Not Sure How to Remedy This...

[Chris M 2]

Have had this issue ever since installing the K&N CAI back in March... asked about it back then but don't remember getting a definite answer...



Every time I start my ST after it has been parked for more than 3-4 hours (like every morning or after the workday), I get a BIG engine surge (like 2,200 RPM). I expect a bit of a surge at start-up, but this is way too high -- sounds like someone stomping the gas pedal.



It gradually eases down after about 3-4 seconds, but I'm concerned about the waste of fuel and unnecessary wear and tear on the engine.



Anyone have recommendations about how to deal with this? I remember hearing about that Slick 50 engine treatment stuff... does that work or is it snake oil?



I appreciate any advice anyone cares to offer (keep it clean!).

 

[Kevin Palmer]

You need to check for some sort of a air or vacuum leak I would think.



Once it gets running, it sounds like the IAC is doing it's job and controlling the idle even with the vacuum issue...

 

[Todd Z]

Chris,



Do you have a Xcal tune in the truck ???



Did you check the common elbow for a crack ??



Did you clean the IAC ??



DID you disconnect the battery when installing the intake...



I agree with coastie, There may be a slight vacuum leak.....



Todd Z

 

[Chris M 2]

No Xcal...



Checked the elbow a couple different times... all OK



IAC has been cleaned AND replaced (remember my weird stalling issue?)...



Yep, disco'd the battery when installing the intake...



OK, now how do I go about checking for a vacuum leak?

 

[Keola P]

My trac does something similar to yours but it doesn't rev that high. After starting in the morning or after work, it revs to about 1500rpm then drops to about 1000rpm after approximately 10-15 seconds. She's done it since I purchased her with 20,000 miles and no mods, and she still does it in the same manner after installing my k&n intake, throttle body, and xcal tune. No changes. So must be vacuum issue.

 

[Mike Dziubina]

but I'm concerned about the waste of fuel and unnecessary wear and tear on the engine

it's not a lot of fuel...don't sweat that part...my S/T does the same thing, but usually after i put the truck in park and then shut it off right away...now i let it sit for like 10 seconds before i kill it, hasn't revved up on start up since...as others have stated, probably IAC or vacuum issue

 

[Chris M 2]

Hmm... I'll have to try that, mike - CT -- thanks. By coincidence, I happen to let it run for about 30 seconds or so after I parked here at work today, as I was wrapped up in a radio program and wanted to hear the end of it. So I'll see what happens on start-up after work today.



I've cleaned and replaced the IAC with an OEM Ford IAC, so I know that's working as it should.



I'll probably look for a vacuum leak if the "let sit for 10 seconds" thing doesn't work for me.

 

[EddieS'04]

Chris, any time I made changes to my intake. When I hook the neg cable back I start it and let it Idle until it gets to normal temp. I dont touch the gas pedal till then. I cant say that made a difference. I just feel that it gave the ECU time to learn proper idle. Mine only revs at cold start to 1500 then drops to 1000 then to norm.

 

[Chris M 2]

mike - CT, I tried the "let sit for 10 seconds" thing you recommended. Didn't do anything for my ST.



I forgot to add something... it does the hard surge only after sitting for some time. For example, if I go to the store (or anywhere for that matter) and am parked for a few hours or less, it exhibits typical start-up behavior.

 

[Todd Z]

Try cleaning the MAF sensor....



Todd Z