Weird problem, any ideas? (idle, bucking, etc)

[TheClaw]

recently, I developed a small prob with White Devil.

The first symptom: the idle is weird sometimes..

Sometimes it'll idle perfect, but if I drive it a bit it'll then sometimes start idling weird.. It'll be normal, then kinda go up a few hundred, then drop down LOW to like 600, then back to normal, hold there for a while, then jump abit again.. It's not the normal idle surge, it's something else..

next, when driving, if I'm just barely pressing the gas while coasting, it'll buck a bit.. This is at right around 10-15 InHG on the boost gauge, and between 5-10% throttle input.. The bucking is kinda like the fuel is going on and off, and the car just kinda bucks. If I'm off the throttle, it'll coast smooth. If I'm on it more than the 5-10%, it'll speed up OK. Only thing is while coasting abd barely pressing the throttle.

There is something I thought of that could be coincidence - the BOV I have on there (stock) whistles under vaccuum a LOT more than the other one I had. And it happens to whistle right at about 13-15inHG.. Could that be it? Is the whistle noise the BOV sucking in un-metered air making it run crappy?

Idle speed controller dying? Or is that either dead or not, no in-between?? Anything else I should check?

Car is perfect other than that, can't figure it out.

Any help is appreciated! Spanks!

 

[romeen]

1) The idle issue sounds like idle surge to me, I don't know why you think it is not. Try this:
http://www.vfaq.com/mods/wayback/BradBauer/engine/surge.html

2) I recently had the same bucking thing going on that you are describing. It ended up being a boost leak in the vacuum line that from my boost controller to the WGA. I'm not sure why this would cause that but I fixed it and the problem went away.

3) Your BOV should not be whistling under vacuum.

Do a boost leak test. Leaks could be causing all of these problems. Fix the leaks then let us know if you still have problems.

 

[demografik]

Yup sounds like a boost leak to me. It's probably that leak whistling, not the BOV. Any whistling while boosting?

 

[TheClaw]

It's definitely the BOV that's whistling.. If I get under the hood, and play with the throttle, I can recreate it. It's definitely coming from the BOV.

I don't have any boost leaks, I'm guessing it's only leaking under a certain vaccum inhg (~15)

I'm going to get a new BOV tonight, I'll see if that fixes it.

 

[romeen]

"I don't have any boost leaks, I'm guessing it's only leaking under a certain vaccum inhg (~15)"

If you have a vacuum leak then that same spot is going to be a boost leak when the intake is pressurized/under boost. If it only starts leaking at 15 inHg of vacuum then it probably will start leaking at about 7.5 psi of boost.

 

[TheClaw]

What I'm saying is that the BOV is not leaking under pressure, it's leaking under vaccuum.

I hooked the system up to my compressor last week and it was holding 20psi for a long time.

The only SLIGHT leaks are at the injector seals, and it's BARELY leaking there.. The BOV doesn't whistle under pressure, but it does under vaccuum.

I'm just going to try a new BOV and see if that helps.. Other than that, I'm stumped.

Could the idle control motor cause these probs? It's only sometimes though, not all the time.

 

[TheClaw]

Changed out the BOV - still doing it. Though the idle seems better, it's still bucking at partial throttle when coasting.

damn.

 

[TheClaw]

I think I found the prob..

The flange that the BOV attches to - on the upper IC pipe - it's warped to hell.. If I tighten it down, I can see through to the other side under the BOV - the gap is that big..

I got some gasket maker and put a thick bead around it, hand tightened it, let it dry, then torqued it down. It doesn't leak anymore at all - in fact there's NO boost leaks at all now.. If that doesn't fix it, I'm stumped. I'm pretty sure though that's the prob. I'll need to have a new heavy duty flange welded on..

The gap was crazy wide.

 

[romeen]

Glad you found the leak. How does the car drive now?

 

[TheClaw]

Haven't driven it yet. Fixed it last night, but drove a beater to work since I'll be gone for the weekend and will need to leave my car in a parking lot.. I'll report back this weekend.