Gary98Z

iTrader: (9)

My idle/surge problems were all t/b related. When I went back to stock, it cured 99% of my problems.

Have you checked the idle adjustment screw on the stock t/b? Maybe the previous owner increased it.

Good luck.

Gary

shoemike

iTrader: (25)

i had this problem when my car was "professionally " tuned,
and it was solved when i bought EFILive and went through the RAFIG process.

kelp

I put a 100 mm TB on my LS7. I cut my Idle startup Airflow and Final Idle Airflow controlled nicely - it required reducing the values a whopping 65+% down (!)

Now it hangs at low driving speed for a couple of secs...at 3-4000 RPM! Quite a hang. It will also accelerate to those RPMs if clutch engaged.

Here's what it's NOT:
- PE, Hot PE, etc.
- Any of the timing tables, idle, coastdown, main spark, etc.

Seems to help:
Reducing the MAF table. But this is no way to do it and it starts and runs like crap by the time I correct it enough.

I'm trying this:
Final Idle Airflow Minimum, over 2000 RPM. Not only leveling this off (made no difference), but decreasing it so the whole curve goes DOWN not UP like normal. I'll try that tomorrow.

Anything else?

Goldfinger911

iTrader: (24)

Have you logged data and determined exactly where the additional idle airflow is coming from? IAC? Throttle blade position? Throttle follower? Throttle cracker? Does your TPS show 0% throttle when you let off the gas? If you have determined that the mechanics of the throttle system is okay, then without some data... you are pissing up a rope.

When the idle hangs... pull over, pop the hood and jump out and see if the throttle cable is tight or loose. It tight... it is probably a mis-adjusted cable, or the TCS system ( if you have it) If it is not tight, then physically make sure the throttle is closed to the stop. If not, then it is binding. If it is closed to the stop, it is time to look at the data on the source of the airflow.

Just making changes to different tables without data to back it up is worse than doing nothing.

phantazn

iTrader: (7)

sounds like the same problem i have. while the car is moving itll idle at 1600+ until i slow down and stop, then it will drop to 1100 for a second before settling down at 800. on occasion it will fix itself after some driving, only to reappear again the next time i start the car. this is on a bolt on car with stock tune, and the problem developed recently with no additional work done for months prior.

WS6nJAX

iTrader: (207)

i know this is what everone thinks, but there has been countless hours spent by a couple tuners who are extreamly good at what they do, are really good friends and i completey trust. i started this thread to simply see if anyone has had a similar problem and it be something other than tune related.

please keep in mind that when using the efi live a road-runner was also used thus (i am not a tuner, just a wrench turner so please correct me if i am wrong here) starting with a stock tune and removing any issues that would be related to a tunning problem in the cars pcm. even with this, the problem continued. the idle hangs until exactly 10 mph.

BlueZ35th

iTrader: (8)

if im at the track the only time i noticed a hang in RPM is when i'd do a burnout, it'd hang from 16-24. till i staged and let it sit quick.

tee-boy

iTrader: (8)

when it hangs, can you put your foot underneathe the accelrator pedal and pull it out towards you? Mine does this, and I can make it idle down by pulling out the pedal. Which leads me to believe the TB blade is getting stuck.

Goldfinger911

iTrader: (24)

You have been given all the steps in this thread to troubleshoot this problem and determine the cause. EFILive was used? Post your tune and and driving logs you have.

kelp

This is an LS7. It is fly-by-wire. There is no Throttle follower, no Throttle cracker. Datalogs confirm what I stated. So, here's your rope back.

Using the same methodology, I investigated this further.

Further analysis using the 12 variables of the two rheostat sensors of the 100 MM TB and the LS7 stock TB reveals these use rheostats are substantially different. Without going into detail, this is responsible for the differing in airflow control patterns I related previously.

Lastly, this appears to be an isolated incident. It is similar in presentation, but arises from a different cause. I wanted to be sure to follow up my initial post with my findings to preserve clarity of the original poster, and this thread. Thanks to everyone for your input.

Goldfinger911

iTrader: (24)

Haha. Thanks for the rope. Actually, I should have been more clear with a quote... I wasn't replying to you sport, I was replying to the original poster of the thread. I didnt read everyone elses post on the bandwagon. Sorry bro.

bomb3r13

iTrader: (2)

I had a similar problem once with my car. I thought it was tune related since the RPM would hang obnoxiously high when cruising and idling the engine past 5-10mph sometimes and calm down when I stopped. On my problem it ended up being an electrical problem with my battery. I just tightened the connectors and it got rid of the problem completely.

WS6nJAX

iTrader: (207)

this is the direction i am leaning. something elec or sensor related. so far nothing i can find.


appreciate all the info, but as i already confessed, i am no tuner. thus, i have no tune or logs to post.

thought about that. i have even used a voltmeter to monitor the tps and all is well on that end. 9mph and under its fine....10mph and over it hangs.

Schwanke Engines

iTrader: (1)

I know you don't want to hear it, but it does sound like a tune issue. If you want, you could have your guys send me the tune to look over. Never hurts to have more eyes look things over.

Goldfinger911

iTrader: (24)

The throttle cable floats in the end of the gas pedal rod, therefore if you pull the pedal toward you and the idle drops it isnt a problem with the throttle blade, it is a problem with the pedal itself. (tough to push a cable)

WS6nJAX- have you tried any of the other suggestions in this thread so as to pinpoint where the hanging idle is occurring? If everything is mechanically fine then it is your tune. Good tuner or not, it is not hard to accidentally overlook something.

I had a hanging idle/throttle problem when I bought my car and everyone said it was my 90mm TB. Turned out it was my TCS motor not allowing the TCS pulleys to release the throttle completely, even with TCS turned off. My point is, you never know until you break it down in parts and troubleshoot properly.

Ask you tuner for your tune file. There are lots of people on this site and other that would look it over and give you ideas.

josepy121380

iTrader: (21)

this happens to mine also. but once i press the clutch in it goes back to normal.

cleatus99

I have same problem 2001 T/A WS6 ALL STOCK Original, no retuning etc.

it'll happen to me when I'm coating down the hill in Neutral with Clutch out......

Goldfinger911

iTrader: (24)

https://ls1tech.com/forums/pcm-diagnostics-tuning/865850-letting-off-gas-car-seems-idle-high.html

jattgunman

iTrader: (1)

Minedid something similar and I couldnt figure out for the longest time but Iunhooked the tsp connector from the throttle body and it had a bunch of oil in it which I cleaned out and after that, it worked perfectly

foshizl

I dont know what kind of intake you have, but my egr hose on the top of the intake was leaking and it was causing hanging idle on my car...