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

24x conversion help

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Old Jan 10, 2013 | 11:19 AM
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Default 24x conversion help

Just completed all wiring and also did a cam swap...I can get the at to start but only with opening up the throttle to allow more air in does it start, but its a hard start cranking and cranking...When it runs it idles with a backfire and sometimes wants to turn off? Also while its running the check engine light is blinking..anyone?
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Old Jan 10, 2013 | 12:01 PM
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back to the basics, 1) any codes stored? 2) what tune are you running? are you starting from Mike's tune that he provides with instructions and did you follow all the tuning directions? 3) make sure you've got the injectors pinned right and the coils pinned right for the easy trouble shooting.

Let us know how that turns out.
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Old Jan 10, 2013 | 12:10 PM
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when i did my swap it took me a little while to start and that was due to the the 3 wires on the cam sensor two were backward it runs but it takes a while to start.

but like said above start from number 1

did you pin the harness right swap coil and injector around.
did you get a good tune?
any codes
cam sensor wires
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Old Jan 10, 2013 | 12:14 PM
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I cannot read any codes yet..I just have the ls1 PCM with no tune except the rear 02 sensors were deleted and vats..is there anything else special to just get it running?

So which wires did you put backwards? I triple check every input but never really got exactly where the cam and crank wires pin into. Just what I have seen on here of what people have posted
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Old Jan 10, 2013 | 12:40 PM
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did you look at my guide I posted with pics? it gives you exactly where it all goes. Getting the cam/crank is crucial for the PCM to know where you are. Also, take the time and read what Mike wrote up in the instructions, there's a ton of value there. All of this is really move "A" to "B" location so it's not hard, but you do have to know where it is suppose to go and you should feel 100% certain that you moved it correctly.
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Old Jan 10, 2013 | 12:47 PM
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Originally Posted by blk3rdgen91
I cannot read any codes yet..I just have the ls1 PCM with no tune except the rear 02 sensors were deleted and vats..is there anything else special to just get it running?

So which wires did you put backwards? I triple check every input but never really got exactly where the cam and crank wires pin into. Just what I have seen on here of what people have posted
it was the A,B connectors on the cam sensot it self. and i think you have to get it reprogrammed. because of the coil swap and injestors. the knock sensor is getting false data and then the eu is trying to fix it by giving timing and fuel to the wrong cylinder. im not a programmer but thats what i got out of it when i talk to tpis when they were tunning it.
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Old Jan 10, 2013 | 12:59 PM
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Merim123...I used that pin out tht your talking about the pics and I have re checked about 3 times already..I think it might be the tune. Is there a special tune?

Tt383lt1.. That's what I'm wondering if I need a tune..I thought that as long as you swap the coil/injectors 2&3 and 4&7 it would be fine? Do I need to change my knock sensor to a 96-97 lt1?

I wanted to tune on a Dyno that's why I never Messed with the pcm
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Old Jan 10, 2013 | 01:12 PM
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the easest way to find out all of these question would be talk to tpis there number is 952448 6021 they sell and tune this swap for efi connections
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Old Jan 10, 2013 | 01:32 PM
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Thanks called them but they couldn't tell me what the difference was between ls1 base tune and 24x base tune...I'm still in the dark...I mean the only thing left is the PCM
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Old Jan 10, 2013 | 01:42 PM
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really? jim there tuner could not tell you? and i was thinking it has to be the tune as long as you have the wire good. im pretty sure the injectors are diffrent from a lt1 and ls1 so thats putting the wrong amount of fuel in. than the knock sensor is screwing up to. and btw how many knock sensor do you have? i heard you have to run a 97 knock sensor on the pass side. but im running one on my pass and driver side so i have two like the ls motor would. but hopes this helps. i would call a couple shops and get price on a base tune.
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Old Jan 10, 2013 | 01:51 PM
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Yea I have just one knock sensor.. That's what in trying to find a local spot that does tuning here in ft lauderdale..I remember there was a place called mad tuner but can't seem to find them
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Old Jan 10, 2013 | 05:04 PM
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Get it tuned. An LT1 won't run right on a stock LS1 PCM tune, in the injector bank select has to be changed among other things.
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Old Jan 10, 2013 | 05:46 PM
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the "only" difference in the tune is because of the difference in the regulator. Most tuners miss this, but it won't cause the car not to run, you just have to put in the size of your injectors in lb's all the way across the same. So if you have 30lb injectors, the values in the tune should all be 30lbs.

Second, you do need the 96+ obd2 connector, but I think it will run without it.

did you disable vats? what are you using for tuning? Mike has a sample file you can download from his site.
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Old Jan 11, 2013 | 12:30 AM
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the "only" difference in the tune is because of the difference in the regulator
Thats not the only thing, Like I mentioned above the injector bank select needs to be changed, if not the 02's will go rich on bank 1 and lean on bank 2 if left alone. The LT1 uses a return system so YES the IFR needs to be constant, BUT so does the offsetvsvoltsvsvac. For the speed to read correct the tach output resolution needs to be at 3 on high and low.

blk3rdgen91 put a scanner on it and you'll see what I mean on the fuel trims.
If you had hp tuners Id send you a file.
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Old Jan 13, 2013 | 09:36 AM
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Yea I spoke with lashway motorsports to have this pcm tuned...apparently he was saying that ls1 timing is different than lt1 time therefore causing the engine probly to run like crap...but I don't have hp tuners but am having this guy come and tune...vats was disabled and rear o2 sensors...I still have to have my ob1 connector converted to ond2 which is not hard so I can see what's going on and get my tune done
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Old Jan 13, 2013 | 09:47 AM
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I would just send the pcm for a start up file tune to someone who is familiar with the 24x conversion.
I did the conversion with no issue at start up---fired right up! I bought the LS1 pcm from Ion (Madz28) and told him I was doing the 24xconversion. After I had the car running, I took it to Jim@Speed Inc for dyno tuning.

Last edited by BOLO; Jan 13, 2013 at 01:17 PM.
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Old Jan 18, 2013 | 05:48 PM
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So went ahead and got a base tune spent 50 bucks...now it starts up right away. The only thing is now I still have a backfire at idle, so I re adjusted the roller rockers and double check all of them. Backfire improved but was still there. Could this still be because of the tune? I check for any vaccum leaks also didn't find any.
Has anyone had this problem?
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Old Jan 18, 2013 | 07:45 PM
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It still needs a good tune im sure, but as long as it is running, your in much better shape and a lot closer
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Old Jan 20, 2013 | 03:48 PM
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The code that comes up is P0106 I believe in backfiring because I'm running rich since my tune shut off the o2 sensors.
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Old Jan 22, 2013 | 05:46 PM
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Well I got a wideband and was running very lean so had the PCM add more fuel and boom runs good no backfire...so now it's just getting it on a Dyno and tuning hardcore
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