Help! New Engine Will not Idle
Help! New Engine Will not Idle See signiture for engine specs. I started it for the first time yesterday. I primed the oil pump by unplugging the coil wires and pulling the fuse to the fuel pump. I had 35 psig just with the starter. I also have a mechanical fuel pressure gauge that indicated my fuel pressure stayed around 58-60 psig. I had to give it a little gas to get it to start. It rans fine as long as I keep the RPM's up around 1000-1500. If I let off the gas it starts surging and the RPM's fluctuate between 500-1500 and it eventually dies. I do have the SES light on and I plan to have a friend with a code scanner come over today and and fight out what set the code. Like I said, it runs smooth as long as I keep my foot on the gas and keep the RPM's above 1000. Since it is a new engine, I took my PCM to LG. They made some changes in the tuning to get me through a break-in period. I plan to take the car back and they will finish tuning it.
I removed the EGR system, Air pump, PCV (replaced the oil cap with a metco breather). LG removed them from the program. If they were not removed, would the symptoms described above result? Also, I had the purge solenoid removed with the line at the intake plugged, but the line coming from the tank to the solenoid was open to atmosphere. Would this cause these idle problems.
Anyone have ideas, please reply. Thanks!
I removed the EGR system, Air pump, PCV (replaced the oil cap with a metco breather). LG removed them from the program. If they were not removed, would the symptoms described above result? Also, I had the purge solenoid removed with the line at the intake plugged, but the line coming from the tank to the solenoid was open to atmosphere. Would this cause these idle problems.
Anyone have ideas, please reply. Thanks!
TECH Resident
Joined: Jan 2002
Posts: 754
Likes: 0
From: USA
If the CAM has like a 112 LSA then it sounds like the PCM tune did not take into account the loss of vaccum at the low end and requires a retune.
With a PCM scanner see what your MAP is reporting during idle,
if it is around 45 plus KPA then the CAM is the cause and requires proper tuning.
With a PCM scanner see what your MAP is reporting during idle,
if it is around 45 plus KPA then the CAM is the cause and requires proper tuning.
Mine was an exhaust leak, didn't stall, but ran really crappy except wot. He may not have the iac programmed properly. The same thing will happen if you have an intake leak as well. The computer goes crazy trying to compensate for un metered air going into the engine. Make sure the iac is plugged in and the throttle body is tight. Good luck
On The Tree
Joined: May 2004
Posts: 133
Likes: 0
From: Dallas
After reading through your mods and your post again, I'd say your IACs are WAY off. Any idea as to what LG set your idle speeds at? Most big cams will idle around 950. Have you drilled the throttle plate at all...Have you opened the blade up with the setscrew to lower your IACs? At idle they should read between 30-50 with the AC off.
Try this...turn your car to ON...and unplug your IAC sensor. Then start your car. If the surging goes away then you know it's an IAC issue. Depending on the base tune LG gave you, you might can temporarily fix it without re-tuning by adjusting the setscrew on the throttlebody. Just keep in mind that when you do that, you'll need to do an idle re-learn. I'm sure LG will be able to fix it permanently with a proper tune later...but give that a shot.
Try this...turn your car to ON...and unplug your IAC sensor. Then start your car. If the surging goes away then you know it's an IAC issue. Depending on the base tune LG gave you, you might can temporarily fix it without re-tuning by adjusting the setscrew on the throttlebody. Just keep in mind that when you do that, you'll need to do an idle re-learn. I'm sure LG will be able to fix it permanently with a proper tune later...but give that a shot.
Trending Topics
On The Tree
Joined: May 2004
Posts: 133
Likes: 0
From: Dallas
depends on your IAC count. Like I said you want them between 30-50 at idle with the AC off. If you drill out too much, they'll be too low and then you'll be stuck with a throttle plate that's worthless. If it were me, I'd just adjust the setscrew and do an idle relearn before drilling.
Have you tried unplugging your IAC to see if the surging goes away?
Have you tried unplugging your IAC to see if the surging goes away?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
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
10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever
Verdad Gallardo I have tried anything yet other than drilling hole to 3/16. This afternoon when I get off work I will try these new suggestions and check for any vacuum leaks. If by chance I do unplug the IAC and the surging goes away, what next?
On The Tree
Joined: May 2004
Posts: 133
Likes: 0
From: Dallas
LOL, well I said it previously...but it's cool. 
I'll say it again. If you unplug the IAC and the surging goes away, then it's a problem within the tune. Your idle air tables aren't where they need to be. A temporary band aid would be to open the throttle blade up by the setscrew. This will lower your IAC counts and allow more air to enter the engine thus maintaning a more stable idle. But you have to do an idle relearn. I've had success by turning the key to ON...unplugging the IAC...turning the key off...then plugging it back in. This resets the IAC to the new TB blade position. If you don't have anything to read your IAC count like autotap, I'd unscrew the setscrew 1 full turn...then small 1/4 turns till it smoothes out.
IF by chance you unplug the IAC and the surging continues...try the setscrew trick until it stabilizes with the IAC unplugged. Once it quits turn the car off, and plug the IAC back in and fire it up. If the surge is minimal, then I'd adjust the screw 1/4 turn more and leave it.
If you end up doing over 2 complete turns with the setscrew...check for vacuum leak.
Ultimately, a good tune will remedy this problem. Unless of course it's hardware related. Btw, what's your idle speed set at?
I'll say it again. If you unplug the IAC and the surging goes away, then it's a problem within the tune. Your idle air tables aren't where they need to be. A temporary band aid would be to open the throttle blade up by the setscrew. This will lower your IAC counts and allow more air to enter the engine thus maintaning a more stable idle. But you have to do an idle relearn. I've had success by turning the key to ON...unplugging the IAC...turning the key off...then plugging it back in. This resets the IAC to the new TB blade position. If you don't have anything to read your IAC count like autotap, I'd unscrew the setscrew 1 full turn...then small 1/4 turns till it smoothes out. IF by chance you unplug the IAC and the surging continues...try the setscrew trick until it stabilizes with the IAC unplugged. Once it quits turn the car off, and plug the IAC back in and fire it up. If the surge is minimal, then I'd adjust the screw 1/4 turn more and leave it.
If you end up doing over 2 complete turns with the setscrew...check for vacuum leak.
Ultimately, a good tune will remedy this problem. Unless of course it's hardware related. Btw, what's your idle speed set at?
I want to thank everyone for the responces. I talked to Louis today and he says it can be fixed with tuning. So, Monday I plan to load the car up on a trailer and take it over to LG to get it tuned.