Mustang idles at 1,500 RPM until I stop rolling
02-07-2011, 09:15 PM
#11
5th Gear Member
Join Date: Aug 2006
Location: Central NJ
Posts: 2,158
Mine was doing this as well and I was getting 1131 and 1151 codes (I think from o-rings in the tb and when the blade is closed air is being sucked in the bad orings. I deleted my iac today by putting a copper pipe cap in the hose and hose clamped it and adjusted my tb so it idles at 800 with the set screw and the code hasn't shown up yet and idle is normal again
02-08-2011, 09:32 PM
#12
1st Gear Member
Thread Starter
Join Date: Oct 2010
Location: NC
Posts: 53
Thanks guys!
Never thought about the TB gasket, we'll hook the scanner up to it and see what codes I have. Last time I looked it was just the catalyst deficiency riff raff. Who needs cats...
The gaping hole on my spare plenum made finding the IAC pretty simple. =]
Was supposed to have gotten the IAC mod done, but it rained cats and dogs the other night, and my roommate was out of town tonight.
Never thought about the TB gasket, we'll hook the scanner up to it and see what codes I have. Last time I looked it was just the catalyst deficiency riff raff. Who needs cats...
The gaping hole on my spare plenum made finding the IAC pretty simple. =]
Was supposed to have gotten the IAC mod done, but it rained cats and dogs the other night, and my roommate was out of town tonight.
Last edited by PovertyPony; 02-08-2011 at 09:34 PM.
02-24-2011, 10:51 AM
#13
1st Gear Member
Thread Starter
Join Date: Oct 2010
Location: NC
Posts: 53
Okay, update. Yes, late I know, but college comes first and I haven't had a lot of spare time.
Turns out my care ALREADY had the IAC mod done to it, the gasket we took out had the 3/16 or 3/8" (Whatever was in the document) drill hole like the tutorial says. We cleaned everything with TB cleaner while it was out, then put it back together. They had a larger hole drilled on the other side of the gasket, so we put it in reverse to return it to a more stock state.
The funny idle symptoms ceased for about a day, and now it's right back to doing it. (High idle WHEN ROLLING, slow rev returns, stops when car finishes rolling)
The part that bothers me is that it stops when my car stops rolling, and powering the car off and on fixes it, even if it's really brief.
Also, when the motor revs, the IAC is supposed to shut, correct? We revved the motor a little with the vacuum line open, and could feel strong vacuum through the IAC when the motor was revved. Figured I'd throw that tidbit in there.
Still thinking IAC valve, or some other IAC component?
Turns out my care ALREADY had the IAC mod done to it, the gasket we took out had the 3/16 or 3/8" (Whatever was in the document) drill hole like the tutorial says. We cleaned everything with TB cleaner while it was out, then put it back together. They had a larger hole drilled on the other side of the gasket, so we put it in reverse to return it to a more stock state.
The funny idle symptoms ceased for about a day, and now it's right back to doing it. (High idle WHEN ROLLING, slow rev returns, stops when car finishes rolling)
The part that bothers me is that it stops when my car stops rolling, and powering the car off and on fixes it, even if it's really brief.
Also, when the motor revs, the IAC is supposed to shut, correct? We revved the motor a little with the vacuum line open, and could feel strong vacuum through the IAC when the motor was revved. Figured I'd throw that tidbit in there.
Still thinking IAC valve, or some other IAC component?
Last edited by PovertyPony; 02-24-2011 at 11:02 AM.
02-24-2011, 11:58 AM
#14
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
It is normal for the idle to stay higher (1000-1100 rpm) while the car is rolling, this is done to make 110% sure there is sufficient p/s fluid pressure to keep the brakes working properly and consistently.
The reason it didn't for a day was because the PCM was relearning the idle air trims after you changed the IAC flow by using the larger restriction.
The reason it didn't for a day was because the PCM was relearning the idle air trims after you changed the IAC flow by using the larger restriction.
02-24-2011, 01:05 PM
#15
2nd Gear Member
Join Date: Jan 2011
Location: Indiana
Posts: 184
My car did the exact same thing from the time I bought it (used). I just figured it was some Ford pollution crap. I did the IAC gasket trick and now have no problems at all. A lot nicer to drive. Now when I let off the gas pedal it actually slows down.
02-24-2011, 08:50 PM
#16
1st Gear Member
Thread Starter
Join Date: Oct 2010
Location: NC
Posts: 53
I understand the car idles high for legit purposes.
The reason I'm posting about it is that it's never done this before, until it randomly started doing it.
I've been driving the car 6 months, never did it once. Then it started suddenly doing it, I changed nothing. It doesn't ALWAYS do it either, it's just random. Some days it doesn't do it at all, this is why I'm baffled at what to replace. An IAC isn't cheap, for me anyways. Don't want to replace it unless I know 100% sure.
The reason I'm posting about it is that it's never done this before, until it randomly started doing it.
I've been driving the car 6 months, never did it once. Then it started suddenly doing it, I changed nothing. It doesn't ALWAYS do it either, it's just random. Some days it doesn't do it at all, this is why I'm baffled at what to replace. An IAC isn't cheap, for me anyways. Don't want to replace it unless I know 100% sure.
07-26-2011, 06:49 PM
#17
2nd Gear Member
Join Date: Oct 2007
Posts: 221
Has anyone figured this problem out for this guy cause Im having the same problems done did what you all suggested and I do have a 75mm BBK throttlebody on car. Is it possible that its a peice of crap and I need a new TB from a different company? What would cause the TB to go bad its a mechanical device with a spring working the plate open n closed.
07-26-2011, 08:32 PM
#18
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Has anyone figured this problem out for this guy cause Im having the same problems done did what you all suggested and I do have a 75mm BBK throttlebody on car. Is it possible that its a peice of crap and I need a new TB from a different company? What would cause the TB to go bad its a mechanical device with a spring working the plate open n closed.
However 1500 is too high. Have you checked the TB stop screw adjustment per this procedure? And make sure you disconnect the battery when you start the process, and if needed during the process.
With a 75mm TB you may have to close up the throttle plate a bit more than this procedure indicates...
07-27-2011, 12:25 AM
#20
2nd Gear Member
Join Date: Oct 2007
Posts: 221
Done what u said cliffy disconnected no change checked and unplugged all hoses and electrical connections to the EGR valve DPFE and AGR valves, air and electrical no CEL lights so I am still passing emissions but car will run down the street at about 1500 rpm then when I come to a complete stop it wants to almost die but then computer adjustes and brings it back 2 normal if not alittle lower idling range. Is TB Bad? If so why?