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67 Camaro Chokes and Stalls

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Old 06-26-2018, 12:18 PM
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Default 67 Camaro Chokes and Stalls

1967 Camaro with 96 [Camaro] LT1 swap (with TH700r)

Just recently purchased; swap was already done.

On cold start, the car fires up and runs fine – well not that fine, but I’ll get to that. After warming up to operating temp, it drives for some time, but then will stall and won’t start until it cools back down – 20-45 minutes later. Any idea what’s going on? That’s the first issue.

The other issue is that while running, if the accelerator is pressed “too hard,” it chokes and sputters as if gas is being cut off. It eventually evens out, but there is no "getting on it." Since purchase, everything from fuel tank up to engine has been replaced – tank, pump, and lines. At wits end on what could be causing it. Any suggestions?

Thanks
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Old 06-26-2018, 12:52 PM
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Fuel pump and/or fuel injectors are my guess. Perhaps the fuel pump is overheating and injectors are shot?
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Old 06-26-2018, 01:04 PM
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Any idea if there is any tune in the PCM? Do you have a way to look at the engine data to see what's going on, with fuel and timing? Have you checked base engine, oil pressure, compression, leak down, vacuum leaks,etc?
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Old 06-26-2018, 01:34 PM
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Originally Posted by t2true View Post
1967 Camaro with 96 [Camaro] LT1 swap (with TH700r)


On cold start, the car fires up and runs fine – well not that fine, but I’ll get to that. After warming up to operating temp, it drives for some time, but then will stall and won’t start until it cools back down – 20-45 minutes later. Any idea what’s going on? That’s the first issue.Thanks
That is classic ICM fail symptom

if you replace, use heat sink paste behind it. Typically $1 at auto part stores

as mentioned check fuel pressure first to rule FP issue in/out....especially when stumble occurs
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Old 06-26-2018, 03:37 PM
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Originally Posted by SS RRR View Post
Fuel pump and/or fuel injectors are my guess. Perhaps the fuel pump is overheating and injectors are shot?
Thanks for the input. I've thought of fuel injectors and plan to investigate.
The in-tank fuel pump, however, is new.
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Old 06-26-2018, 03:43 PM
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Originally Posted by biketopia View Post
Any idea if there is any tune in the PCM? Do you have a way to look at the engine data to see what's going on, with fuel and timing? Have you checked base engine, oil pressure, compression, leak down, vacuum leaks,etc?
Thanks for the feedback. I have little information on the swap, other than print-outs from LT1swap.com (which are just wiring schematics that I'm familiar with). I do not know if a tune was done, although, it was a consideration. (I also do not know if the PCM was flashed or not. I would assume it was, at least to remove VATS.) I've tried to hook up a reader to the OBDII port, however, it has no power, like it was not connected properly. That's a to-do item.
Another problem is that none of the stock gauges work - speedo/fuel. An external temp gauge was installed that works, and it reads normal.
Oil pressure and compression have not been checked. Vacuum has. I am not familiar with "leak down."
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Old 06-26-2018, 03:44 PM
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Originally Posted by ****** View Post
That is classic ICM fail symptom

if you replace, use heat sink paste behind it. Typically $1 at auto part stores

as mentioned check fuel pressure first to rule FP issue in/out....especially when stumble occurs
What is ICM?
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Old 06-26-2018, 04:18 PM
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Originally Posted by t2true View Post
What is ICM?
Ignition control module

Here's a few threads that start out just like yours. Sounds like ***** hit the nail on the head with that one.
http://www.ls1lt1.com/forum/lt1-%7C-...9-bad-icm.html
https://ls1tech.com/forums/lt1-lt4-m...ol-module.html
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Old 06-26-2018, 04:58 PM
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Originally Posted by t2true View Post
What is ICM?
Ignition Control Module. Its above the coil on DS head....assuming that has not been relocated with the LT1 transplant in the 67
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Old 06-27-2018, 08:45 AM
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That's good information about the ICM. I am most familiar with the LS-based engines which does not have a separate ICM.
The ICM will surely be investigated to root out the problem.

I still need to figure out the "choking" symptom when the gas is pressed hard. I may need to get a fuel pressure gauge and also check the fuel injectors.
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Old 06-27-2018, 09:01 AM
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It's possibly a combination of ICM and Opti acting up. I bet both symptoms are a result of each other. Pull the cap and make sure the sensor is in good shape and that the rotor is tight, then test or replace with a know good one the ICM and see if that fixes your issues.
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Old 06-27-2018, 10:46 AM
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Originally Posted by t2true View Post
That's good information about the ICM. I am most familiar with the LS-based engines which does not have a separate ICM.
The ICM will surely be investigated to root out the problem.

I still need to figure out the "choking" symptom when the gas is pressed hard. I may need to get a fuel pressure gauge and also check the fuel injectors.
typically ICM fail is either the car won't start at all or after it warms up it shuts off and won't re-start until it cools down.....but what I recently experienced is car did start but you had to spoon feed the gas to keep it running as if the car was running out of gas or fuel pressure was low.....it was the ICM

I would first check fuel pressure just to rule in/out a fuel problem.

If FP is good I would replace the ICM. AC Delco only. rockauto.com

if still a problem...Opti
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Old 06-28-2018, 07:16 AM
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Thanks again guys. Your information is most helpful. Some time will be spent this weekend working on these issues.
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Old 08-17-2018, 03:42 PM
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Well, problem not solved. The ICM has been replaced; all injectors pulled and cleaned; but hot-start-fail is still occurring.
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Old 08-17-2018, 04:03 PM
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have you check fuel pressure?

what brand ICM did you buy
what brand opti?

did you test coil?

fyi, faulty ICM can corrupt a coil and vice versa...

about the floor it and sputter....is it a stock TB size (48mm) or larger and has the motor been tuned for whatever mods it does have
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Old 08-20-2018, 08:45 PM
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Originally Posted by ****** View Post
have you check fuel pressure?

what brand ICM did you buy
what brand opti?

did you test coil?

fyi, faulty ICM can corrupt a coil and vice versa...

about the floor it and sputter....is it a stock TB size (48mm) or larger and has the motor been tuned for whatever mods it does have
ICM is ACDelco.
Haven't swapped Opti.

Unfortunately, the OBD is not working. I don't know if it's because it's not connected or what; still need to figure that out. So, I can see any codes that it may be showing.
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Old 08-21-2018, 06:09 AM
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Originally Posted by t2true View Post
ICM is ACDelco.
Haven't swapped Opti.

Unfortunately, the OBD is not working. I don't know if it's because it's not connected or what; still need to figure that out. So, I can see any codes that it may be showing.
I'd start there, being able to read the data and view codes will give you some good direction on where to look and what to test.
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Old 08-21-2018, 10:46 AM
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Originally Posted by t2true View Post
I may need to get a fuel pressure gauge...
Good idea.
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Old 08-22-2018, 06:51 AM
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Make sure that the coolant sensor is plugged in, so the computer knows the correct temp. There is a sensor in the cylinder head for the gauge in the dash, and there is a sensor in the front of the water pump for the pcm. If that sensor isn't plugged in, the pcm will leave your car in cold-start mode, and it will be pig rich. It will die after a few minutes, and be very difficult to start.
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Old 08-22-2018, 12:08 PM
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Originally Posted by joelster View Post
Make sure that the coolant sensor is plugged in, so the computer knows the correct temp. There is a sensor in the cylinder head for the gauge in the dash, and there is a sensor in the front of the water pump for the pcm. If that sensor isn't plugged in, the pcm will leave your car in cold-start mode, and it will be pig rich. It will die after a few minutes, and be very difficult to start.
Interesting. I will check that out. Thanks
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