Low Idle
10-25-2012, 01:36 PM
#1
2nd Gear Member
Thread Starter
Join Date: Jul 2011
Location: Indiana
Posts: 414
Low Idle
I've done some research, and most say a manual 4.6 will idle around 800 rpm after it has warmed up. Mine tends to idle around 600 rpm, and it's just a tad shaky. I've replaced the IAC and cleaned the MAF. What else would be worth looking at? Might be worth noting the previous owner installed an aftermarket TB.
10-25-2012, 03:31 PM
#2
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Check the throttle stop screw preset (here's how), but: disconnect the battery for 5 to 7 minutes before doing so, then let the engine idle for 15 minutes before proceeding with the adjustment.
This will clear the Keep Alive Memory (KAM) and let the PCM attempt to learn new idle air and fuel trims before you proceed. I.e. get to a known starting place...
This will clear the Keep Alive Memory (KAM) and let the PCM attempt to learn new idle air and fuel trims before you proceed. I.e. get to a known starting place...
10-25-2012, 06:45 PM
#3
2nd Gear Member
Thread Starter
Join Date: Jul 2011
Location: Indiana
Posts: 414
Nice article, I'll give it a try this weekend. If nothing else it's free, better than throwing parts at it. Any chance that may also have something to do with the car cranking but not starting every now and then? Possibly not getting enough air in at startup sometimes? Probably not, but it would be great to kill 2 birds with 1 stone.
Last edited by jrp1588; 10-25-2012 at 06:47 PM.
11-24-2012, 10:16 AM
#4
2nd Gear Member
Thread Starter
Join Date: Jul 2011
Location: Indiana
Posts: 414
I finally got around to piddling with the stop screw, haven't done the full process, but I did open it up a smidge. I haven't allowed it to warm up to see if it helped things, I figure as easy as it was, I'll just nudge it a bit after driving it a few times till I get it where I want it.
One thing I noticed, my stop screw doesn't have a locknut. I imagine this is what allowed it to get out of adjustment in the first place. It's a BBK 70mm, not sure if they came that way or the previous owner removed it for some reason. I guess I need to go to the hardware store and buy some nuts and see what fits.
One thing I noticed, my stop screw doesn't have a locknut. I imagine this is what allowed it to get out of adjustment in the first place. It's a BBK 70mm, not sure if they came that way or the previous owner removed it for some reason. I guess I need to go to the hardware store and buy some nuts and see what fits.
11-24-2012, 11:55 AM
#6
2nd Gear Member
Thread Starter
Join Date: Jul 2011
Location: Indiana
Posts: 414
IAC has been changed, TPS hasn't been messed with, so I suppose that is possible, and as far as I know the ECU it untouched. I haven't had it tuned, though I suppose the PO could have.
Wouldn't vacuum leaks make it idle higher?
Wouldn't vacuum leaks make it idle higher?
11-24-2012, 11:58 AM
#7
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
controlled idle to boot.
I would put a lock nut on it--most are M5 x 0.8...
11-24-2012, 12:21 PM
#9
2nd Gear Member
Thread Starter
Join Date: Jul 2011
Location: Indiana
Posts: 414
Well I spent some more time with it. I've moved the adjustment screw out a good bit. It's opened at least a full ture more than it was before, and it's still idleing exactly how it was before.
I feel like if anything I'm just making it worse. Also I'm chewing up the threads on the screw pretty badly using adjustable pliers to turn it. Is there a better way to turn it?
Edit:cancel that, I gave her another half turn and that put me right around 800rpm idle and eliminated most of the vibration I was experiencing. I think I will pick up a nut to keep it at the proper adjustment though. Does it need to be an actual locknut with the nylon in it or just any old nut? From your picture it just looks like a regular nut.
I feel like if anything I'm just making it worse. Also I'm chewing up the threads on the screw pretty badly using adjustable pliers to turn it. Is there a better way to turn it?
Edit:cancel that, I gave her another half turn and that put me right around 800rpm idle and eliminated most of the vibration I was experiencing. I think I will pick up a nut to keep it at the proper adjustment though. Does it need to be an actual locknut with the nylon in it or just any old nut? From your picture it just looks like a regular nut.
Last edited by jrp1588; 11-24-2012 at 12:36 PM.
11-24-2012, 12:42 PM
#10
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Well I spent some more time with it. I've moved the adjustment screw out a good bit. It's opened at least a full ture more than it was before, and it's still idleing exactly how it was before.
I feel like if anything I'm just making it worse. Also I'm chewing up the threads on the screw pretty badly using adjustable pliers to turn it. Is there a better way to turn it?
Edit:cancel that, I gave her another half turn and that put me right around 800rpm idle and eliminated most of the vibration I was experiencing. I think I will pick up a nut to keep it at the proper adjustment though. Does it need to be an actual locknut with the nylon in it or just any old nut? From your picture it just looks like a regular nut.
I feel like if anything I'm just making it worse. Also I'm chewing up the threads on the screw pretty badly using adjustable pliers to turn it. Is there a better way to turn it?
Edit:cancel that, I gave her another half turn and that put me right around 800rpm idle and eliminated most of the vibration I was experiencing. I think I will pick up a nut to keep it at the proper adjustment though. Does it need to be an actual locknut with the nylon in it or just any old nut? From your picture it just looks like a regular nut.
Did you do the complete adjustment process, using the 0.010" feeler gauge and then tightening the nut 1 turn?