LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Car shuts off when braking and stopping

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Old 10-20-2006, 07:10 PM
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Default Car shuts off when braking and stopping

Every time I come to a stop the car shuts off. Just driving for 3 minutes Ill hold the brakes to stop and the idle rpm's drop really low and shuts off. What could be causing this?
Old 10-20-2006, 07:53 PM
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Check for vacuum leaks.
The brakes eat up a lot of vacuum.
Old 10-20-2006, 08:49 PM
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Yea, Vacuum is probably the one there..
Wierd that it's doin that..
Old 10-21-2006, 01:20 AM
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If I press the brakes at idle everything is ok. It's when I'm coming to a stop the idle drops and dies.
Old 10-21-2006, 03:49 AM
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How does the car run at idle? Don't suppose you have datalogging software?

Few thoughts:

If you don't have datalogging software, you could use a vacuum gauge to see what the engine is pulling. Otherwise, if you have datalogging capabilities, subtract the MAP readings from the BAR readings to get a general idea of engine vacuum (I prefer using "Hg as opposed to kPa).

Just a thought, but I'd be curious to see the idle-air controller (IAC) numbers -- both while parked at idle and while decelerating. With your modifications, it's possible that you simply don't have enough volume of air entering the engine (with the throttle closed) to sustain the engine. That is, the IAC would be maxed out at 160 counts and still wouldn't be allowing enough air in. The solution would either be to either crack open the throttle blades via the throttle stop screw (which may have adverse effects), or try to enlarge the IAC passage in the BBK TB.

Additionally, how many miles are on this engine (as I see it's a rebuild)? I take it the rings have had time to seat -- has the compression ever been tested?

Lastly, depending on what you find out about the engine, you might need to look into running a vacuum reserve tank for the brakes. It looks like you have a decent sized cam, though the extra cubic inches will effectively "tame" the camshaft...
Old 10-21-2006, 04:56 AM
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Originally Posted by Alex94TAGT
How does the car run at idle? Don't suppose you have datalogging software?

Few thoughts:

If you don't have datalogging software, you could use a vacuum gauge to see what the engine is pulling. Otherwise, if you have datalogging capabilities, subtract the MAP readings from the BAR readings to get a general idea of engine vacuum (I prefer using "Hg as opposed to kPa).

Just a thought, but I'd be curious to see the idle-air controller (IAC) numbers -- both while parked at idle and while decelerating. With your modifications, it's possible that you simply don't have enough volume of air entering the engine (with the throttle closed) to sustain the engine. That is, the IAC would be maxed out at 160 counts and still wouldn't be allowing enough air in. The solution would either be to either crack open the throttle blades via the throttle stop screw (which may have adverse effects), or try to enlarge the IAC passage in the BBK TB.

Additionally, how many miles are on this engine (as I see it's a rebuild)? I take it the rings have had time to seat -- has the compression ever been tested?

Lastly, depending on what you find out about the engine, you might need to look into running a vacuum reserve tank for the brakes. It looks like you have a decent sized cam, though the extra cubic inches will effectively "tame" the camshaft...
At idle the car surges from 900 to 1300 rpm's. I have datalogging software but I cant get it to work with my 93. It's like Datamaster doesnt see my car and freescan doesnt work with 93's.
Ive tried adjusting the throttle blades but doing it that way it idle really high and surges higher.
The engine has been broken in. Had the engine in my Camaro for break in before moving it to the 93 corvette. In the Camaro it drove very well. No idle issues or anything special. Once it got into the Vette it went crazy. I really wish I could get something to datalog it so I could see what was going on. I think their may be a vaccum leak but looking over it I dont see it. Where is the best place to measue vacuum with a gauge? My next step is the IAC. I want to remove the throttle body also and enlarge the hole. What else should I be looking at?
Old 10-21-2006, 06:51 AM
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What version of Datamaster are you using?

If I'm understanding your situation correctly, I wasn't sure if perhaps your Camaro was a 1994-1997 and that's when you originally got Datamaster EE. Naturally, the 1993's require Datamaster DA. If you already got that covered, then nevermind.

Maybe there's just a communication error. Are you using a USB or the DB9/rs232 serial-style ALDL cable? Have you double-checked your COM port settings? The above link to TTS also has that "ALDL-Test" program -- might give that a shot. It seems I remember testing my cable using Hyperterminal, though I don't recall the directions to do so...

At this point, I think Datamaster would be your best weapon to fight this problem. Lets try to get that working...
Old 10-21-2006, 07:17 AM
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Originally Posted by Alex94TAGT
What version of Datamaster are you using?

If I'm understanding your situation correctly, I wasn't sure if perhaps your Camaro was a 1994-1997 and that's when you originally got Datamaster EE. Naturally, the 1993's require Datamaster DA. If you already got that covered, then nevermind.

Maybe there's just a communication error. Are you using a USB or the DB9/rs232 serial-style ALDL cable? Have you double-checked your COM port settings? The above link to TTS also has that "ALDL-Test" program -- might give that a shot. It seems I remember testing my cable using Hyperterminal, though I don't recall the directions to do so...

At this point, I think Datamaster would be your best weapon to fight this problem. Lets try to get that working...
DM35xDA is what I have. Ive used Datamaster before with EE same laptop same usb cable and it worked fine. Ive also double checked the com ports. The only thing out of place there is I cant seem to use com ports 1-3. Only 4 is availible. That may be why it isnt working. If I knew how to free up 1-3 ports I would use por 1, which is the one I use to use. Ill also try the test program. Never noticed that before.
Old 10-21-2006, 08:17 AM
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What should my iac count be at when idling?
Old 10-21-2006, 08:39 AM
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This is probably not it, but I seen several cars (all have been FWD so far, but is still possible) that the TCC won't release after being driven long enough to get it warmed. I would suggest you try pressing on the brake pedal to see if you can feel the TCC relasing when just driving along. When those cars did this it felt like you were trying to stop a stick shift car without pushing the clutch pedal down. The TCC solenoid in the tranny was sticking on those problem vehicles.

Good luck, Ed
Old 10-21-2006, 09:02 AM
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Originally Posted by Ed Wright
This is probably not it, but I seen several cars (all have been FWD so far, but is still possible) that the TCC won't release after being driven long enough to get it warmed. I would suggest you try pressing on the brake pedal to see if you can feel the TCC relasing when just driving along. When those cars did this it felt like you were trying to stop a stick shift car without pushing the clutch pedal down. The TCC solenoid in the tranny was sticking on those problem vehicles.

Good luck, Ed
I'll look into it. When the torque converter locks and unlocks it shows up on the Datamaster correct? I finally was able to drive the car for 9 minutes to get a datalog. Can someone look at it for me and tell me what they think?
Old 10-21-2006, 09:12 AM
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IAC count had to stay maxxed out to drive it. It surged and sputtered at part throttle, it jump in and out of closed and open loops, BPW mS reading was in the yellow, and I had DTC 15 cool temp low. Anyone here good at reading this? I'm about to throw it into VEMaster.
Old 10-21-2006, 12:38 PM
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Feel free to shoot me the log file: alex94tagt@gmail.com

What were your coolant temp readings throughout the log? Were they really low and/or jumpy? It sounds like the coolant sensor in the waterpump housing might need to be replaced -- though, I'd check the electrical connector/wiring harness first. This could theoretically cause the open loop/closed loop issue, but it's still a little premature to say...

Sounds like the IAC is an issue.
Old 10-21-2006, 12:57 PM
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Originally Posted by Alex94TAGT
Feel free to shoot me the log file: alex94tagt@gmail.com

What were your coolant temp readings throughout the log? Were they really low and/or jumpy? It sounds like the coolant sensor in the waterpump housing might need to be replaced -- though, I'd check the electrical connector/wiring harness first. This could theoretically cause the open loop/closed loop issue, but it's still a little premature to say...

Sounds like the IAC is an issue.
Sent. The highest the temps got was 187F. Here's a lik to the file also:

http://d.turboupload.com/de/1110032/upfk3iozie.html#
Old 02-05-2013, 09:40 PM
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Originally Posted by Honda Hunter
If I press the brakes at idle everything is ok. It's when I'm coming to a stop the idle drops and dies.
Hey bro my buddy has a issue pretty close to the issue you had. He wanted me to ask you if you wouldn't mind giving him a call or if he could call you to go over some things. Thanks. His number is 209-648-7263 his name is Paul.
Old 02-05-2013, 09:41 PM
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Originally Posted by MAXXLIMIT
Hey bro my buddy has a issue pretty close to the issue you had. He wanted me to ask you if you wouldn't mind giving him a call or if he could call you to go over some things. Thanks. His number is 209-648-7263 his name is Paul.
Dude...this thread is

SEVEN YEARS OLD!
Old 02-06-2013, 09:49 AM
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Try a PM it's faster and it keeps dead threads buried where they belong




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