is this a bad ground????????

[blown1989saleen]

im having driveabilty problems after i did my battery relocation, immediatly AFTER my battery relocation my car started acting funny, 90% of the time the car runs fine, then the next thing you know it goes dead rich while cruising down the road, we're talking going from a A/F of 13.7 at cruise to 10.0-11.5.........at a cruise?? it also does this at idle too, then other times it will run lean, and then back to normal??? Pro-M recommends a 10ga ground directly from the battery NEG- up to the original ECU ground, could this be my culprit?


Thanks, Scott

 

[blown1989saleen]

TTT

 

[04sleeper]

I've had 3 cars with batteries in the trunk and a lot of my friends have them as well. I just run the ground to the rear of the car from the battery but I do add an extra ground strap from the block to the ECU ground. On my current setup I have a 1 Gauge wire ground running from my block to the ECU ground. On my last car I had a similar problem and I too read that tid-bit from PRO-M so I ran the extra peice of 10 gauge from the battery to the ECU ground and it still did not fix anything. I traced it to a bad ground in the Injector Harness. It was the ground for the Air Intake Temp sensor. I did not trace it all the way back to the computer so I just grounded it my self. Another thing that happened when it was not grounded was that my TP sensor would read 4.69 volts with the KOEO with the throttle closed and open. It did not change when you moved the throttle open. After I grounded the Air Intake Temp sensor the TP started to work again. I guess it is tied in with it.

I'm not sure if this will help or not with your problem but it is what I have experienced in the past.

 

[blown1989saleen]

I've had 3 cars with batteries in the trunk and a lot of my friends have them as well. I just run the ground to the rear of the car from the battery but I do add an extra ground strap from the block to the ECU ground. On my current setup I have a 1 Gauge wire ground running from my block to the ECU ground. On my last car I had a similar problem and I too read that tid-bit from PRO-M so I ran the extra peice of 10 gauge from the battery to the ECU ground and it still did not fix anything. I traced it to a bad ground in the Injector Harness. It was the ground for the Air Intake Temp sensor. I did not trace it all the way back to the computer so I just grounded it my self. Another thing that happened when it was not grounded was that my TP sensor would read 4.69 volts with the KOEO with the throttle closed and open. It did not change when you moved the throttle open. After I grounded the Air Intake Temp sensor the TP started to work again. I guess it is tied in with it.

I'm not sure if this will help or not with your problem but it is what I have experienced in the past.

Thanks it DOES help, gives me an idea of where to start looking.

Scott

 

[jrichker]

Here's some generic help with grounds...

Grounds are important to any electrical system, and especially to computers.

1.) The main power ground is from engine block to battery: it is the power ground for the starter & alternator.

2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.

3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. It uses a barrel type quick disconnect connector inline with the battery ground pigtail. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery.

4.) The engine mounted sensors have a common separate ground. This includes the TPS, ACT, EGR, & BAP/MAP. These sensors share a black/white ground wire that connects to computer pin 46.

5.) The O2 sensor heaters have their own ground (HEGO ground) coming from the computer. This is different and separate from the O2 sensor ground. It comes out of the fuel injector harness near the EGR valve.

6.) The TFI module has 2 grounds: one for the foil shield around the wires and another for the module itself.

7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer.

8.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally.

If you have access to a digital voltmeter and would like help diagnosing grounds, make another post and I will try to help.

 

[blown1989saleen]

Here's some generic help with grounds...

Grounds are important to any electrical system, and especially to computers.

1.) The main power ground is from engine block to battery: it is the power ground for the starter & alternator.

2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.

3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. It uses a barrel type quick disconnect connector inline with the battery ground pigtail. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery.

4.) The engine mounted sensors have a common separate ground. This includes the TPS, ACT, EGR, & BAP/MAP. These sensors share a black/white ground wire that connects to computer pin 46.

5.) The O2 sensor heaters have their own ground (HEGO ground) coming from the computer. This is different and separate from the O2 sensor ground. It comes out of the fuel injector harness near the EGR valve.

6.) The TFI module has 2 grounds: one for the foil shield around the wires and another for the module itself.

7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer.

8.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally.

If you have access to a digital voltmeter and would like help diagnosing grounds, make another post and I will try to help.

j you are the man, and this is this is the assistance ive waiting for i have a digital volt meter and im ready for ANY info you have.


Scott

 

[jrichker]

Voltage drop testing of grounds.

Use a DVM to measure the voltage drop across a connection or wire. Adding length to the test leads may be required, and does not affect the accuracy of the test. Use 18-20 gauge wire for the test leads if you have to lengthen them.
1.) Most grounds use the negative battery post as their starting point.
2.) The voltage will be small if the ground is good: less voltage drop = better connection.
3.) Be sure that the power to the circuit is on, and the circuit is being used in its normal manner. For instance, if it is a light circuit, the lights on that circuit should be powered on.
4.) To measure grounds, place one DVM lead on the battery negative post and the other on the wire or connector that goes to ground. Place the other DVM lead on the wire or connection you want to test.
5.) Read the voltage drop: Light duty circuits (1-5 amps) should show .1-.25 volts. Medium duty circuits (6-25 amps) should show .25-.5 volts. Heavy duty circuits (26 amps up) should show .5-.75 volt drop. A voltage drop lower that spec is always acceptable.

Now that you have the how to do it, start with the checklist previously posted.

 

[blown1989saleen]

Thanks J i'll post my results man.

Scott