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

Datalog of problem I'm having

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Old May 17, 2006 | 07:11 PM
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Default Datalog of problem I'm having

http://members.shaw.ca/fbody_god/Gripdiag1.csv

The car surges and tries to die at idle. Note the spark advance.
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Old May 17, 2006 | 09:04 PM
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Can a bad opti cause this?
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Old May 17, 2006 | 09:13 PM
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Some things I notice real quick.
Knock counts going nuts at idle, this is a problem. Looks like it might be a simple exhaust leak but that is a problem to fix.
You IAC is maxed out, what TB are you using?
Add some timing at idle after figuring out why you are pulling timing at idle.

This is a 93 and you have to burn chips?
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Old May 17, 2006 | 11:03 PM
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If he is getting knock at idle why add timing? Mabey it's pulling timing because of knock retard? Id clean the passages for the iac and clean the t/b.
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Old May 18, 2006 | 12:32 AM
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I'm running true duals with an LE2 heads and cam package. Its loud and probably causing some false knock.

When I disconnected the knock sensor it still idled like crap.

Running the stock TB ported to 52mm.

Yes I have to burn chips for the 93.
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Old May 18, 2006 | 03:18 AM
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You cant guess off hand if it's false knock. Get some racing fuel and see if it goes away. Thatll tell ya. Disconnecting the knock sensor is the wrong thing to do.
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Old May 18, 2006 | 06:26 AM
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Noticed I said add timing once he figured out the knock issue.
I have not seen too many cars with that low of a timing set at idle, i typically see in the 25-30* range at idle. NICE and Crisp!!
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Old May 18, 2006 | 06:48 AM
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I switched from 91 octane to 94 octane which is the highest I could find. No difference.

Could a bad opti cause retard? Bad ICM?
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Old May 18, 2006 | 07:26 AM
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Originally Posted by Gripenfelter
I switched from 91 octane to 94 octane which is the highest I could find. No difference.

Could a bad opti cause retard? Bad ICM?
When you switched, was the tank empty? it takes alot of higher octane gas to raise the octane of any gas when mixing it.

I do not think a bad opti would cause retard, would it cause bad driveability yes but not retard.
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Old May 18, 2006 | 07:29 AM
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Have you tried to open the blades any more? The IAC is maxed out and you said it was almost dieing at idle, that tells me it is not getting enough air at idle.
If you keep your foot on the pedal to give it a little more gas/air does it idle?
If so, then you can either open up the TB or try more idle RPM, but I would think 900 would be plenty if it is getting the air needed.

And is this condition while driving and coming to a stop or just sitting there idleing? IF coming to a stop, do you have the speedo working?
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Old May 18, 2006 | 07:59 AM
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Speedo works fine.

I completely drained the tank of the rest of the 91 octane by jumping the pump with 12 volts and disconnecting the fuel line at the fuel filter.

It has 100% 94 octane and it didn't change anything.

It idles low even in open loop (after resetting the PCM) and doesn't start to really surge till closed loop.

I'll play with the TB stop screws a bit and see what happens.

I revved it up last night and slowly revving it, it sounds fine. When you go WOT, it misses...makes popping noises. So I won't be doing that again.
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