legacycentral bbs

I'm pretty sure its a vac leak, and I'm pretty sure its the turbo outlet connection (The worm drive on the hose clamp is busted, I can spin the clamp around the hose with small effort) but I just want to double check.

1991 Legover Turbo, driving around town and at stop lights *sometimes* it idles funny, it drops down to like 500 rpm idle and wavers around, sputters sometimes. Other times sits at 730 or so rpm and fluctuates slighlty (can hear it and look at the tach, wavers very slightly).

Other times it idles fine. Like, starting it in the driveway. Idles fine. If I stall it because of the idle dropping low (and the grabby Exedy clutch), I start it up and it idles fine.

I *think* its boost related. After hitting some boost and coming to a stop, it idles odd. Any ideas?

Does your car have any leaks on the intake side of the turbo? I know mine has a ton of little ones that i need to seal with some silicone air getting in after the mass air sensor would cause it to idle funny. If the car is heated up, i would guess a little more air could slip in. Check the intake side just in case.

mine idled like shit, I sprayed silicone with the thing idleing around the intake manifold gaskets and it ran better. So I replaced them, its alot of work, specially cleaning the gunk from the old gaskets. Funny my no.1 intake gasket was blown and missing a large chunk, no idea how that couldof happened.

Mark,

mine is doing the same thing now. It will do fine sometimes, then other times it would jump around.
I thought it was the egr valve, so I cleaned up the carbon deposits and reinstalled, no difference.
Sprayed starting fuid on the intake where I thought holes were at, none there either.
I just dont get it, and am running out of ideas.

weird. mine does the same thing on my N/A... havent realli checked for vacuum leaks tho. except i did just install a cool air intake. all the connections are new and everything so i dunno either. it did that even before installing the intake.

anybody else have any ideas or insights?

Did you fix your leak yet?

I dont know, i mean the car runs fine, but the rpms still bob around.
I did the check on my egr valve (engine light came on) I had the car warmed up and idling and I pressed the egr up, the car stumbled like it was supposed to, so I know that is good. I cleaned up any carbon inside of it too.
But I still cant get right.
In park/nuetral, I can rev the car the bov whistels fine, but will come down and idle wierd, I have to hold my hand over the hole to prevent air from leaking out.
But when I go for a drive, it flutters still. It doesnt make any sense.

You said you know you have a boost leak because you don't have an operational hose clamp on the compressor outlet hose. How can you not know whether you fixed it or not?

Why did you decide not to run a recirculating blowoff valve setup?

I dont have a leak there or anywhere that I know off.
I didnt do a recirc setup because of the pcv system and the intake. I cant find an intake with enough nipples on it and with the right bend and such.

How can you not have a leak if you don't have a hose clamp?

I think you should recirculate. Take an intake without enough nipples on it, cut a 3/4" hole in it, and epoxy in a 3/4" hose barb. Then just use a stock-type BOV. That will eliminate that variable.

yeah I know, I am prob just gonna do that. I just didnt want to epoxy anything.

Why wouldnt I have a hose clamp there? I have clamps all over my engine bay.

Plus a new K&N filter, but nothing new.

You said right at the top of this thread that the hose clamp you had there was broken. That's what I was asking about when I asked if you fixed the leak.

If you don't want to epoxy maybe you could take the piece to a muffler shop and ask them to weld on a small piece of 3/4" OD pipe.

I am using a turbo intake right now, which is okay for now.
The broken hose clamp is DeusExMachina on the first post. I just had a similiar problem as he does, but no clamp of mine broken.

But why else would my egr be bad (engine light keep scoming on), and a recirc bov would fix all problems with idling and surge?

Agh, I'm sorry. I don't know what I was thinking. My mistake.

It was my understanding that generally once the computer throws an EGR trouble code, the EGR system shouldn't interfere with driveability.

hmm, well I took it off and did all the cleaning and testing and stuff, and reset the ecu.
If anything idle went worse until the engine light came back on.
But if my bov is tight tight, it will idle okay, but surge so bad. I am thinking of picking up a different bov or find a stock one.

If adjusting the BOV can make it idle right, then doesn't that mean the BOV is almost certainly the cause of your idling problem?

I think you should definitely find a stock-type BOV. Then you don't have to worry about trying to simultaneously close it at idle and not destroy your turbo.

yeah i know the bov is the cause of the idle, it cant stay closed at idle or open enough on boost. But why? I have tried both springs in, and even one spring in, but nothing. Myabe I just cant make sense of it.
The stock BOV how would that help, it isnt adjustable, but is it stiffer or just made better? And can that be run atmosph for now?

Why?

Why not?

What makes you believe that there's a spring setting that makes the valve stay closed at idle and also protect against compressor surge?

The reason a stock BOV would work is because it recirculates. It's supposed to be open at idle -- that actually reduces turbo lag. You can't run the stock valve atmospheric with good results.

yeah i know its supposed to be open at idle just a little bit. But any rev or gas, causes the bov to not close fast enough, and air just leaks out, even at low rpms, which is why my idle sucks.

The spring setting is supposed to be tight enough to stay semi-closed under idle and some boost, then be loose enough to open when full boost is met.

Are you mixing up the blowoff valve with the wastegate? The blowoff valve is supposed to be fully closed when you're making any meaningful boost. It's supposed to open when compressor outlet pressure is high but manifold pressure is low.

The stock BOV is fully open at idle.

yeah the stock bov is fully open, cuz it recircs.
But atmoshp bov arent, if it leaks air that the maf doesnt read, the idiling will stink.
So by closing it at idle will prevent that.
or am I just being hard headed again.

No, you're right -- if you want the MAF sensor reading to be correct, you do need an atmospheric blowoff valve to be closed at idle.

What I'm saying is that maybe any spring setting that's stiff enough to close the valve at idle will always result in some amount of compressor surge.

yeah I guess so, that is what I am beginning to conclude with. unless I was pushing a lot more boost or I had a different setup then maybe it would work.
I did read up on autospeeds site about their electronic bov, very interesting.
But I still say I rather spend my time now getting it to recirc and making that new intake.
So then I can have the bov as loose or tight as I want with no problems.