98 LS1 performance problem after header install
05-03-2009, 08:01 PM
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98 LS1 performance problem after header install I was tuning a guys car today. He installed LT's and a new exhaust system. Well i'm pretty positive some of the problem the car is having is due to the Y-pipe smacking the bottom of the car. The car is an A4, with headers, slp maf, ported tb other then that it's stock. After i done all the basic tuning stuff timing, tq management ect. ect. we took it for a spin to scan it. It feels good then it starts to bog really bad and it shifts at 5100rpm obviously that isn't correct. Nothing out of the ordinary on the scan except alot of knock i'm guessing alot from the Y-pipe banging cause i hardly touched the timing table.
Is there anything else that might be the problem? I've never ran into that before on anything i've owned or worked on, it seemed like it just hit a wall at 5100rpm hesitated and then it shifted. He said it didn't start doing this till the header install, that's why i said false knock but the more i think about it i wasn't sure if the PCM would make the car shift early if it had that much false knock or not. I'm kind of wondering if it could be the slp maf also.
Is there anything else that might be the problem? I've never ran into that before on anything i've owned or worked on, it seemed like it just hit a wall at 5100rpm hesitated and then it shifted. He said it didn't start doing this till the header install, that's why i said false knock but the more i think about it i wasn't sure if the PCM would make the car shift early if it had that much false knock or not. I'm kind of wondering if it could be the slp maf also.
05-04-2009, 01:12 AM
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I planned on doing that next weekend when he brings it back over.
One more thing i just noticed the Inj. duty cycle at WOT reaches 60% right before it shifts then drops to 20% before and after it shifts . Possible fuel pump going bad? I'm going to hook up my wideband to it also he didn't have a hole for it so i'm not sure if it's running lean yet or not. Although it did seem like it wasn't getting enough fuel
One more thing i just noticed the Inj. duty cycle at WOT reaches 60% right before it shifts then drops to 20% before and after it shifts . Possible fuel pump going bad? I'm going to hook up my wideband to it also he didn't have a hole for it so i'm not sure if it's running lean yet or not. Although it did seem like it wasn't getting enough fuel
Last edited by 89tang; 05-04-2009 at 03:32 AM.
