The 02 sensor giving bad readings could cause a random change in the Air/Fuel mixture causing the problems your having..WW
Intermitent Low Idle - Stall
Thread Starter
Racer
Joined: Mar 2004
Posts: 252
Likes: 1
From: Troy Illinois
Intermitent Low Idle - Stall
Last year I replaced my intake manifold and runners with Edelbrock units. After completion I had an intermitent low idle/stall. I replaced the IAC but this did not help. This year I removed the runners to port the plenum and reassembled eliminating the EGR valve, thinking this would eliminate the intermitent low idle and installing a new 52mm Throttle Body. Still having the same problem. Most of the time it goes to idle fine when stopping but once in a while the idle will go up and then down and it may stabilize or it may stall. If I give it a little gas then slowly release the throttle the idle may stabilize. Any thoughts where to look next?
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Does the idle condition change when the engine is cold vs warm vas hot(up to temp)?
Assuming there are no fueling or vacuum leak complications.....after market TB may require the TB throttle stop screw adjustment, IAC reset and throttle positon sensor voltage adjustment to attain your desired idle.
Other options:
Tuning software such as Tunerpro RT (freeware) (year specific bin file to access prom data/ connection data cable is also needed) allows you to see your IAC steps, fuel/02 readings and a bunch of other stuff that may help you narrow down the issue as well.
Assuming there are no fueling or vacuum leak complications.....after market TB may require the TB throttle stop screw adjustment, IAC reset and throttle positon sensor voltage adjustment to attain your desired idle.
Other options:
Tuning software such as Tunerpro RT (freeware) (year specific bin file to access prom data/ connection data cable is also needed) allows you to see your IAC steps, fuel/02 readings and a bunch of other stuff that may help you narrow down the issue as well.
Thread Starter
Racer
Joined: Mar 2004
Posts: 252
Likes: 1
From: Troy Illinois
Thanks for the ideas. Had same idle problem before I changed to the 52mm TB. I am using the same IAC and TPS as I was using on the stock TB. As I mentioned before the IAC is new. If I had a vacuum leak wouldn't there be a constant idle problem. I haven't noticed the problem untill the car has warmed up. I will check ECM outputs using Winaldl. All help is appreciated!
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
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St. Jude Donor '09-'10, '14
Instructor
Joined: Jul 2008
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Mine is doing something like that too. Recently replaced the O2 sensor (the IAC was replaced last year, would just die at stops when warm, fixed it). Also replaced the EGR temp sender. Mine alwasy idled at about 7-800, slightly high but never a problems. I just did the O2 and EGR temp sender (to get rid of check engine light at speed) got everything running great (even think the o2 sensor increased my milage) but now when 100% warm at some stops it will idle down to 3-400 rpm and almost die. It comes back to 5-600 "almost" all the time.. but its really concerning when in heavy traffic thinking you are going to die at every stop. I'm guessing I need to do the Idle set up thing... wish I was better with voltmeter.
4th Gear
Joined: May 2015
Posts: 4
Likes: 0
From: Redding, CA
John
I am having a similar problem.
my '87 Vette had idled fast since I bought it 4 years ago.
It idles at 10K +/- stopped and in gear. If I kick it out of gear it goes to 14K +/- and then slowly drops to 10 to 11K.
It set for three plus years while I repainted and redid the interior. I ran it regularly to keep it warm but it was not driven.
when I put it back on the road I put Rislone injector cleaner in it to make sure their was not varnish or fouling.
It began to occasionally idle down to 6 to 8K in gear at stops.
Now it will intermittently idle at 12 to 13 K or idle so slow it dies.
Their is no set length of time or temperature for it to run slow or fast.
Ideas?
my '87 Vette had idled fast since I bought it 4 years ago.
It idles at 10K +/- stopped and in gear. If I kick it out of gear it goes to 14K +/- and then slowly drops to 10 to 11K.
It set for three plus years while I repainted and redid the interior. I ran it regularly to keep it warm but it was not driven.
when I put it back on the road I put Rislone injector cleaner in it to make sure their was not varnish or fouling.
It began to occasionally idle down to 6 to 8K in gear at stops.
Now it will intermittently idle at 12 to 13 K or idle so slow it dies.
Their is no set length of time or temperature for it to run slow or fast.
Ideas?
