Engine Dies when Shifted into Gear
05-28-2011, 06:15 PM
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Engine Dies when Shifted into Gear So I just finished my swap of a LQ4 and 4L80E into a 1986 Suburban. It fires right up and idles perfect however as soon as I attempt to shift into any gear besides park or neutral it dies. I dont know if this is a wiring issue or a tuning issue because the only changes I made in the tuning department was shutting VATS off to start the engine. Any help is greatly appreciated.
05-28-2011, 09:41 PM
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Not sure about IAC, the guy with HP tuners is gone for the next couple days. As for the converter or trans, I don't think there is anything wrong with either, it came out of a running/driving wrecked vehicle so I am assuming they both work. May be a stupid question but how does the IAC control the shifting? I'm thinking its something in the wiring or tuning. Do you happen to know what wires need tested on the trans plug to make sure its getting the power it needs for the solenoids?
05-29-2011, 08:00 AM
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idle air control valve, when the car is shifted into drive or from drive to park the engine has a load put on it or taken off. that would drop the engine rpm or raise it.
the IAC would control that portion.
the trans or converter....i dont remember this theres a torque converter clutch? i think thats what its called....maybe someone can help me out, but when shifted into drive, it has to release or lock for the car to idle in drive.....
the IAC would control that portion.
the trans or converter....i dont remember this theres a torque converter clutch? i think thats what its called....maybe someone can help me out, but when shifted into drive, it has to release or lock for the car to idle in drive.....
05-29-2011, 09:14 AM
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It sounds like it's an issue more with the engine, than the transmission.
The torque converter clutch should only lock up when cruising on the highway.
You could try raising the RPM's slightly (with your other foot on the brake too!) when you shift into gear. If the RPM's go down when you shift into gear, but you are able to keep the engine running with throttle....I would bet it's an issue with the IAC.
Maybe you could try disconnecting the driveshaft (as to not put so much of a load on the engine) and see if still does it.
The torque converter clutch should only lock up when cruising on the highway.
You could try raising the RPM's slightly (with your other foot on the brake too!) when you shift into gear. If the RPM's go down when you shift into gear, but you are able to keep the engine running with throttle....I would bet it's an issue with the IAC.
Maybe you could try disconnecting the driveshaft (as to not put so much of a load on the engine) and see if still does it.
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05-29-2011, 04:13 PM
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It sounds like it's an issue more with the engine, than the transmission.
The torque converter clutch should only lock up when cruising on the highway.
You could try raising the RPM's slightly (with your other foot on the brake too!) when you shift into gear. If the RPM's go down when you shift into gear, but you are able to keep the engine running with throttle....I would bet it's an issue with the IAC.
Maybe you could try disconnecting the driveshaft (as to not put so much of a load on the engine) and see if still does it.
The torque converter clutch should only lock up when cruising on the highway.
You could try raising the RPM's slightly (with your other foot on the brake too!) when you shift into gear. If the RPM's go down when you shift into gear, but you are able to keep the engine running with throttle....I would bet it's an issue with the IAC.
Maybe you could try disconnecting the driveshaft (as to not put so much of a load on the engine) and see if still does it.
05-29-2011, 04:21 PM
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This is my first swap and and I'm not sure what the norm is when you get the engine fired up and running if you can just hop in and go or not but I was told right now that I need to let the engine run for at least a half hour straight to let the computer "learn". Anyone know if this is true? It is a stock motor with the stock computer and everything else is stock so I'm not sure what the computer has to learn.
05-31-2011, 10:53 AM
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Does it kinda bang or lunge when you put it in gear? That would indicate a stuck converter. You need to check for codes. And with the tuner hooked up try shifting into gear and see if you are losing comm. That would indicate a wiring issue. What kind of harness are you using.
05-31-2011, 01:59 PM
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Does it kinda bang or lunge when you put it in gear? That would indicate a stuck converter. You need to check for codes. And with the tuner hooked up try shifting into gear and see if you are losing comm. That would indicate a wiring issue. What kind of harness are you using.
I am using the stock harness and factory fuse box. It doesn't bang into gear or anything. It doesn't try to spit and sputter and run, It is as if the key were just turned off and all power to the motor has been shut off. As for being a bad converter, I dont think it is because it came out of a running driving wrecked truck. The engine and trans were together when I got it in a crate so its never been apart as far as I know so it shouldn't be the coverter but anything is possible. I am pretty sure its a wiring issue and the guy with hptuners will be back tomorrow so I will be able to see if it is throwing any codes.
05-31-2011, 02:03 PM
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05-31-2011, 09:57 PM
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Disconnect the trans connector and the park/neutral safety switch after you start it up. Then put it in gear and see what happens. If the problem is something transmission electrical, it should go away and the vehicle stay running in gear since the PCM wouldn't know you changed gears. If it still just dies, probably the torque converter clutch stuck on.
06-11-2011, 03:55 PM
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Disconnect the trans connector and the park/neutral safety switch after you start it up. Then put it in gear and see what happens. If the problem is something transmission electrical, it should go away and the vehicle stay running in gear since the PCM wouldn't know you changed gears. If it still just dies, probably the torque converter clutch stuck on.