I'm so close, one more issue.
I'm so close, one more issue. So as some of you may know I set out to build a 6.0 forged LT1 in april of 09' after my stock lt1 lost oil pressure. I got the motor built and installed and running in october of 09' however since then ive been chasing down tiny problems left and right. Finally I have the car running good and on the road and I have one problem thats just bugging the **** out of me and I cant solve it. The car runs PERFECT when cold and after going into closed loop but when it gets to between 185-190 degrees It wont idle any more, either it will drift up to about 2k rpms and then slowly decline back to 800-1k or it will not idle at all unless I hold the pedal at 1% or more. Last night I drove the car about 10 miles, half way through the trip at a stop sign it went up to 2k rpms at idle and then settled back down. I drove maybe 1 more mile to my friends house shut the car off came back about 30 min's later and it started up and idled fine but when I left it wouldn't idle at all anymore. Even this morning in my driveway i just started it and let it idle untill warm, when it got around 190 I backed it up maybe 50 feet and it would no longer idle when I stopped, start the car back up and no idle. Let it cool and it idle's perfect. My codes right now are 1641, 1642, and 1657 which I was told is fan relays 1-2 (which are non existant) and skipshift which is obviously deleted.
Has anyone had a problem like this, Is it possible I need a bigger TB for the 20 extra cubes?
thanks guys i'm dieing to drive the car more.
Has anyone had a problem like this, Is it possible I need a bigger TB for the 20 extra cubes?
thanks guys i'm dieing to drive the car more.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
^^^
with the assumption there are no tune issues or vacumn leaks:
you need a scan tool to see what the IAC counts are. I suspect they are off and the IAC has reached its max in trying to keep the idle right after warm up. Not a uncommon problem after heads/cam builds with higher idle RPM's.
The IAC counts want to be 25-35 (32) after warm up with no AC on.
Scan first to confirm what they are but suspect them to be high. You could just crack (maybe 1/4 turn) of TB stop screw but that can screw up TPS volts which some fix by sloting TPS screw holes to slide it over some.
Better fix IMHO is to drill the small center hole between blades 1/64" bigger. DO NOT do this without first scaning the car to confirm what IAC counts are and also by checking TPS volts (.67 vdc closed & 4.5 vdc full open).
the stock hole is 1/8" and the SLIGHTEST size increase makes quite a difference in IAC readings so take BABY steps if drilling it (remove TB from car)
with the assumption there are no tune issues or vacumn leaks:
you need a scan tool to see what the IAC counts are. I suspect they are off and the IAC has reached its max in trying to keep the idle right after warm up. Not a uncommon problem after heads/cam builds with higher idle RPM's.
The IAC counts want to be 25-35 (32) after warm up with no AC on.
Scan first to confirm what they are but suspect them to be high. You could just crack (maybe 1/4 turn) of TB stop screw but that can screw up TPS volts which some fix by sloting TPS screw holes to slide it over some.
Better fix IMHO is to drill the small center hole between blades 1/64" bigger. DO NOT do this without first scaning the car to confirm what IAC counts are and also by checking TPS volts (.67 vdc closed & 4.5 vdc full open).
the stock hole is 1/8" and the SLIGHTEST size increase makes quite a difference in IAC readings so take BABY steps if drilling it (remove TB from car)
how about a bad Eng. Sensor fuse? I never knew that the reverse lockout was connected to that also? fixed all my problems now i can actually back up, and when I stop the car doesn't die and my skipshift code is gone, twas a good day for only costing $.50 haha, thanks for the help guys, car runs amazing now.
still running on a trifecta mail order tune. I have a few more things I need to fix before bringing it to the dyno (header leak, coolant leak out of home made steam crossover etc) but it runs damn good. Im not really expecting big numbers being that its on port matched stock heads and low compression with the xfi280 which needs more air and higher comp. But its getting boost next so that should solve that problem 
I can take an idle vid if you want? it sounds pretty nasty at idle
I can take an idle vid if you want? it sounds pretty nasty at idle
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote just a blown fuse, look in the under hood box, on the drivers side fender well. On the passenger side (of the box) their should be 4 fuses lined up, its the second one from the front. 20A fuse and I believe it runs: o2 heater circuits, 2-3 gear lockout circuit (skipshift), reverse lockout circuit, maf control and Automatic park lockout (for auto's) And maybe it runs one other thing also. So if you have skipshift code PO1657 like I did and your car wont idle sometimes and you have to wedge your back against the door to get your car in reverse then change that fuse and have a nice day lol.
