HP Tuner Interface
Thread Starter
Staging Lane
Joined: Mar 2008
Posts: 55
Likes: 4
HP Tuner Interface New motor installed, 99 Z28, motor runs rough, turn motor off, hook up interface and laptop, cranked up the engine and it runs good, unplugged the interface while motor is running and it starts to run rough, plug it back in and it runs good. what is up with that, any ideas?
Thread Starter
Staging Lane
Joined: Mar 2008
Posts: 55
Likes: 4
Thx minytrker, there are only 3 grounds on the back of the LH head, none that I know of on the RH head. the 3 on the LH are connected hard at the head but I haven't chased down those grounds at their other ends.
the 2 grounds on the DTC rang out solid and the orange power wire has 12 volts. don't understand why it runs good with the interface hooked up and bad when its disconnected.
the 2 grounds on the DTC rang out solid and the orange power wire has 12 volts. don't understand why it runs good with the interface hooked up and bad when its disconnected.
TECH Fanatic
Joined: Dec 2017
Posts: 1,467
Likes: 265
From: Bossier City, Louisiana
Could it be that the two grounds in the OBD2 connector are assisting / supporting a bad ground situation at the engine?? Pin 4 and Pin 11 may be helping here while the interface is in use.
Rick
Rick
Thx minytrker, there are only 3 grounds on the back of the LH head, none that I know of on the RH head. the 3 on the LH are connected hard at the head but I haven't chased down those grounds at their other ends.
the 2 grounds on the DTC rang out solid and the orange power wire has 12 volts. don't understand why it runs good with the interface hooked up and bad when its disconnected.
the 2 grounds on the DTC rang out solid and the orange power wire has 12 volts. don't understand why it runs good with the interface hooked up and bad when its disconnected.
Every time I have seen this it was a bad or broke ground on back of the head. When you plug in to the odb2 its grounding through there. Check and make sure a wire didn't break off the eyelet on one of the grounds.
Thread Starter
Staging Lane
Joined: Mar 2008
Posts: 55
Likes: 4
I be damned, I pulled the intake off and guess what I found. One of the 3 ground wires to the LH head was buster, ring terminal was busted. I had the trans off and looked up at those 3 grounds and they looked good to me, guess my eyes were lying to me. Will let you know how it runs thanks guys.
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The first time this happened to me 15+ years it took awhile to figure out. Customer drove here, changed injectors, I plugged in and tuned it. When they got ready to leave I took out my laptop and the car wouldn't start. Plug laptop back in and it would fire right up. Same thing happened to them, one wire broke off eyelet when they took off the fuel rails.
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Originally Posted by rayrat
I be damned, I pulled the intake off and guess what I found. One of the 3 ground wires to the LH head was buster, ring terminal was busted. I had the trans off and looked up at those 3 grounds and they looked good to me, guess my eyes were lying to me. Will let you know how it runs thanks guys.
Darth, don’t you know the ground currents are way different on the front of the engine?
Just kidding! 😊
Great catch on the ground minytrker. That lug, that bolt, and those wires have tripped up many folks.
Had an LS swapped Solstice in the shop that had random complete weirdness going on and it turned out the customer forgot to tighten that bolt.
Ron
Just kidding! 😊
Great catch on the ground minytrker. That lug, that bolt, and those wires have tripped up many folks.
Had an LS swapped Solstice in the shop that had random complete weirdness going on and it turned out the customer forgot to tighten that bolt.
Ron
Does anyone know where exactly the other ends of those ground wires go? I originally had 3 (I think) with ring terminals attached to the back of the heads. After everything was apart, and then put back, I could only find two. I even have a picture which shows a 3rd one (I think), but it's just disappeared. I haven't had any electrical problems though, in fact I did have a problem before everything was apart, where I'd turn the key to start and nothing would happen, then after some tries it would work - now since everything was put back together that hasn't happened even once, which is weird.
Originally Posted by RonSSNova
Darth, don’t you know the ground currents are way different on the front of the engine?
Just kidding! 😊
Great catch on the ground minytrker. That lug, that bolt, and those wires have tripped up many folks.
Had an LS swapped Solstice in the shop that had random complete weirdness going on and it turned out the customer forgot to tighten that bolt.
Ron
Just kidding! 😊
Great catch on the ground minytrker. That lug, that bolt, and those wires have tripped up many folks.
Had an LS swapped Solstice in the shop that had random complete weirdness going on and it turned out the customer forgot to tighten that bolt.
Ron
