2001 Vacuum related problem

Hi again guys,

Thanks for the info the other day. I haven't been able to do a lot of work but here's what has happened.

I started it cold for the first time in a while (not plugged in) and had some good noises. While trying to trace them down with a stethoscope I was greeted by my old friend - the puffing idle.

I figured while I was there I'd have a look. While warmed up and sitting at idle I have had a fluctuating idle of about 30-50 according to my scan tool. When the car is in gear with the foot on the brake it will pulsate and make you wonder if it is going to stall.

I can't give you a diagnosis and I can't seem to figure out what's happening but I can give you some data. While sitting there with the car idling and idle fluctuating, there periodically comes a puffing noise and another change in idle. After checking out I believe this puffing noise to be coming from the EGR vacuum regulator. It seems to be bleeding off some vacuum to atmosphere.

After checking with the vac guage, when the puffing is happening (sounds like the disc opening/closing rapidly) the manifold vac will drop about 1" or so and come back when that disc snaps shut - fast. Measuring the EGR vac and it doesn't change.

I can't reproduce it exactly but it happens when just sitting at idle. I can *sometimes* make it happen after a quick throttle snap on deceleration. Sometimes.

I can't figure why it is bleeding air to atmosphere and causing a further idle change. The manifold vac is only 19" and no change BEFORE it decides to bleed. It is the DPFE that controls the EVR via PCM but that tells it to open vac to EGR, not bleed to atmosphere.

The EGR has the required *little bit* of vac at idle but not enough to open it. The DPFE has the correct voltage according to specs. I can suty cycle the EVR with the scan tool. Everything seems to be normal but that vent to atmosphere with corresponding idle change shouldn't occur.

So is this normal? Is the EVR weak and periodically bleeding off air that it shouldn't be? Anyone have any insight into what this is?

Thanks guys...

Well my 2001 runs fine but I noticed it puffs or hisses when I rev the motor or snap the throttle.. Its been doing it for as long as i can remember,so mine was running fine so I never thought about passing the info along to the forum. I just assume its normal..Post back if you figure something out.

Hi Gary,

Good to hear from you again. This is a tough one to describe because of the terminology. I get another puff when I snap the throttle or turn the power steering too....or when it is cold. That one is vacuum and it is coming from the air breather which originates inside the open cavity of the drivers front fender. It seems to be amplified because of the bare metal cavity and it is noticed because of the proximity to the driver. That was just a poor design choice by Ford. Although I have a good book on acoustics here that has a section on building a tuned muffler. If I had a good flat response microphone I'd go record the sound and try and build a tuned muffler for it but I don't. I think a modest reference mic is about $300.

The puff sound in this case, and could be in your too, comes from behind the engine. The only thing I could seem to attribute it to is the EVR. Mainly because it sounds like a disc opening and closing. If it does it after a throttle snap it will do it say 5 seconds after it has returned to idle. And it may puff (open/close) 5 times over the next several seconds. The drivers side noise will suck really loudly as the throttle is being snapped open and not after deceleration. That one is normal but the EVR is very puzzling. It may be normal operation but that kind of fluctuation in idle and vacuum seems wrong.

I'll for sure post more info as I find out about it. If anyone else knows why that thing may be bleeding to atmosphere under no load please let me know.

AS for the loud drivers side puff that must be normal.. Thats were mine comes from... Not sure about the EVR...