Wheeze??

Chris McDowell

Registered User
Ok, new to the supercharger arena as of March of this year. I have a '90 SC/5spd. I have already had to replace the idle air bypass valve, but now have an issue (2 months after the valve) where when I shut the car off, or lift off the gas the (supposedly) intake track is producing a fog horn like sound. It is most prominent when shutting the car off, but I can hear it while driving also. No warning lights for this, and all gauges are normal, as is the cars operational abilities. Help? I would assume that we are looking for a sensor or solenoid, but this is a new toy to play with and I have not yet purchased a set of books on her.

Thanks to any help.
 
Ran into a similar type concern on a 5 liter that had had its valve covers changed to an aftermarket type. Drove me nuts trying to figure it out for about three days. It was most noticeable when you shut the car off. You would hear a loud groaning noise that slowly died away, like pressure bleeding off. Sometimes you could hear it while the engine was running, especially after a deceleration. It sounded like it was coming from the crank damper area so we threw a used damper at it just to see if it would change. It didn't.

Anyway to make a long story short it was the PCV system. When the valve covers were changed the new covers didn't have any provision for fresh air entry so the PCV valve would pull a vacuum on the crankcase. After a while the vacuum was deep enough to overcome the crank damper seal and the seal would vibrate as air passed by it causing the groan. Added a vented oil cap and the concern went away.

A quick check would be to just remove your oil filler cap. If the problem goes away you know the vent for the PCV system is blocked.

A/C systems will sometimes make high pitched squealing noises as the pressures equalize. Usually means a restricted orifice/expansion valve in my experience.
 
wheeze?

I will have to check the motor while pulling the oil cap. That makes sense. As for the IAC.....I just replaced it a couple of months ago, I found four of them in a u-pick-it wrecking yard for a total of $5.00 for all of them. Maybe it is starting to go away, but the main notice of the IAC was that my idle jumped from 850 to an un-negotiable 2500. That was fun with a 5 spd. haha Thanks for the info.
 
Yeah I understand what youre saying but it could be starting to go. Mine did that fog horn sound for about 2 weeks then one morning Bam 2500 RPM idle. That fog horn sound usualy comes from air getting by through a small rip in the acordian diaphram inside the IAC. Once the rip gets big enough you loose the fog horn but gain a high idle RPM.
I've been on a few other Ford sites and it a pretty common problem, it goes by different names such as fog horn,moosing,goose call.
In the end they all come down to the same thing, bad IAC.
 
Moose Call

Appreciate the info. I did the check with the oil cap to find no change. I will dig through my left over IAC's. and change it out again. Thanks heavens for u-pick-it wrecking yards. I pulled either four or five IAC's the last time, so as easy as it is to change I think I will skip the new one. One of these should be good, right. haha.
 
Well to be honest most of the ones you will find in boneyards are old and age is what kills the plastic diaphram. The diaphram gets brittle with age and cracks. The part # for a new on is E9SZ-9F715-E if you decide to go with a new one. You can get it for about $65.00 from Ford and then you wont have to worry about it for several years.
 
On my drag racer I've started getting a high pitched whining whistle about 2 seconds after I shut it off and was planning on replacing the EGR valve since it vibrates. My IAC is fairly new. It also makes a similar noise after it's been running a few seconds almost like a squeaky bearing on an idler pulley. It sounds like it is coming from the back of the engine and can be heard just about as loud inside the car as outside. The O 2 sensors have gone bad, too. If they're leaking they could account for some of the noise. I'll replace all of this today and see how it sounds. It's not affecting the performance any as I ran 13.1's last weekend.
 
Hey Mike..i actually have the same squeaking problem right now, like an ungreased pulley or something coming right around the bypass valve butterfly. One you initially turn the car off and the butterfly shuts, it quits just then. So im pretty convinced it has something to do with taht butterfly, i just dont know what. I just wanted to ask if you fixed yours, and if so..how? Thanx buddy
 
That's been awhile. I had a vacuum line misrouted accidently and it was making pressure inside the valve cover on that side. With the throttle plate open it bled off the pressure instantly but with it closed and sealed the pressure escaped through some tiny leak and whistled. I rerouted the hose to where it was supposed to be and it went away.
 
Hey Mike..Im trying to find out where exactly it is that the vaccuum lind for the bypass vavle routes to. does it go on the intake plenum (the one with the throttle body attatched)? or does it go to the inlet plenum? Im thinking maybe we had the same problem and possible i have it routed wrong. When you get a chance please let me know..thanks
 
The hose/tube from the driver's side valve cover routes under the blower snout and over to the air inlet tube in front of the throttle body. It's a fresh air intake and not a vacuum line. That's the one I misrouted.
 
unwrapped the squeeky problem

Well i found the problem. the my driverside valve cover is different from my passenger side valve cover and that bank actually pulls a vacuum, so im just going to put a fresh air oil filler in its place and let it ride. that valve cover is from a early model, like 89-90 super copue on my 95 and the pcv system is different, so im going to do that. If you see any problems with this idea, please let me know, but i dont see any problem with putting an oil filler cap in there.
 
You know, they make those little bity air filters that look like a miniature one. They're about 3" or so in diameter. If that's what you mean, they work. A lot of guys use those.
 
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