f150 surging idle

[tarheel53]

Hello all, here is a little background: 2004 f150, 500 hrs - slowly developed a hesitation/stumble that occurred when advancing throttle from idle - also had lost top end power and would not hold steady RPM above 3700.

After replacing : the VST filter, inline filter above VST, water/fuel separation filter, front bowl mounted filter, plugs ..... and having injectors professionally cleaned, the stumble/hesitation is gone and top end power is back. BUT - I now have a new problem :

When I first started the engine after completing the filter/injector work, I noticed that the idle was 'hunting' between 600 - 900 rpm with a little cough or stumble at the low rpm each time. Anyway - I took the boat out for a power run and the engine ran great. Back at the dock, the 'hunting' idle was unchanged after running for 20 minutes a varied RPM. Turned engine off and then re-started it ( twice) to find that the idle is now holding steady at 1100 rpm

Any ideas on where to start or what to look for ? Thanks in advance for any advice or assistance you fellows could offer. JB

[TownsendsFJR1300]

With the cowl off, run the engine (docked, in the water), then turn it off.

Can you hear a clicking coming from the top, starboard side of the engine?

The Idle control valve is there and controls the idle. When you TURN OFF the engine it re-sets and CLICKS maybe 2-3 seconds...

If its getting over 200'F, that's also a clue its failed.

[tarheel53]

Thank you for the advice - don't think I can get to he boat until Sunday, but will run it and listen as suggested . I was very careful reassembling intake , hoses etc after the VST filter change ,,,,, but if something is amiss and I have a small air leak - could that cause the idle problem ?

[tarheel53]

Oh - and the 200 degrees refers to the actual idle control valve itself ?

[TownsendsFJR1300]

Thank you for the advice - don't think I can get to he boat until Sunday, but will run it and listen as suggested . I was very careful reassembling intake , hoses etc after the VST filter change ,,,,, but if something is amiss and I have a small air leak - could that cause the idle problem ?

Any vacuum leak can cause idling/running issues.

However, IME, if you had a vacuum leak, the idle wouldn't be hunting, it'd be crappy, or higher (leaning out). At the end of your first post, I missed its staying at 1100 vs 750. It might be worth your while to re-check the rubber gaskets especially between the intake manifold and head. It wouldn't be hard to have one move/drop during installation.

Re the temp of the ISC, yes, 200F of the unit itself would indicate its failed / failing. The clicking is VERY obvious and if you pay attention, you can hear it with the cowl on (easier with it off).. If it idled good before, I kinda doubt the ISC is the issue.


seals #15 and #19 specifically:

http://www.boats.net/parts/search/Ya...202/parts.html

[tarheel53]

Townsend ..... OK, thanks ...... the throttle bodies never came off the intake, so I will pull it back apart and check the # 15 seals.

If the ISC is clicking as you describe, does that indicate it is functioning correctly ?

Recap : idle has always been perfect on this motor ...... only issues were a stumble when applying throttle from idle and loss of higher rpm power. This idle speed problem only showed up after the VST and injector service.

[TownsendsFJR1300]

Townsend ..... OK, thanks ...... the throttle bodies never came off the intake, so I will pull it back apart and check the # 15 seals.

If the ISC is clicking as you describe, does that indicate it is functioning correctly ?

Recap : idle has always been perfect on this motor ...... only issues were a stumble when applying throttle from idle and loss of higher rpm power. This idle speed problem only showed up after the VST and injector service.

If you didn't pull an assembly(and the o-rings), disregard checking them.

And yes, when you turn the engine from running to OFF, it CLICKS as it re-sets for the next start up (normal and expected).

It sounds like a vacuum leak somewhere, perhaps a cracked hose, not fully on, o-ring seal moved, etc..

Good luck and please post back what you find..

[rodbolt17]

or
someone failed to plug in a sensor.
typically if any sensor is left unplugged idle timing is fixed and it idles about 1100.

or someone dinked with the linkage.

[tarheel53]

Well the 'someone' would be ME !! I'll look carefully at all hose connections and sensor plugs - this was my first effort with the VST - so entirely possible I missed something during reassembly. I don't think I dislodged any of the O rings where intake mates to the block, but if nothing else is revealed, will check those. Don't think the throttle linkage was 'boogered' - I carefully removed the plastic 'rod end' that connects the linkage to the throttle body and re-attached but nothing was turned or adjusted. Thanks for all the help !

Think my next 'project' is the balancer ........ I didn't even know it existed ( much less the problems with them ) but after reading here and listening to mine with cowl off ......... it definitely issues a noticeable whine.

[tarheel53]

Problem solved - idle air sensor was unplugged - ' some ' knucklehead failed to plug it after the VST fiter change.

Thanks to those who weighed in - sorry for waste of time !

[TownsendsFJR1300]

Thanks for the update, glad you found it!!

Kudo's to Rodbolt for nailing it..



Now the balancer. Don't put that off if its noisy, that will destroy your engine should it come apart...

The flywheel can stay on. Mine was done under warranty and I watched as the mechanic did it while the boat was in the water. Maybe a half hour as he knew the short cuts..

[tarheel53]

Yep - balancer is next - I'm looking through the manual you sent to figure out the steps. Planning to order it today from the site.

Thanks Scott

[rodbolt17]

go to the dealer.
get a copy of the tech bulliten.

[tarheel53]

Will do - thanks !

[boscoe99]

F150 Balancer Replacement Instructions