High Idle after exhaust upgrade?

[Jstcruz]

After adding headers, flowmaster muffler, 2 1/4 inch pipe, taking one of the 2 inline cats off and cutting my airbox open, my truck Idles around 1100 rpm after I put it in park. It idles fine when its started and/or sitting in traffic. It started this right after I did the headers. Any ideas? Thanks in advance!

 

[Jstcruz]

Bump

 

[Jstcruz]

Any body? I'm thinking about changing out my coolant temp sensor. will this help?

 

[FIND]

No CELs? No vacuum problems? How much driving had you put on it since installing the headers? Has the idle changed over that time?

 

[shadowless127]

unhook the neg battery cable for like 2 minutes. It will reset your computer and it will relearn your fuel and air curves.

 

[Jstcruz]

No CELs? No vacuum problems? How much driving had you put on it since installing the headers? Has the idle changed over that time?

Check Engine Lights (?) None, no vac leaks that I know of and everything else has been maintained regularly. I have put a couple hundred miles on it with all this done and it hasnt changed much, but, I did try resetting the computer and it helped. But it does still idle high sometimes..

 

[Jstcruz]

I replaced the IAC, CTS and reset the battery after each reapair, STILL high idel! This is killing me, I just got a cel that will go out with a comp reset untill i have to jump on it to get into traffic. Would O2 sensors cause a high idel?

 

[FIND]

Not generally

 

[celly]

I dealt with a high idle for over a month. It was what everyone suspected.....vacuum leak. Plugged the leak. Truck idles beautifully.

There's a good chance you're dealing with that too. Vac leaks can be a pain to locate.

 

[Jstcruz]

Ok, finaly got the codes read on my truck. Low input to tps and lean reading from o2's. So, I cleanded every connection I could get to for the tps (it tested good) and replaced the upstream o2's. My idle came down to normal and the truck is running great! I drove it for about 30 miles and... The check engine light comes on...

 

[my98nnj]

Lean codes from O2's are telling you the engine is lacking fuel or getting to much air.
You wasted your $$ on new O2's, they were doing their job.

With that said, I would bet your high idle is indeed a vacuum leak.

 

[Jstcruz]

Lean codes from O2's are telling you the engine is lacking fuel or getting to much air.
You wasted your $$ on new O2's, they were doing their job.

With that said, I would bet your high idle is indeed a vacuum leak.

Im thinking its something to do with the iac (which is new) The idel was high again thismorning, when I unplug the iac it goes down to normal. It should barely want to run with that unplugged. Should I spend the money for a Ford IAC?

 

[Runnin'OnEmpty]

Sounds like the IAC is at least working, but the
uncontrolled curb idle is a bit high. It's adjusted
with a tamper resistant screw on the throttle body,
but dosen't normally require adjustment.

One thing that can cause a vacuum leak is the
PCV valve. It's frequently overlooked since it's
out of sight. The valve has a spring that holds it
open until manifold vacuum closes it upon startup.
If the valve is sticking from carbon build-up, it
will leak vacuum (when it shouldn't) and cause a
lean condition.

Another problem might be the vapor hose that runs
from the throttle body to the vapor recovery cannister.
If it's split or disconnected, it too will cause a vacuum
leak.

Just throwing some ideas out there, FWTW....

 

[Jstcruz]

Sounds like the IAC is at least working, but the
uncontrolled curb idle is a bit high. It's adjusted
with a tamper resistant screw on the throttle body,
but dosen't normally require adjustment.

One thing that can cause a vacuum leak is the
PCV valve. It's frequently overlooked since it's
out of sight. The valve has a spring that holds it
open until manifold vacuum closes it upon startup.
If the valve is sticking from carbon build-up, it
will leak vacuum (when it shouldn't) and cause a
lean condition.

Another problem might be the vapor hose that runs
from the throttle body to the vapor recovery cannister.
If it's split or disconnected, it too will cause a vacuum
leak.

Just throwing some ideas out there, FWTW....

The pcv was changed a while ago out of basic maintenance, but I will look into the vac line you mentioned. As of now its running fine but the way my luck has been - I'll be on here asking about something on the other end of the spectrum! Thanks for the input!

 

[Jstcruz]

This is still giving me issues. I am thinking about breaking down and taking the top end apart and replace all the gaskets and check all the lines real good. Any advice on a rebuild?

 

[delexploder]

With the truck running take a can of Carb spray with the little red straw and spray around anything that may be leaking if the idle changes then you have found it. Its an old trick.

 

[Jstcruz]

With the truck running take a can of Carb spray with the little red straw and spray around anything that may be leaking if the idle changes then you have found it. Its an old trick.

Thanks for that! I will do that once I get home.

 

[delexploder]

No prob. Just use some good strong stuff that flashes off (evaporates) fast like 2+2 gumsolve and go slow an methodical.

 

[delexploder]

How you making out? Keep us posted:scratch:

 

[©H®I$]

Hopefully its not your intake gasket. I had a shop replace that and it was quite the $$. But much less than what FORD would have charged me