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Old 04-04-2012, 12:19 AM   #1
VettezukiVettezuki is offline
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Default The Tale of the Stumbling Vette

Well I've had this issue of the Vette not gettming more than half a mile or so before it would go into horrific lurches/stumbling. It's a Paul's (ls1z28's) house now and he's trying to figure out WTF is wrong. And it's a mystery so far.

Every electrical connection and relay has been checked. The harness has been inspected for any frayed wires. The alternator has been checked, the battery. the computer has been checked, including disassembly to check for cracked soldering. Nothing is wrong. We're down to two ideas, and if that doesn't solve it the one remaining is a real bitch assuming we haven't forgotten anything else.

So tomorrow, he'll be replacing the cam position sensor. It isn't throwing ANY codes, but it is possible to fail intermittently without throwing a code apparently. After that, we'll reflash the computer. The negative battery cable wasn't really well connected and showed signs of arching, *maybe* it corrupted some part of the flash with a surge; but that's a fairly wild hypothesis. So what are we left with then? Crank shaft end play, which can cause this kind of behavior. But that means removing the engine, etc. Not something I have money for now. So hopefully it's the cam position sensor.

The only thing we can say now is that it doesn't appear to be anything in the electrical system itself and seems to only happen when the computer goes into closed loop. If you fire it up and drive it immediately, it's ok for a minute or two.

On the upside, we discovered the MAF was dying, replaced that and now all the misses are gone. He's replaced the ignition switch, which was fried and was probably related to the poor starting situation. We're replacing the negative cable (already replaced the positive) just to make sure there's good current, useful thing to do anyway.
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Old 04-04-2012, 12:42 AM   #2
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I really doubt it's a camshaft issue, have you checked all things related to the fuel system?
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Old 04-04-2012, 01:08 AM   #3
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I really doubt it's a camshaft issue, have you checked all things related to the fuel system?
Pump and relays, yes. The filter regulator may be a little clogged, but that wouldn't explain this behavior.
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Old 04-04-2012, 07:26 AM   #4
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Does he have a scan tool that can do data logging? We need to see what data is changing/dropping out. How close is is the current location to Fullerton. I can bring a good scan tool Sat evening .
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Old 04-04-2012, 10:55 AM   #5
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Does he have a scan tool that can do data logging? We need to see what data is changing/dropping out. How close is is the current location to Fullerton. I can bring a good scan tool Sat evening .
He has the Tech II. Will that do it?
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Old 04-04-2012, 10:59 AM   #6
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Yes
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Old 04-04-2012, 11:00 AM   #7
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He has the Tech II. Will that do it?
Yes ! Probably better than mine. Tech II is the GM factory tool.
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Old 04-04-2012, 11:44 AM   #8
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He has the Tech II. Will that do it?
A Tech II is the best tool for the job...

What is the fuel pressure?
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Old 04-04-2012, 12:47 PM   #9
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A Tech II is the best tool for the job...

What is the fuel pressure?
Around 58 and stable.
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Old 04-04-2012, 04:40 PM   #10
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Just got a text. Still driving him nuts. This is some crazy ass gremlin.
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