out.

I can't tell if you're being a dick or if you're genuinely concerned.

All of the info I've read was SME's and mods telling people not to just ground the battery in the trunk area and call it a day. Do a google search for "battery relocation site:supramania.com"

-Mike

 

[jetjock]

I don't think he's being either. It appears he is simply trying to understand the difference between what will work, what is correct, and whether the OP's problem is related to the matter. At least that's the way I see it...

 

[whitemike]

I don't think he's being either. It appears he is simply trying to understand the difference between what will work, what is correct, and whether the OP's problem is related to the matter. At least that's the way I see it...

I see, well I elaborated on what I meant without an attitude or sarcasm just in-case I was wrong about what he meant

Although I don't feel him grounding the battery in the trunk area is directly related to the issue, I definitely think It's a major weakness in his electrical system. You being the electronics whiz you are, please feel free to comment. I actually moved my battery a week ago which is why I spoke up about it, I did quite a bit of searching on the forums before I took any action on my own car.

Just trying to help a fellow member, not spread misinformation, as always - correct me if I'm wrong.

Thanks

 

[mkiiichip]

I am actually interested, as i have to relocate my battery before it gets intercooler pipes, and becomes roadworthy. Just looking for some solid information.

There are a couple write-ups here that include grounding the battery in the trunk, and no issues mentioned. Only theory posts are mentioned (ie resistance between the subframes, body, and motor). And all kits only have a short ground cable. Is that only for old-school solid frame cars and trucks?

Also, if you run a ground cable all the way to the motor, and have a smaller gauge ground strap at the battery, to the body, does that create ground loops?

 

[supraguy31]

Ok so Let me make sure I know what I need to go and Verify here.

Check to see what the Difference is in Voltage when the Headlights are on and off?

Also, I think I understand where you all are coming from when you talk about grounding the battery but Im wondering what does it matter as long as its a Solid ground. Does it have something to do with the Negative cable being grounded to the Engine Block or Motor Mount bolts as Ive seen some that way.

Should I remove the Short ground cable and install a cable all the way back up too the original location ie.... engine motor mount or engine itself?

Thank for all you guys help.
Robert

 

[mkiiichip]

To verify that the ground path is the issue, test with the headlights on and off. Take a volt meter and put one lead on the battery negative terminal, the other at the engine block (likely need some extra long leads). The reading you are going to get is a difference in voltage between the battery and engine. readings should be almost 0. Any reading above 0 indicates that it takes voltage to push current to ground, indicating an issue.

 

[supraguy31]

Ok so where is the Diagnosis so far.

Car running with Headlights off Im getting 14.47v from the battery positive to the Ground Point of the Negative cable.
Car running with Headlights on, Im getting 13.5v consistant from the battery positive to the ground point of the negative cable.

Will update you in a sec on mkiiichips method.

So I just did the Above Method ....

One Lead to the Negative terminal, One Extended Lead to the Engine Block with Headlights off Im getting a Consistant .20v
Same setup but with Headlights on.... It showed .33v and Increased slowly up to .45 to .47v and leveled off there.

Now Once the A/F starts to jump around as the TPS voltage changed as said in First post, the Voltage started to jump around from .30 to .45v and would not level off any at all from this point.

So with this said, Do I need to redue my Negative grounding calbe and run it up to the engine? or should I just take an Extra ground wire and run it up to the Engine bay and ground it to the Engine block?

 

[Nick M]

You can start with a thourough exam of the factory negative battery cable.

 

[supraguy31]

You can start with a thourough exam of the factory negative battery cable.

Its not a factory Negative battery cable. This is a 2 guage Black cable that came with my Battery relocation kit. Maybe its the location that I have it grounded but It seems be be grounded fine. Bolt that screws into the frame inside of the trunk of the car. Very tight fit.

 

[carfreek]

Robert, I would do a cable from current battery ground to block ground, then one from block ground to fender/fender apron ground point. Id also put one from ECU manifold ground to where firewall ground strap bolts to head. If you arent already, Id put Maft-Pro ground on intake with ECU ground. MKIIs seem to respond well to correct/extra grounding, maybe its an age/metallurgical thang?

 

[CajunKenny]

Power Drop:
What's the condition of your alternator?

Grounding:
Was the bolt you used in the trunk painted? If so, remove the bolt and use a wire brush (or similar) to remove any and all paint from the entire bolt. Also, make sure that the threads and/or hole are paint free as well. Basically, you want metal on metal... Additionally, some di-electric grease is a good thing to use to help with conductivity and to reduce rust/corrosion.

Running a second ground up to the engine bay will not create a ground loop. It will provide additional grounding. Attempt mimic the stock setup.