Idle speed slow to drop
Thread Starter
Intermediate
Joined: Apr 2012
Posts: 26
Likes: 2
Idle speed slow to drop
Howdy all, I have an '84 4+3, about 87k miles. Mostly stock except I ported the intake, 1.6 rockers, TPI fuel pump, advanced static timing a couple degrees, EGR delete. Had the throttle bodies cleaned, rebuilt and bushed. Runs fine for the most part, but the idle speed is very slow to drop. If I kick the throttle it'll generally come right down and settle around 800 rpm or so. But if I pull up to a stop and don't kick it, it will sit at 14-1500. If I sit long enough it'll eventually come down, but we're talking 10's of seconds. I've balanced the TBs and set TPS and idle speed per the FSM, I think I did it properly.
It's a bit of an irritant. I've watched the linkages and don't see anything hanging up or any real difference snapping it closed opposed to letting it settle gradually. It just seems like the IAC's are being lethargic for some reason unless I boot it.
Any pearls of wisdom would be appreciated!
Thanks,
Steve
It's a bit of an irritant. I've watched the linkages and don't see anything hanging up or any real difference snapping it closed opposed to letting it settle gradually. It just seems like the IAC's are being lethargic for some reason unless I boot it.
Any pearls of wisdom would be appreciated!
Thanks,
Steve
Last edited by swamp21; Aug 8, 2021 at 08:35 AM.
Thread Starter
Intermediate
Joined: Apr 2012
Posts: 26
Likes: 2
Well, I'm still having this issue and thought I'd try reposting it. I just rebalanced the TB's again, got it dialed in perfectly (hooked manometer to both TB's to finalize adjustment) but it really didn't make much difference. It doesn't take much of a kick on the throttle to bring the idle down, just a bit of a tap will do it. It's baffling.
One interesting thing I noticed tonight. When I jumper pins A & B on the ALDL connector and turn ignition on, the IAC's both cycle back and forth continuously. One of them protrudes much further into the air cavity than the other - in fact the end of the 1 pintle doesn't make it into the cavity at all - although I can see the tip of it cycling. Shouldn't these be in sync since they're not driven with independent signals? How do I do that?
Any thoughts?
One interesting thing I noticed tonight. When I jumper pins A & B on the ALDL connector and turn ignition on, the IAC's both cycle back and forth continuously. One of them protrudes much further into the air cavity than the other - in fact the end of the 1 pintle doesn't make it into the cavity at all - although I can see the tip of it cycling. Shouldn't these be in sync since they're not driven with independent signals? How do I do that?
Any thoughts?
Howdy all, I have an '84 4+3, about 87k miles. Mostly stock except I ported the intake, 1.6 rockers, TPI fuel pump, advanced static timing a couple degrees, EGR delete. Had the throttle bodies cleaned, rebuilt and bushed. Runs fine for the most part, but the idle speed is very slow to drop. If I kick the throttle it'll generally come right down and settle around 800 rpm or so. But if I pull up to a stop and don't kick it, it will sit at 14-1500. If I sit long enough it'll eventually come down, but we're talking 10's of seconds. I've balanced the TBs and set TPS and idle speed per the FSM, I think I did it properly.
It's a bit of an irritant. I've watched the linkages and don't see anything hanging up or any real difference snapping it closed opposed to letting it settle gradually. It just seems like the IAC's are being lethargic for some reason unless I boot it.
Any pearls of wisdom would be appreciated!
Thanks,
Steve
It's a bit of an irritant. I've watched the linkages and don't see anything hanging up or any real difference snapping it closed opposed to letting it settle gradually. It just seems like the IAC's are being lethargic for some reason unless I boot it.
Any pearls of wisdom would be appreciated!
Thanks,
Steve
Last edited by swamp21; Oct 20, 2021 at 10:04 PM.
