damn i cant win car broke down need help


New Member
Mar 25, 2006
oswego Il
drove my car last night and shut it off. then i got back in it and it cranks and starts but sonn as hit the gas the rpms drops and dies. my tps sensor wont back down its at 4.86 i exposed the wires to adjust it and it wont adjust it stays at 4.86 i tried a different multi meter same reading i got rid of the egr valve and block the holes in the throttle body. i have new wires plugs cap rotor could my coil be bad. i would start it so much that that the battery wouldnt turn the motor so i let it be for 15 min and it would start. now if i drain the battery so much why would it crank fine 10 min laters. im confused
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StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
Dublin GA
Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

If you cannot dump the codes, you definitely have a signal ground fault.

A fault in the TPS circuit where the voltage goes above. 4.3 volts at idle can shut off the injectors.

TPS adjustment:
Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

Always use the Dark green/lt green & Black/white wires to set the TPS base voltage.

Do the test with the ignition switch in the Run position without the engine running.

Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts
source from the computer.

Adjusting the TPS fails to resolve the problem:
If the adjustment does not work to get the voltage below 1 volt, you probably have a
bad signal ground. The black/white wire is computer pin 46 and is signal ground for many things. If it
burns up inside the computer you get multiple faults and cannot pull codes..

Check the black/white wire resistance. Connect one ohmmeter lead to the black/white
wire on the TPS and one lead to the negative post on the battery. You should see less
than 1.5 ohm, more than that indicates a problem. Always take resistance measurements
with the circuit powered off.

Clean the 10 pin salt & pepper shaker connectors.

How it is supposed to work:
The black/white wire (computer pin 46) is signal ground for the computer. It provides a dedicated
ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the
computer into self test mode. Since it is a dedicated ground, it passes through the computer
on its way to the computer main power ground that terminates at the battery pigtail ground.
It should read less than 1.5 ohms when measured from anyplace on the engine harness with
the battery pigtail ground as the other reference point for the ohmmeter probe. What sometimes
happens is that it gets jumpered to power which either burns up the wiring or burns the trace
off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60. Only an
experienced electronics technician can open the computer up & repair the trace if it burns
up and creates an open circuit.

How to test the wiring :
With the power off, measure the resistance between the computer test ground
(black/white wire) on the self test connector and battery ground. You should see less than
1.5 ohms.

If that check fails, remove the passenger side kick panel and disconnect the computer
connector. There is a 10 MM bolt that holds it in place. Measure the resistance between
the black/white wire and pin 46: it should be less than 1.5 ohms. More that 1.5 ohms is a
wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the
computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than
1.5 ohms. More that that and the computer’s internal ground has failed, and the computer
needs to be replaced.

Measure the resistance between the black/white wire on each of the following sensors: TPS,
ECT, ACT and EGR. If you find one that is greater than 1.5 ohms, measure between that sensor and pin #1 of the white 10 pin connectors. Pin #1 is the center pin and is labeled sig-rtrn on the diagram