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

Lt1 trans am idle issue?

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Old 04-05-2016, 01:39 PM
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Default Lt1 trans am idle issue?

I have a 1995 trans am. At idle it shakes pretty bad when cold gets better as it warms up but never goes away completely. Going down the road it feels great. Other details about the car it has ltcc coil on plug system recently installed, AIR system was just recently deleted, and has been tuned with tuner cats to delete all AIR codes and functions and also set fans to come on at 215 and 220. Every thing else is stock. I did check vacuum on intake seems to be around 18 Ish and no vacuum leaKS any where I can find.
Old 04-05-2016, 02:08 PM
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Do you have a way to watch your IAC counts?
Old 04-05-2016, 05:09 PM
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Originally Posted by Jaxem
Do you have a way to watch your IAC counts?
I have the 9495 scan software for it I'll watch it and see what it is doing. Have not used it yet so we will see but I did use the cats programmer to turn it to air speed density mode to see if that did anything also had no effect so I turned it back. Will post tonight with IAC info
Old 04-05-2016, 07:02 PM
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Originally Posted by Jaxem
Do you have a way to watch your IAC counts?
Here is the info it will give me on cold start
Old 04-06-2016, 01:09 AM
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Can you post a longer log? One that shows it go into closed loop? You can attach it as a zip file.
Old 04-06-2016, 07:02 AM
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Yes I will get it tonight and thanks for the continued help
Old 04-09-2016, 08:16 PM
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i attached a long log of it running and the exe needed to watch the log. I did try turning off the fans and letting it get to the 220s and it did smooth out alot. bad gas maybe?DLOG-Save-2016Apr09-194005-2G2FV22P2S2247222.zip

Scan9495.zip
Old 04-10-2016, 05:18 PM
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According to your log you are running pig rich. It's maxing out the LTBLM limits to the minimum side of things (pulling as much fuel as it's allowed to), on top of that the STBLMs are well below 100, like 60-80 range (128 is the target, but STBLMs rarely sit right at 128, they constantly fluctuate around 1280 +/- 10 ish, maybe a bit more, but never constantly more than 15 off once the LTBLM stabilizes), that means it trying to pull a lot more than what the PCM limits long term (LTBLMs).

Did you change anything else with the LTCC conversion? If not, maybe the timing is way off?? The LTCC still uses the Optical Position Sensor, so it must still be installed correctly for everything to work right. If it's clocked off, it will have timing issues and run poorly, if it runs.

It could be a false rich condition, bad O2s maybe? Does it smell rich? Burning your eyes? If you have a cat, it'll mask a lot of it. But, if you are rich, you'll clog up the cat and foul out the plugs causing even more issues later.
Old 04-10-2016, 06:09 PM
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Well ran it out of gas put new in still has not fixes the idle. It fine at 200+ degrees but really rough till then
Old 04-10-2016, 06:15 PM
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The only things I changed was adding the ltcc and deleting the air system (pump, hoses, lines fuse, and relay) the fans kicking on at 215 but that was tuned in over a rear ago and still running the same opti from before (never removed it). It does seem to have some oil on the distributor but did before the change also) so not sure if it went bad or not.
Old 04-10-2016, 06:17 PM
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It does smell very rich but has no cats
Old 04-10-2016, 06:52 PM
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Have you checked spark strength with a spark strength tester? If you still have all the original Opti stuff, you could reinstall the wires, coil, and ICM (bypassing the LTCC) and see if that cures it. If so you know it's something with the LTCC. If not, it's something else.
Old 04-10-2016, 08:31 PM
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I checked fuel pressure and it dials up to 40ish and drops fast
Old 04-10-2016, 10:35 PM
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Originally Posted by Jesse Cotten
The only things I changed was adding the ltcc and deleting the air system (pump, hoses, lines fuse, and relay) the fans kicking on at 215 but that was tuned in over a rear ago and still running the same opti from before (never removed it). It does seem to have some oil on the distributor but did before the change also) so not sure if it went bad or not.
There could be somewhere in all the AIR stuff where you've introduced a vacuum leak, which will set you rich, i'm fighting a similar issue at the moment, not quite as bad as yours, but i still haven't found my cause



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