Losing my mind with electrical issues.

Mar 26, 2022
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I've finally got my car to start, idle, and apparently only drive in reverse. My 2002 GT Convertible is having some issues. The car starts, idles, revs, and reverses like a normal car should. It has no CEL, alternator is new and tests good, but for some reason when you put it in first gear and release the clutch the gauges go crazy and it falls flat on its face. I can literally drive all day long in reverse and give it all the skinny pedal with zero issues, but once I let out of the clutch in a forward gear she runs like absolute garbage. I've been searching for grounds, but my Haynes manual only tells me so much. Where are my ground locations? I know of the one from the motor mount to the battery, the one from the motor mount to the chassis, and the one that runs from the core support to the battery. Other than that when it comes to grounds, I'm as lost as morals in a meth lab. Please help, I need some 3 pedal therapy and a dump truck isn't cutting it. Also I just put a new starter in, at the tabs that run along the wire loom grounding? I had been told they were.
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Mar 26, 2022
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It doesn't want to move at all? Any bucking or engine surge?
It moves, bucks, and runs like dookie. If you ease out of the clutch really slow, and give it very light throttle you can get to second gear on flat ground. You give it 1/4 or more throttle then it kills out. I've been told loose ground, and also bad motor mount causing wires to get pulled. Also was maybe thinking its toward the passenger side wiring because of the BCM thinking that may be the crazy gauge issue. Trying to see if anyone else has been through the same thing.
 

COramprat

...I can take it. I think.
Mod Dude
Mar 2, 2003
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I'm wondering if its related to the transmission. It revs and idles in neutral, does fine in reverse but acts up in gear. I can't be sure but maybe a transmission speed sensor? Check the connection and make sure the wiring is good.
 
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weendoggy

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Jan 14, 2019
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I'm wondering if its related to the transmission. It revs and idles in neutral, does fine in reverse but acts up in gear. I can't be sure but maybe a transmission speed sensor? Check the connection and make sure the wiring is good.
Kinda' what I was thinking on the VSC sensor. That's the only thing connected to the ECU from a manual trans. The sensor feeds the signal to the ECU then dash so maybe that's what's making everything silly. Not sure, but easy to find out. I've been perusing my '02 wiring manual.
 
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Mar 26, 2022
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Kinda' what I was thinking on the VSC sensor. That's the only thing connected to the ECU from a manual trans. The sensor feeds the signal to the ECU then dash so maybe that's what's making everything silly. Not sure, but easy to find out. I've been perusing my '02 wiring manual.
I didn't even think there were electronics on the TR3650 besides for the speedometer.
 

COramprat

...I can take it. I think.
Mod Dude
Mar 2, 2003
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I
I didn't even think there were electronics on the TR3650 besides for the speedometer.
If I remember correctly that's what is does. Sends a signal for the speedometer but if it has a bad connection it could be throwing off the reading... possibly shorting out. I had a similar situation when I had nicked the wire to an O2 sensor. The car would randomly shut down until one day it shorted out and kept blowing the PCM fuse. I decided to check the sensor since that was the last thing I worked on and the it was. The bare wire was touching the tray the O2 connector was mounted to.
 
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weendoggy

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Jan 14, 2019
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I didn't even think there were electronics on the TR3650 besides for the speedometer.
Yep, that's the only one directly connected to the 3650, but it's in the loom with the O2 sensors as well. I'd be checking out that aspect of the wiring. Funny it drives in R which leads me to the OSS due to the fact the speedo doesn't work in R.

Pin 84 at PCM is feed from pin 2 of the OSS and pin 1 of OSS is signal return at 91 of PCM.
 
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KevinC

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Jan 11, 2022
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I'm not sure if you've found a solution, but just adding a thought - what you describe is exactly the experience I've had when I've had motorcycles with clogged carb jets. It'll start and rev in neutral without a problem. Sometimes you can get it to crawl along in first but .... it "moves, bucks, and runs like dookie." And as soon as you up the throttle or try to switch to second it cuts out.

Of course there's a lot different between a motorcycle with a carb and our cars - but you might look at the O2 and fuel sensors, or maybe something else in the fuel injection or delivery system - and if it's been sitting as it sounds like it has, I wonder if it's not electrical and might be a result of broken down / gunky gas getting into the system.
 
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nickyb

WAIT,you now have a pair?
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Apr 3, 2009
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One thing you said stuck out, bad motor mount.I
This is easy to check, have someone let the clutch out in gear while you observe . If the motor lifts up maybe just maybe it's pulling on some wires.
In reverse it would 'nt pull the same direction so check it out.
 
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CAMTWO1070

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Dec 17, 2021
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What Im leaning towards is the reverse switch.....Sounds crazy but with my moates chip I can see what gear Im in on the moates dashboard and I have a TKO600 5 speed..............
 
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manicmechanic007

5 Year Member
Sep 26, 2017
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I sure would be inspecting the main loom real closely as you are hitting the clutch
Chaffing of the main loom near the mass jacket or pedal support has been an issue
As far as what you have done, you had better recheck all of that too and inspect those harnesses real close
Chances are your pedal support is moving and chaffing wires or even the engine moving and chaffing the main engine loom as it moves
 
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manicmechanic007

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Sep 26, 2017
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Redbeard,
Wiggle test the harness is what they used to have us do
And with the star tester hooked up (it would beep if a signal or power wire was interrupted)
Used to see the engine harness / injector harness chaff at the back of the upper intake on trucks
When you put them in drive they would run like crap. Wiggle testing the harness found the culprit
Pulled the upper intake and saw the frayed wires. Repaired that
Crown Vics used to do the same. Never seen it on a Mustang but you should check that too
 
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Mar 26, 2022
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I was able to drive my car today, I still don't know whats going on with it though. I couldn't get it over 3,000 RPM's or give it too much throttle at once or it would cut out and the cluster needles would bounce up and down, and it said no to big hills (had to go up those in reverse with all the throttle I wanted) but all in all I drove it a good 10 miles. Still can't wrap my mind around what it could be. Thoughts? I'm wondering if its the alternator cutting out when its under load(that would explain the cluster), TPS, or a bad fuel filter.
 

manicmechanic007

5 Year Member
Sep 26, 2017
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One thing you said stuck out, bad motor mount.I
This is easy to check, have someone let the clutch out in gear while you observe . If the motor lifts up maybe just maybe it's pulling on some wires.
In reverse it would 'nt pull the same direction so check it out.
Damn straight 3.0 and 3.8 Taurus used to unplug O2 sensors with bad motor mounts