High idle
- Thread starter scskydivin
- Start date
scskydivin
SCCoA Member
Wow Dave!
You rock man!!!
Your extensive knowledge of our cars continues to astound me. I will print this and take it outside with me while I conduct these tests. You've givin me walk through instructions. I'll let you know how it goes. I may be buying that BBK from you yet.
I know your time is valuable.
Thank You.
You rock man!!!
Your extensive knowledge of our cars continues to astound me. I will print this and take it outside with me while I conduct these tests. You've givin me walk through instructions. I'll let you know how it goes. I may be buying that BBK from you yet.
I know your time is valuable.
Thank You.
XR7 Dave
Registered User
here it is in summary form...
with engine at warm idle, unplug IAC valve connector and see if engine stays running, if it does then you need to find out where its getting air from
/done
Yes well I've been known to get carried away with my explanations,
. My local friends know that when I say "You see it's like this...." then they are in for a long story. here it is in summary form...
with engine at warm idle, unplug IAC valve connector and see if engine stays running, if it does then you need to find out where its getting air from
/done
Actually, if the car stalls out when you do this then the TB is not set up properly. The engine should drop about 150 or so rpm without the IAC and still be able to idle. Once the motor can do this, then plugging the IAC back in should put the IAC duty cycle back to around 30% which is bang on where it should be at hot idle.
Its a deliberate fail safe just in case the IAC dies so you can at least still drive the car to the garage etc for repairs.
Fraser
scskydivin
SCCoA Member
This morning while the kiddos were eating their morning rations of Honey Nut Cheerios, I started the bird up. It sat all night so it was good n cold. Idle jumped to 1600, stayed there for 5 seconds and worked it's way down to 1000 rpm's over 3 or 4 seconds and stayed there. I pulled the IAC plug, no change in idle at all. plugged it back in, nothing. I did this 4 times with the same result. It was like the IAC wasn't there at all.
Smoke test is scheduled for 7am Saturday morning at Dobbs...
You'll find a vacuum leak. Or you may not find it, but you have one
The IAC bleeds air in at idle to keep the car idling, but your car doesn't need that bleed, it's getting enough air from somewhere. So disconnecting the IAC has no affect.
RwP
Rezid
Registered User
I've been following this thread and i'm having the same problem as you scskydivin. starting my bird up cold idles at around 1400 rpm then slowly drops to 1000 and stays there. I unpluged the IAC connector yesterday and only noticed a 200 rpm drop. plugged it back in and went back up to 1000. Its been difficult trying to locate this vacuum leak....
JeepsterSC
Registered User
Do thottle bodies wear out? I've backed the set screw all the way out so that the arm is sitting on the metal part were the screw extends from and the plate does not stick as Dave described in his post.
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David Neibert
SCCoA Admin
Ray,
Before going in for the smoke test, suggest pulling the IAC off and putting some duct tape over the two holes on the throttle body to see if that corrects the high idle problem.
David
XR7 Dave
Registered User
Throttle bodies do not wear out. A throttle body could wear out if the shaft rotated in a bushing or just through the aluminum body like a carburetor, but the TB's use a sealed ball bearing on the shaft so that there is no wear point. However, the "sealed" ball bearings have been known to leak, some moreso than others.
XR7 Dave
Registered User
If you are still having issues with high idle after setting the TB as described and verifying that you do not have any leaks, then the rest is tuning.
scskydivin
SCCoA Member
Ok David, I'll try that.
scskydivin
SCCoA Member
Ok guys,
Got the smoke test done over at Dobbs this morning. The guys hooked the smoke machine up to the vaccum nipple on the front of the MP inlet plenum. It instantly revealed 3 leaks. One at the PCV valve where it goes into the valve cover. I've gotta put a clamp on it. (I know Mr. Neibert, always zip tie everything) Another one behind the inlet plenum, one of the hard plastic vaccum lines snapped off, that one probably being the biggest issue. And the 3rd one was at the PP throttle body. It's leaking where the linkage snaps onto the TB shaft. So, tomorrow, I'll fix #'s 1 & 2. I don't know if the throttle body only leaked during the smoke test and'll be fine when it's drawing air or not. I'm not sure if it's an easy fix or if I have to replace the throttle body itself.
Got the smoke test done over at Dobbs this morning. The guys hooked the smoke machine up to the vaccum nipple on the front of the MP inlet plenum. It instantly revealed 3 leaks. One at the PCV valve where it goes into the valve cover. I've gotta put a clamp on it. (I know Mr. Neibert, always zip tie everything) Another one behind the inlet plenum, one of the hard plastic vaccum lines snapped off, that one probably being the biggest issue. And the 3rd one was at the PP throttle body. It's leaking where the linkage snaps onto the TB shaft. So, tomorrow, I'll fix #'s 1 & 2. I don't know if the throttle body only leaked during the smoke test and'll be fine when it's drawing air or not. I'm not sure if it's an easy fix or if I have to replace the throttle body itself.
XR7 Dave
Registered User
Did you have the bypass valve open when doing the smoke test? Sorry probably should have mentioned that. The only way smoke can get into the IC trac is via the bypass valve. But you may have found your biggest leaks. The throttle shafts always leak on those TB's. In fact nearly all TB's will leak at the shaft but some are worse than others. One guy on here I recall used something to seal up his throttle shaft but I don't remember what it was.
scskydivin
SCCoA Member
I clamped the PCV hose. I also replaced the broken plastic vaccum lines with vaccum hose. The broken lines were from the EGR to the tree on the wiper motor bracket. And another broken line from that tree to the fire wall. Yes, David N, I zip tied them both (With color coded ties!). I started the car and the idle was as follows:
initial start up 1600
in gear 1100
After driving 3 miles around the house, I didn't have to touch the gas petal at all. Was still going 45 mph down Watson Rd. So, basically the same thing.
With the car in park, in the driveway, I'd bump the idle to 2000. It'd stay there for 4 seconds then fall to 1100. Over the next minute it'd settle to 1050 and stay there. In gear, it's at 650 and still pulling at a good clip.
initial start up 1600
in gear 1100
After driving 3 miles around the house, I didn't have to touch the gas petal at all. Was still going 45 mph down Watson Rd. So, basically the same thing.
With the car in park, in the driveway, I'd bump the idle to 2000. It'd stay there for 4 seconds then fall to 1100. Over the next minute it'd settle to 1050 and stay there. In gear, it's at 650 and still pulling at a good clip.
I did not have the bypass valve open during the smoke test, nor did I notice the shop having it open either. However, today I noticed the bypass valve on the return plenum was wide open during idle. I pulled the valve closed and got no change in idle rpm's. It was very intent on being wide open, by the way, as holding it closed was difficult. Upon sutting the engine off, it closed up.
scskydivin
SCCoA Member
Doing that now, Coach.
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scskydivin
SCCoA Member
Ok, I set the TB as you instructed. I backed the adjusting screw off until it wasn't touching the throttle arm. The engine did continue to run without a problem. So I'm sure there's still a leak somewhere.
The rpm's have come down quite a bit. At idle the rpm's are at 650 in park, and 625 in gear. I bumped the rpm's up to 2000. Immediatly dropping down to 800. Not a half second later it's at 650. I took it for the same drive around my neighborhood. It was remarkably different. The thing actually drove the way it's supposed to. No taking off from the stop light without the accelerator. No riding the brakes all the way down the street to keep from going 45 mph. And, as a bonus, It's quiet again!
It's running just as good as it was when you tuned the car last time you were here. I will go back to Dobbs next weekend to smoke it with the bypass valve open. Maybe that will shed some more light on this issue for me.
Thanks for all your help.
The rpm's have come down quite a bit. At idle the rpm's are at 650 in park, and 625 in gear. I bumped the rpm's up to 2000. Immediatly dropping down to 800. Not a half second later it's at 650. I took it for the same drive around my neighborhood. It was remarkably different. The thing actually drove the way it's supposed to. No taking off from the stop light without the accelerator. No riding the brakes all the way down the street to keep from going 45 mph. And, as a bonus, It's quiet again!
It's running just as good as it was when you tuned the car last time you were here. I will go back to Dobbs next weekend to smoke it with the bypass valve open. Maybe that will shed some more light on this issue for me.
Thanks for all your help.
David Neibert
SCCoA Admin
Ray,
Did you ever try removing the IAC valve and duct taping the ports closed ?
David
Did you ever try removing the IAC valve and duct taping the ports closed ?
David