New idle problem.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 233
Likes: 0
New idle problem.
From a cold start when I crank the Vette it starts right up. It then will idle assume with a choke at 1000rpm then it will settle down to 700/600rpm.
Lately it has been the same except after driving about 20 minute or so the idle creeps back up. In drive at idle it's 800 when shifted back into park it's at 1000?
When I first inherited the car last year I changed the TPS and the IAC valve. THe car was having a horrible surging high idle back then. Turned out to be the ECM. Had the ECM replaced and it has been fine ever since. That is until now. Any ideas?
Lately it has been the same except after driving about 20 minute or so the idle creeps back up. In drive at idle it's 800 when shifted back into park it's at 1000?
When I first inherited the car last year I changed the TPS and the IAC valve. THe car was having a horrible surging high idle back then. Turned out to be the ECM. Had the ECM replaced and it has been fine ever since. That is until now. Any ideas?
Racer
Joined: Nov 2010
Posts: 460
Likes: 1
From: Oliphant Ontario
Your cold start sounds right on the money, no choke though, IAC gives it more idle until it warms a bit.
Make sure of a couple of things, the tach is accurate (mine shows 1000rpm when Datamaster says 650). Make sure your throttle cable isn't tight or something else causing the actual throttle plates themselves to slightly open once warmed up. You'll see the base idle screw on the drivers side of the linkage. At _all_ times except when you push the peddle it should be tight against the linkage stop. If at any time you can even put a playing card in there, something is binding.
Could also be a vacuum leak from intake or something that doesn't show up until engine is hot? When it's idling high and you turn it off and restart what's it do? If it goes up higher still then settles down in 2 seconds to what seems like 1000rpm then the IAC is still functioning.
Make sure of a couple of things, the tach is accurate (mine shows 1000rpm when Datamaster says 650). Make sure your throttle cable isn't tight or something else causing the actual throttle plates themselves to slightly open once warmed up. You'll see the base idle screw on the drivers side of the linkage. At _all_ times except when you push the peddle it should be tight against the linkage stop. If at any time you can even put a playing card in there, something is binding.
Could also be a vacuum leak from intake or something that doesn't show up until engine is hot? When it's idling high and you turn it off and restart what's it do? If it goes up higher still then settles down in 2 seconds to what seems like 1000rpm then the IAC is still functioning.
Last edited by Sandpiper59; Feb 19, 2011 at 08:08 PM. Reason: typo
Thread Starter
Instructor
Joined: Sep 2007
Posts: 233
Likes: 0
Your cold start sounds right on the money, no choke though, IAC gives it more idle until it warms a bit.
Make sure of a couple of things, the tach is accurate (mine shows 1000rpm when Datamaster says 650). Make sure your throttle cable isn't tight or something else causing the actual throttle plates themselves to slightly open once warmed up. You'll see the base idle screw on the drivers side of the linkage. At _all_ times except when you push the peddle it should be tight against the linkage stop. If at any time you can even put a playing card in there, something is binding.
Could also be a vacuum leak from intake or something that doesn't show up until engine is hot? When it's idling high and you turn it off and restart what's it do? If it goes up higher still then settles down in 2 seconds to what seems like 1000rpm then the IAC is still functioning.
Make sure of a couple of things, the tach is accurate (mine shows 1000rpm when Datamaster says 650). Make sure your throttle cable isn't tight or something else causing the actual throttle plates themselves to slightly open once warmed up. You'll see the base idle screw on the drivers side of the linkage. At _all_ times except when you push the peddle it should be tight against the linkage stop. If at any time you can even put a playing card in there, something is binding.
Could also be a vacuum leak from intake or something that doesn't show up until engine is hot? When it's idling high and you turn it off and restart what's it do? If it goes up higher still then settles down in 2 seconds to what seems like 1000rpm then the IAC is still functioning.
Thank you for this. When I re-start the car it rises or stays at 1000 and then goes back down to 800.
