Fast idle after intake mod

Topic: Fast idle after intake mod (Read 9376 times) previous topic - next topic

Fast idle after intake mod

Reply #75 – February 17, 2014, 09:06:11 PM

If you can kill it by plugging the iac hole, you should be golden. I'm leaning to a bad iac. is it possible you installed it upside down?

Unplug the iac with it running. lower idle until the car lugs and then plug it back in. if it idle fine after, your fine. it might be possible the iac is bad or getting stuck high. id be willing to bet your problem lies with your iac as long as your not throwing any other codes.

Fast idle after intake mod

Reply #76 – February 17, 2014, 09:43:37 PM

Just wondering but have you hooked up a tach/dwell meter to see what the engine is really idling at? The reason I ask is that if your Thunderbird has a full digital dash the tach display could be waaay off. For example at hot idle my Thunderbird idles right at 750rpm in park and 65rpm in drive with the parking brake on (both settings are within factory specs). Now those rpm readings are from a tach/dwell meter. The tach on the digital dash displays 5 bars at idle (800-1000rpm) when the actual rpm is about 250rpm lower. The factory buttstuffog tachs aren't much better. The tach in my Mark VII shows about 900rpm at hot idle. It's really at 700rpm according to a tach/dwell meter. The only way to know what rpm your Thunderbird's engine is actually idling at is to hook up a tach/dwell meter and find out. Once you've got a tach/dwell meter hooked up do a base idle reset: http://sbftech.com/index.php/topic,1031.0.html
Take a look at page two in the link. It describes the exact situation I'm talking about.

Fast idle after intake mod

Reply #77 – February 18, 2014, 06:13:09 AM

Whatever you find, don't leave that RTV in the intake. You should never allow RTV in the air and fuel delivery systems or in the exhaust upstream of the oxygen sensors, as the silicone will wreck your O2s.

Fast idle after intake mod

Reply #78 – February 18, 2014, 08:59:32 AM

again, use a short vac hose and place it on the egr fitting, with your mouth put suction on the vac line then see if it holds vac. .. or use your vac guage, i think you said you got one of those.

the cruse cable is easy to fix ,, later though.
reason for mentioning it as well as the gas pedal / transmission line is the routing of these three things is important to watch over. if there are too sharp of bend ect, the gas pedal or cruise cable will not move easy and help prevent the TB from closing.

sounds like you have a modifed pcv connection.
there is a plastic bushing down in the lower intake and whatever the PO did, may be working well or not,, seems your ok with it.

did you ever inspect the vac tree for a cracked port?

Fast idle after intake mod

Reply #79 – February 18, 2014, 08:59:55 AM

Fast idle after intake mod

Reply #80 – February 18, 2014, 04:44:11 PM

Quote from: Haystack;429063

If you can kill it by plugging the iac hole, you should be golden. I'm leaning to a bad iac. is it possible you installed it upside down?

Unplug the iac with it running. lower idle until the car lugs and then plug it back in. if it idle fine after, your fine. it might be possible the iac is bad or getting stuck high. id be willing to bet your problem lies with your iac as long as your not throwing any other codes.

He already established that the bleed hole is LARGER!!! on the new TB. As far as the EGR holding vacuum that does nothing because if the diaphragm is blown the EGR wont open. And there is no VACUUM at the valve when the engine is at closed THROTTLE !!! The mounting gaskets and cooler adapter should be checked for corrosion and proper gaskets sealing correctly. He also posted that the throttle blade was in fact closing all the way.

I find it fascinating how installing an IAC UPSIDE DOWN would cause this as that is beyond comprehension as he totally blocked it off with a blank gasket!!!!! Just wondering how many IAC troubles you have addressed in your career STACKS. Better think over what you just posted!!!!!@

Stacks your post is fascinating because he clearly can not drop his idle with the IAC DISCONNECTED. HELLO if he could do this he would not be having a problem !!

QUESTION what would an upside down IAC motor DO as we sometimes mount them differently on different applications and also remotely. Guess you did not read my post on BLUEPRINTING THE IAC you should take the time and read it it is quite informative stacks!!

Here you go one of my IAC motors being broken down for blueprinting!!!

Fast idle after intake mod

Reply #81 – February 18, 2014, 04:50:31 PM

Normally i use the MIG to tack those holes closed. Once you close that hole off all your idle parameters will fall in to place. Those holes control the bypass air and there size is critical as you found out. A slight difference in diameter is very critical when it brings the idle circuit parameters out of speck. Remember once the IAC removes all the bypass air and the idle is to high the ECM and IAC are out of the equation. Some people use a steel rivet then tap out the center. But remember if it gets loose the part goes right in the engine. AND THAT IS NOT GOOD!!!

Fast idle after intake mod

Reply #82 – February 18, 2014, 05:31:39 PM

Also FORD guys should have a selection of these or an adjustable spacer plate. This is all part of tuning the IAC PROPERLY!!!

Fast idle after intake mod

Reply #83 – February 18, 2014, 08:32:30 PM

Quote from: thunderjet302;429066

Just wondering but have you hooked up a tach/dwell meter to see what the engine is really idling at? The reason I ask is that if your Thunderbird has a full digital dash the tach display could be waaay off. For example at hot idle my Thunderbird idles right at 750rpm in park and 65rpm in drive with the parking brake on (both settings are within factory specs). Now those rpm readings are from a tach/dwell meter. The tach on the digital dash displays 5 bars at idle (800-1000rpm) when the actual rpm is about 250rpm lower. The factory buttstuffog tachs aren't much better. The tach in my Mark VII shows about 900rpm at hot idle. It's really at 700rpm according to a tach/dwell meter. The only way to know what rpm your Thunderbird's engine is actually idling at is to hook up a tach/dwell meter and find out. Once you've got a tach/dwell meter hooked up do a base idle reset: http://sbftech.com/index.php/topic,1031.0.html
Take a look at page two in the link. It describes the exact situation I'm talking about.

Thanks. I don't have a tach/dwell meter so I'm just going by what the idle was before I made the change. It was definitely out of range of the ECU to be able to bring it back down to anywhere near where it should be.

Fast idle after intake mod

Reply #84 – February 18, 2014, 08:38:36 PM

Quote from: TOM Renzo;429094

He already established that the bleed hole is LARGER!!! on the new TB. As far as the EGR holding vacuum that does nothing because if the diaphragm is blown the EGR wont open. And there is no VACUUM at the valve when the engine is at closed THROTTLE !!! The mounting gaskets and cooler adapter should be checked for corrosion and proper gaskets sealing correctly. He also posted that the throttle blade was in fact closing all the way.

I find it fascinating how installing an IAC UPSIDE DOWN would cause this as that is beyond comprehension as he totally blocked it off with a blank gasket!!!!! Just wondering how many IAC troubles you have addressed in your career STACKS. Better think over what you just posted!!!!!@

Stacks your post is fascinating because he clearly can not drop his idle with the IAC DISCONNECTED. HELLO if he could do this he would not be having a problem !!

QUESTION what would an upside down IAC motor DO as we sometimes mount them differently on different applications and also remotely. Guess you did not read my post on BLUEPRINTING THE IAC you should take the time and read it it is quite informative stacks!!

Here you go one of my IAC motors being broken down for blueprinting!!!

This is a really long thread with lots of turns and advice (for which I'm grateful), so I don't blame him for not following it all. And I'll outdo you all when it comes to dumb questions and dumber blunders -- like trying to measure vacuum on a heater core hose lol!

Fast idle after intake mod

Reply #85 – February 18, 2014, 08:48:38 PM

Quote from: TOM Renzo;429095

Normally i use the MIG to tack those holes closed. Once you close that hole off all your idle parameters will fall in to place. Those holes control the bypass air and there size is critical as you found out. A slight difference in diameter is very critical when it brings the idle circuit parameters out of speck. Remember once the IAC removes all the bypass air and the idle is to high the ECM and IAC are out of the equation. Some people use a steel rivet then tap out the center. But remember if it gets loose the part goes right in the engine. AND THAT IS NOT GOOD!!!

Hurray!! I'm good now!! The little copper pipe I stuck in the hole with the JB Weld seemed to be the perfect size and my idle is absolutely perfect -- even when hot. So either the hole was too big, or I still have a small vacuum leak somewhere that I'm compensating for with the diameter reduction.

So thank you everyone for the spectacular advice! I learned a ton just troubleshooting this problem. Now I can move and wreck something else -- like my exhaust :D

JCassity is promising me that I can fix my cruise control. So that will probably be my next thread if I can't find it here somewhere.

Fast idle after intake mod

Reply #86 – February 20, 2014, 08:54:40 AM

the cruise fix is in my diy link,, takes you to a thread on the topic by clicking the link.