Evo Vacuum Leak? Options

[Kazz5]

Tired of it trying die when I lift the throttle - especially after a blip when not really moving ... who knows the vacuum system and can tell me where to check?

Thanks...

[turbohcar]

Try a boost leak check. That should automatically tell you where to look. I've got a boost leak tool, but mine is malfunctioning at the moment (can't get a stable reading). Vfaq should have instructions on how to make them.

[Kazz5]

Have one - only air I get is from BOV and MBC bleed-off ... gots to be something else somewhere the boost leak test doesn't catch. She acts like a vacuum leak with stalls ,etc.

[AWD DSM 1]

Boost leak check should catch most if not all of the vacuum lines since vacuum is typically created off the intake manifold. Might want to start checking some solinoids, ISC, etc... Are you running aftermarket cams? Idle speed might need adjusted.

I'm just brainstorming here...

[Kazz5]

Idle speed's good. Non-stock cams. ISC? Not getting any codes.

She idles fine - lopey, but good. A quick blip of the throttle when idling, however, can kill it. One of the funniest things is when I drop the hood the thing almost stalls, then recovers to idle ...

[ncgalant]

Are you running an aftermarket fuel pump? My old galant did that when I was overrunning the FPR.

[Kazz5]

Walbro HF 255 ... hrrrmmmmm... and how do I check that?

[turbohcar]

Yes, that is a possibility. I'm not totally sure if there is a way to check it other than buying an AFPR.

[natedogg]

Walbro HF 255 ... hrrrmmmmm... and how do I check that?

Fuel pressure guage. If its running higher than stock base fuel pressure at idle, you are overrunning the stock FPR. I don't know what the stock base fuel pressure is for Evo's. If its like the 2G's, its 43.5 psi with the vacuum hose connected to it.

[black92_tsi_awd]

Walbro HF 255 ... hrrrmmmmm... and how do I check that?

Is your fuel pump REALLY loud???

MY 190 is loud, from what I understand the 255 is a lot louder. Not exactly scientific but will gove you a hint.

[akamiami]

it might have to do with something al tuned on the car. as I've found, a low idle timing will promote a steadier idle on cammed cars, but have a pretty nasty throttle tip in advance when you're just easing into it out of an idle condition. this is exactly the type of thing my gsx is doing at the moment, though I'm not quite done playing with it yet.

bad news is that if I'm right, you'll need a reflash....

[Kazz5]

It's the thought of the reflash that's chappin' my hide. And yes, I can hear the fp. Also, I understand that 43's stock - if I remember right. Will do more homework when doing something with it becomes more imminent.

Let's play here. Yes, I'm dealin' with a flash. But how much of this flash is dependent on this aggressive pump pressure? If I knock it down to stock with an fpr will I risk the motor? It seems to me I can't do this w/o some good tools, like a wideband ... she's not running stock injectors anymore ... runnin' 650's so ...

I'll see if I can get Al's attention with a post on EvoM. I've already got a thread running there that started out asking about vacuum leaks just like this one ...

[Kazz5]

it might have to do with something al tuned on the car. as I've found, a low idle timing will promote a steadier idle on cammed cars, but have a pretty nasty throttle tip in advance when you're just easing into it out of an idle condition. this is exactly the type of thing my gsx is doing at the moment, though I'm not quite done playing with it yet.

bad news is that if I'm right, you'll need a reflash....

I'm working with what you're saying here, but you're talking about a stumble at slight throttle? I don't think I've got that. This is about lifting AFTER slight throttle.

Been at a stoplight and rev'd her slightly? This is much less than that... gentle application of the throttle is music, no stumble ...

[akamiami]

I'd just doubt this is related to an increased pressure problem from the FP. I've been running a 255 with no problems. The evo has a much more sophisticated control system for fuel pump voltage than a typical dsm so there are less problems with fuel overrrun at idle from the increased pressure as the evo actually sees less voltage at idle as I understand it.

[BudmannG]

This may not apply to you Kazz, But I was having the same problem with my 1g. I found that the problem was in my bov return line. Some how it was escaping to the atmospher and would cause the car to stumble like you explain. I would check that!

And as for your boost leak test, did you unhook the mbc so you could boost leak it to the 20-25 psi? How long does it hold pressure for?

I'm just trying to give you some ideas.

[Kazz5]

I've not done another boost leak test. Part of that is because I'm so convinced it's not a problem. God she pulls like mad. But I should - hopefully will soon. Been putting too much time into the new daily driver.

Anway, mentioned it to Al and he wants me to send off my ECU for a reflash for an "idle fix" ... ?

Two things go through my mind here:

One is I can always send the ECU to Works and see what it comes back like. I'm confident the driveability would be dialed in by them and not quite as confident that Al's flash would - just my gut feel. Of course, I also feel that Al's flash might do me better in the quarter and that'd be likely the first event this car's going to see of note this year.

What else goes through my mind is that there's some other problem. And therefore I'll bring another symptom into all of this. It's all seemingly related to my BOV(s). Yes, I have two. One is an APS which splits between atmosphere and recirc. Now, the stocker is full recirc but notoriously leaky and doesn't hold boost. Mine leaked at less than 10psi and therefore why I got the APS.

What made me try another - full recirc, btw - was because of the dying at throttle lift. I've been feathering the throttle when I lift in order to make sure she doesn't die (she doesn't all the time but shit, you don't want to deal with it ever so you prevent it as best you can - ya know?). So I went with the Forge product which Al's big on. It came preassembled with the instructions mentioning more parts than came in the box - bad sign. So I installed it. It's adjustable - spring tension adjustable (just like their MBC) by turning the dial. Now I've had it dialed out and dialed up (28 "clicks") as it should be for my peak boost. The problem is part-throttle driveability. God knows if I floor the thing she's balls-out going for it. But if I shift and hit the next gear at part throttle or if I take off in a gear at about 1/3 or half throttle she goes and then starts sputtering - the excess boost being redirected back to the intake. But she goes back, I assume, pretty hard because it can make the car buck. Surge, right? Bad news. I'm still dorking with adjusting it to see if I can get rid of the problem but it doesn't look good.

So, the reason I post this here - anyone have any idea that these 2 might be related? I thought they might be and that's why I tried to get a good full-recirc BOV which apparently was stupid. Works sells one and Twin Turbo's selling his used but I hate throwing bad money after bad money if it's not the root of one or both problems. At this point I'm very inclined to put the APS back on because it did drive a bit smoother ... oh, and adjust the idle screw to dial in a bit more dependability at throttle lift as has been implied in a thread or two I've reviewed.

Thoughts folks?

[natedogg]

If you are still using the stock MAF to meter air, you should try your damndest to make a fully recirc BOV work. Its what your ECU is calibrated for. All metered air should stay within the system until it passes through the engine and past the O2 sensor. I've heard good things about Tial's BOV. According to slowboy its one of the largest in the industry at 50mm so it shouldn't have any trouble bypassing all that pressurized air. This should eliminate any compressor surge that you are experiencing.

Now as far as curing your idle problems, I can't say the BOV will help unless its opening at idle because you have the set screw backed out too far. At this point, I think your idle problem could be due to either a bad ECU idle calibration or too much fuel pressure. I'm not ruling out too much fuel pressure because even at idle the ECU may still be expecting you to have a stock Evo pump which pumps much less than a Walbro 255. Even at a low voltage you may be getting too much fuel pressure at idle. I know Kris hasn't had any problems, but we've seen different DSM's respond differently to 255's in the past. My old fwd for example ran just fine on a 255 with no AFPR, but my AWD wouldn't idle for shit until I put an AFPR on and lowered the base fuel pressure.

[Kazz5]

Evo's FP is like 43.5 stock at idle and I understand w/the walbro most run about 50. Further, almost everyone that talks about it (EvoM) discounts that it's a problem on the Evo.

So let's say I get an FPR and do install it. Can it be installed in such a fashion that it's just a gauge so I can read her before adjusting it? I know it needs to be a 1:1 in order to increase the pressure as boost goes up. But I'd like to see where it's at and dial it back slowly to see if I can fix the problem. I'm assuming dialing it back is dangerous without a re-tune so I'd rather be REAL cautious.

Also, apparently HKS includes info w/their cams about bumping the idle screw and fuel maps for just such problems post-install.

My idle runs around 900 when good and warm and I'll likely try the bump.

As far as the BOV is concerned, I hear Works' is good as well - and I already have a relationship with them. Perhaps I'll call them up - I can even ask about both issues.

Keep the ideas coming - I'll keep posting updates.

Thanks all!

[natedogg]

If you put the AFPR on, there's no telling whether you'd still be running the same fuel pressure as you were on the stock FPR. B&M makes a fuel pressure guage with an adapter fitting so that you can place it on top of the fuel filter on DSM's. I don't know if this same guage and adapter would work on the Evo. I'd have to take a closer look at the fuel filter. They may even make a specific adapter/guage for the Evo.

I may have the adapter/guage combo that I used to use on my DSM before I upgraded the fuel lines. I'll see if I can find it and if it will work.

[turbohcar]

I just bought one of Full Throttle Speed's AFPRs.
It (along with most other AFPRs) has a gauge port right on it. Now, I know Full Throttle doesn't make an EVO AFPR but, had I not gone with the FTS unit I would have invested in an Aeromotive AFPR. They seem to be the best when it comes to fuel supply parts. Whatever you do, DON'T buy B&M's AFPR. You cannot lower the pressure with it (which is what you need to do) you can only go higher.

I know for a fact that the Aeromotive AFPR has a gauge port on it that you can plug an Autometer mini fuel pressure gauge into (DSM carries it) and be able to watch your fuel press. while you adjust it. The Aeromotive unit is a bit pricey especially when you add in the cost of the stainless lines you need but it is definitely of the utmost quality. www.slowboyracing.com carries the Aeromotive AFPR along with www.diamondstarmotorsports.com, which are two vendors that I would highly reccomend. I've dealt with both in the past and they are good businesses. Talk to Jon at Slowboy or Ryan at DSM.