LS3 525hp crate engine high idle
Thread Starter
Teching In
Joined: Jun 2018
Posts: 39
Likes: 1
From: Deerfield WI
LS3 525hp crate engine high idle Looking for some ideas. I have a crate engine ls3 with the gm wire harness for the engine. When i started the engine for the first time everything ran fine idle was fine. Now that I have been test driving the car i now get a cel for idle air control for high idle. It now idles at 975rpm and when i drive it the idle is erratic. It has died once and it also has idled at 2000rpm. I had open headers on it and have since added 2 feet of exhaust on it as i had read that that can cause erratic idle. The engine is in a 35 chevy coupe and has a tremec 6 speed in it. When i first drove it i had a master cylinder issue and have since put a new one in it and brakes seem to be fine. I have since replace the hose from the pcv and also the one to the brake booster. I can't seem to find a vacuum leak that would cause the high idle and cel. Is it possibly the brake booster, or am i missing something else? any help would be much appreciated I am trying to get this fixed so i can take it to the shop to have a ss exhaust put on
I would say to turn the idle down with the adjustment screw if drive by cable because the throttle body blade may be opened too much. Do you have HP Tuners so you can do some logging to see what your IAC counts are at idle?
Thread Starter
Teching In
Joined: Jun 2018
Posts: 39
Likes: 1
From: Deerfield WI
i disconnected the line on the booster and put a bolt in it, same result i also tried very carefully some starting fluid before it got warm around the intake to see if the rpms would raise to show me where the leak might be and nothing
Thread Starter
Teching In
Joined: Jun 2018
Posts: 39
Likes: 1
From: Deerfield WI
No I haven't but i will check over I was careful with installing it and the harness is well loomed to protect them. I'm going to try to talk to a gm tuner my friend knows tomorrow and see if he has some ideas also
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TECH Apprentice
Joined: Oct 2018
Posts: 336
Likes: 85
From: Glendale, AZ
My neighbor was having some idle problems, was a leak in the intake. Spraying wasn't enough to catch the leak by seeing the idle smooth up, but it did show up on hp tuners via the stft's. May need to see if someone has it around you. Need more data.
What sort of throttle body setup are you running? I think in this case you will need to seek a reputable tuner to take a look at your setup. At the very least they can shine some light on the problem area usually.
Well.....consider that this dude ain't been on the forum since June.....but that said, he's running a crate GM engine with all OEM LS3 parts except that the engine has the GM ASA cam instead of the stock LS3 cam; and maybe upgraded valve springs.
Since you asked.
KW
Since you asked.
KW
Well darn lol. I fell victim to the oldest forum tricks in the book.
TECH Enthusiast
Joined: May 2008
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From: Carnation, WA
