Throttle body gasket leak?
 

Hey Everyone,

Just wanted to ask a quick question to those who would know if this situation is "normal" or not.

Bought my Ex with 68K miles on it. Has always had just a "slight" miss to it at idle. You can feel it in the steering wheel. I replaced IAC valve with Ford part, cleaned throttle body, checked all vacuum lines with carb cleaner, replaced all plugs and boots with Motorcraft parts. No leaks from exhaust manifolds (thank goodness... no broken bolts).

The one thing that bothers me is this: the intake manifold, under the throttle body, has this sort of "oil sweat" on it. Just under the throttle body... the rest of it is shiny clean silver manifold. Is this dirty kind of sweat I'm seeing evidence of the throttle body gasket leaking? Or is this substance on the intake manifold just normal gunk that collects under there?

I guess I should ask... is a slight shudder in the steering wheel while parked at idle just normal for the V10? Never owned an engine bigger than 350 cubic inches.. so these big engines are new to me.

Any experience or advice is very much appreciated!

James

I've had a leak on my throttle body through the gasket, you should noticeably be able to hear a hiss, and if you cannot, it is most likely not leaking bad enough to cause a problem at idle, or possibly not leaking at all. I assume the gasket was alright if you put it back on? The stain could be from many things i'd imagine, a drop of oil would do it, right? Maybe a spill.

I'm also learning as i go, only had a v10 for a year but do all my own work. You shouldn't feel any movement at idle through your steering wheel, as i don't on mine. Have you pulled codes to verify it was a miss at idle?

Thank you for the reply!

Unknown about the condition of the gasket as I didn't pull the throttle body off to clean it. I've never actually laid eyes on the gasket that is on it now.

There is a hiss sound coming from that area, not loud but you can hear it if you listen closely, hence why I have spent some time spraying carb cleaner around all the vacuum lines that plug into the throttle body. Problem is, when I spray the cleaner directly at the base of the throttle body, there is no noticeable change in idle speed. Then again, I'm used to a GM 5.3 ltr engine... what I am hearing may just be the way the intake sounds on these motors. :-huh

What I do know is that I can "feel" the slight shudder in the engine through the steering wheel when sitting at idle in the driveway.

I read somewhere a great article on why you should feel a slight variance in idle on all motors... had to do with timing inputs to the PCM and the miliseconds it takes for the PCM to react and make changes causes the balance in firing order to be off just enough to be able to feel the shudder every once in awhile. I don't know. Maybe I'm chasing ghosts.

I DO need to get a proper scan tool on it to check everything out and stop guessing. My ScanGauge II shows no codes returned, but I know it has its limitations.

Thank you again for your response. I guess I won't worry about the "sweaty oil-looking creep" that is happening on top of my intake manifold at this point.

James

You could definitely check the gasket to rule that one out, easy 15 minute job if you know what you're doing. Does the truck have an aftermarket intake like K&N etc.? Once those start to get a bit dusty and need a clean they will also start to whistle much like a vacuum leak.

I still have yet to agree that feeling anything through the steering wheel is okay, my v10 is at 205000 miles and i don't feel a thing at idle. Could be lucky.

For sure get your hands on a good code reader and find out whats going on.

Under normal operating circumstances, you should not hear any hissing at all for the v10 intake.

Your cheapy scanner should really have been able to pull up a miss on a cylinder... i want to lean towards a vacuum leak still

Thank you.
Didn't know if the Actron scanner I have would pull a miss fire code on these Fords. It read everything on my Suburban, but I don't know enough about the Fords to know if only certain codes can be pulled by the dealer tool or not.

I am leaning toward a small vacuum leak also since it only "shudders" about once every 20 seconds or so. I will keep looking... one question though...

If I am spraying carb cleaner or brake cleaner around the base of the throttle body or the nest of vacuum hoses and there is a small leak, will the idle change? Or is this a kind of "hit and miss" trouble shooting thing?

Thanks again!

James

Correct, it should smooth out your idle, but since you only feel a slight shudder every 20 seconds, and then its normal inbetween. It's hard to diagnose a vacuum leak by spraying around. If it was a bad vacuum leak 100% of the idle, and you sprayed into the leak, it should clear up and then go back to rough.

Best thing to do, is check.. check.. check.
Did you look at the throttle body gasket?
It is not at the base, it is behind the throttle, right after your air intake i believe... unless it changed in 2005

Thank you so much!

I will continue to check.
No, I have not physically removed the gasket and looked at it yet.

I thought that the gasket was under the throttle body where the four 10mm bolts held it down to the top of the intake manifold... :-huh

Trying to think of where there is another "joint" to put a gasket in...

I will look at it again and see if I can see what you are describing.

The V10 in my Ex is the same V10 from 2003...(I think that is the year they changed to a P.I. head) they didn't put the new 3 valve engines in the Ex, only the SuperDutys got them. I guess they knew they were ending the life of the Excursions that year so they didn't bother changing engines.

James

So your 2005 Ex is still Throttle by wire then right? you can see the cable come to the throttle body? If so, you take off the throttle plate and that is the gasket i have been talking about, and leaked on my 1999 F250

*The throttle plate is between the engine intake, and the air intake tube behind the filter. You should see the cable system on its side, can't miss it

Mine is still "throttle by cable". Will take a look tomorrow for the exact gasket location you are talking about.

By the way, I HAD "throttle by computer" on both our Tahoe and our Suburban... oh WOW I hated that setup! With factory programming, you get the "wait a second" throttle... and it allows the PCM to decide FOR you if you are taking off too fast and abusing the motor. I know I can't dodge it forever, but I will sure try to keep myself in vehicles that maintain a cable between my foot and the throttle plate for as many years as I can!

Thanks again!

James

Most likely your Actron scanner will pull most any code powertrain related on a Ford as it did your GM vehicles. My CP9580 found pending codes for misfire on cylinder #1 and another for "misfire first 200 RPM's" too---impressive!

Hope you find your leak without too much trouble!

Thanks! At least now I know my problem isn't a misfire at this point.

James

Good to know about the scanner, search for that leak then!
Let us know!

Will do!
Been raining here a lot lately so I'm waiting for the sun to return... nothing like getting some part of your vehicle torn halfway down and then the sky opens up on you. :'(

James

:) Any DIY outdoor mechanic that's NOT experienced the same thing just ain't doin' something right! :)

Once had to replace rocker arm pivots in a '77 Olds motor----the plastic tarp over the hood and fenders was great---only my back side and feet got wet! :D