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Thread: LSA wont idle, need advice before tearing into engine any further.

  1. #1
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    Sep 2014
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    LSA wont idle, need advice before tearing into engine any further.

    We recently completed a LSA swap in a 79 caprice. After a lot of tuning and bug sorting the thing runs great but idle is all over the place and it just wont stay running without feathering the throttle. Some background on this engine... Our customer bought it as a take out from a well known LSA/Cadillac tuner and we are told it is a CTS-V engine but it has a ZL-1 supercharger cover on it. We are finding out it appears they cobbled it together with stuff they had laying around... They apparently did a cam swap on this as well. We have had issues from day one. After startup we determined that it had a bad miss. We found that during the cam swap they forgot #7 exhaust pushrod- whoops. Long story short, it bent the intake pushrod. We fixed that snafu but we never tore into the engine, we scoped it and it appears we lucked out by just replacing all the push rods and making sure they are all installed, DUH. Compression (160 cold) and leak down (1-3%) are solid across the board. We have even verified the cam isnt off a tooth. We have a very experienced tuner who is tuning the car and he has tuned many cars for us in the past and he is stumped as well. We are all extremely capable of diagnosing and working on these types of problems but this one has us scratching our heads. We are leaning towards a vacuum leak but before taking the blower off and digging further I want to make sure we aren't missing something that maybe one of yall gurus have come across before. I dont know what he has done tuning wise but what I do know is he stated that he ended up making a completely custom map because everything has been off and all the "normal" typical tunes aren't jiving with our set-up for some reason. Even with the custom map it wont idle worth a shit. Any help or insight would be greatly appreciated.

    Speartech LSA harness with E67 PCM (pt#12636660)TIS flashed as 07 TBSS and TCM (PT#24252114)
    07 TBSS pedal
    TBSS throttle body
    PT#12591290 S/C Snout MAP Sensor
    PT#12592525 S/C case MAP sensor

  2. #2
    Senior Tuner SultanHassanMasTuning's Avatar
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