91 SS surges under boost and stumbles off-idle. Still broke

[Boostedballs]

OK, I have jacked into a few other threads with similar issues but nothing quite like this, so I decided to make a new topic.

Issue:
-Under heavy engine load, I feel a soft jerking / loss of power. This is usually worse when the engine is fairly cold. (this tells me I have a leaning issue). Sometimes the engine pulls hard like a raped ape with no issue.
-The boost gauge likes to sit around 9-11psi but sometimes it sits at 5psi, even if I've been WOT for a few seconds. The power doesn't correspond to the boost level. Sometimes it pulls hard at only 5 psi and is weak at 10psi. Boost comes on really quick either way, whether it's making good power at the time or not. This tells me the Cats aren't clogged?
-The turbo noise is louder than any stock turbo car I've owned. It sounds like the BOV is letting air pass through it (sometimes). Like a hissing, rather than a whistling. ???

The other issues may or may not be related:
-very slight hesitation when I just barely crack open the throttle. I didn't notice this until recently because I usually don't go easy on the trottle. (if I hit the gas any faster, it will take off without the hesitation. This sounds like EGR problems to me.
-crankshaft pully has a slight wobble.
-knock sensor was replaced by previous owner. don't know why...

so far I've:
-replaced fuel filter, plugs, wires, air filter.
-test drove with knock sensor disconnected, also tested with O2 sensor disconnected. It runs the same, except for the O2 throws a CEL after driving for an hour or so.
-checked WG plubing and solenoid operation, and checked intake for vacuum leaks with starting fluid.

I'm thinking I have an issue with the:
fuel pump, EGR valve, crank timing gear key, BOV, or knock sensor wiring.

racing season is here, I need this car to perform!

I have a Walboro 255 in the mail (if the newbie Ebayer actually sent it) and I have a bunch of go-fast goodies to put on this thing, but I want it to run right before I go and kill something inside the engine.

please help!!!

[Radial GT1]

I have the same issues. Let me know if something works for you! Thanks

[vrg3]

You didn't get a knock sensor code when you drove without the knock sensor?

Your problems point to a problem either with knock sensing or with actual knock.

Advice to all 1st-gen Legacy owners is that if your knock sensor is still stock, replace it. The original design is flawed and it may be malfunctioning even if the ECU doesn't think so. That's probably why the previous owner did that. You may want to double-check that the connector on the sensor is white, indicating it's the new design.

It is possible your engine is running lean, yes. Putting the Walbro pump in is probably a good idea.

What kind of plugs did you put in? Many board members have experienced problems with Bosch plugs. NGK BKR6E-11 plugs are the usual recommendation.

Your car has no EGR system.

Can you run my scantool? Maybe we could find out what the ECU's doing with knock correction.

11 psi is overboosting. Is it possible that the restrictor is missing in the boost bleed line?

[Boostedballs]

Thanks for the response.
I did not get a cel with the knock sensor disconnected. I only drove it a mile or so. I think the connector is white, I remember it being a light color.
I used the NGK BKR6E plugs. I don't remember it having a -11 at the end though. I gapped to .028. The old ones were worn to about .050. I thought that was the smoking gun, but no, that would be too easy.

I also forgot to mention that it has a faint knock sound when the engine is warming up. It is a single hit every 15 seconds or so. Very metalic and I never hear it while I'm driving the car. I've experienced rod knock in a few engines and this doesn't sound to me like rod knock.

There is a small plastic connector inline from the compressor to the top of the solenoid, I assume is the restrictor. My boost gauge is an autometer ultralite.

I'll have to research your scantool, since I know nothing about it.

no EGR? I guess it's obvious I have been messing with the EA series engines for too long.

Oh, I raced my wife last night in her stock 1997 Legacy GT 2.5 and I beat her by a car length or so. This is while my engine is bucking under boost and I didn't punch it until I seen her punch it so I started out a car length behind her! It was fun, stupid to hotrod this thing the way it is, but still fun!

[vrg3]

The knock sensor code should come up right away, I think, if the sensor's missing. That makes me thing that something's funky with your knock sensor wiring and that that's likely the cause of the problems.

.028" is a rather narrow gap -- the specified gap is 0.043", or 1.1 mm (which is what the -11 means in the part number). The minimum specified gap is 1.0 mm, or 0.039". Maybe try gapping them according to the specs?

Interesting about the knocking sound... I can't think of something that would happen about every 15 seconds or so.

That plastic piece is not the restrictor I'm talking about. Look at the vacuum diagram -- the hose coming off the bottom of the solenoid is supposed to have a restrictor inside it.

A lot of our cars suffer from MFS -- Millenium Falcon Syndrome. "It's the fastest hunk of junk in the galaxy."

[Boostedballs]

Yeah, I put my gap that tight just to see if this was a weak ignition system issue since the higher the cylinder pressure goes, the more power is required to light off the plug. I thought it was a good test to check the coils out. The new plugs seemed to have zero effect on performance.

I guess I'll be doing the coffee cup mod this weekend and I'll take a closer look at the WG lines. They looked stock to me. I take it I would have to remove the line and look inside of it? I cant try to squeeze it to see if it's there? hmmm

[vrg3]

Well, the stock restrictor is a brass piece about 1mm in length, so you should be able to feel it in the hose.

[Boostedballs]

well, the wastegate has the restricter orifice in the right spot. so I'm looking at fuel pressure or knock sensor wiring as the root cause.

***I just installed a used walbro 255 from ebay and the pump is toast! Makes so much noise, I can hear it in my house with the car idling in the driveway! The engine pops when I try to give it gas. Good thing the seller already left me feedback.

I guess the car will be down for a few days until I can find another Walbro gss342. So, I'll install my 3" downpipe while I wait.

[vrg3]

Walbro pumps do tend to be quite loud even when they're working properly.

[Boostedballs]

ok, I just installed a brand new Walbro gss342. It is pretty much silent, especially compared to the used one I tried from ebay.

BUT- the "surging under boost" issue remains. It's sorta good news in that it may mean that the engine hasn't been subject to leaning under boost.

but this also means that I have to continue working on this! DANG!

so, what is left???
- knock sensor wiring?
- crank gear key?
- timing belt off a tooth?
- clogged cat?
- bad BOV?

-case of beer to someone that can scan this while I drive it...portland, OR

[vrg3]

Yup, all those things could be involved. I forget -- have you checked out your knock sensor and made sure it's the updated design? Do you know how old the sensor is?

[Boostedballs]

the recipts that came with the car showed that the knock sensor was changed about a year ago. It is the newer one with the white connector.

[Boostedballs]

I hooked up an LED to the wastegate actuator so I can see from the cockpit when the solenoid is energized. It turns out that the solenoid is powered at some really odd times. It doesn't even come on until I have been driving for a few minutes. Then, It comes on and stays on for a while, doesn't seem to matter what the car is doing at the time. The engine seems to make more power when it is energized but not always. Very strange. The light doesn't seem to correspond to the surging under boost. Time for a boost controller anyway.

Then I installed a 3" stainless downpipe. I had to shorten it a couple inches and clearance it for the auto trans pan. It's fine, because I just cut the O2 senor section out and TIG welded it back together. The engine is much more responsive now, but the "on off n off" business is still present under boost. There is still one CAT left in the system and I really couldn't see if it was clogged or not.

I guess I'm gunna build that scan tool.

[vrg3]

Your LED approach may not be showing all the information. The solenoid is not simply energized or not energized; it is driven with a varying duty cycle.

If the ECU is not driving it right, I wouldn't just replace it with an aftermarket boost controller. The ECU thinks something is wrong. If it's correct, you should fix what's wrong. If it's incorrect, you should fix the misperception so that the ECU doesn't do dumb things with your spark timing.

[Boostedballs]

Yeah, I just installed an LED to show me a little bit about what is going on. I know it has a pulse, that's why I went with and LED versus a regular bulbe. I can see that sucking flashing sometimes slow, sometimes really fast, never solid though. What gets me is why in the world it is flashing while i'm at cruise with the intake under vacuum. Sometimes, with the same engine load, the light doesn't flash, then does, then doesn't. there's no rhyme or reason with it as far as I can tell.

I'll bet the problem lies with the knock sensor wiring.

I have two laptops and neither have the connection I need for the scantool. Are there other scantools out there that are affordable that will do the same thing?

[vrg3]

Neither one has a parallel or a serial port?

I don't know of any affordable options if you don't have either of those ports.

[Boostedballs]

Neither one has a parallel or a serial port?

I don't know of any affordable options if you don't have either of those ports.

nope, just USB, firewire, etc. I have my eye on a couple old laptops on craigslist for cheap...

[Boostedballs]

also, the issue is VERY much worse when the engine has only been going for 10 minutes or less. When I have been driving for a while the car has much more power and the issue is less obvious. This makes me think that I don't have a real detonation issue because usually detonation is worse when an engine is hot. I'm going to install my water/alky injection anyway and if it makes a real difference, then maybe it really is a detonation issue.

I'll hold off on the nitrous kit until I finger out the root cause of this issue first.

[SubaruNation]

also, the issue is VERY much worse when the engine has only been going for 10 minutes or less. When I have been driving for a while the car has much more power and the issue is less obvious. This makes me think that I don't have a real detonation issue because usually detonation is worse when an engine is hot. I'm going to install my water/alky injection anyway and if it makes a real difference, then maybe it really is a detonation issue.

I'll hold off on the nitrous kit until I finger out the root cause of this issue first.

you're going to NO2 a turbo car...

[Boostedballs]

NO2 is gooood.

I'm setting up a reverse 2 stage system: 40hp and 30hp wet shots initially, then the 40hp shuts off at 8-10 psi and the 30hp shot stays on until I cross the line.

That should take care of the lag and the slugishness of the 4eat trans and provide a little something for the top of the track too.


Further down the road, when I get some good internals and the 5 speed swap, I'll up the jets a bit.

[Boostedballs]

ok, I picked up a Compaq Armada 4120 hotrod laptop today for the ultra low Craigslist price of $20. (with extra batter and nice case!)

I'll be trying the scan tool in the next couple days. Hopefully I can get it to work so I can monitor my timing and boost control.

Super stoked!

[Radial GT1]

I had a stumble problem off idle to on the gas lightly, it was a failing TPS. I picked up a whole throttle body from blackbart and it fixxed that problem.

I am also still trying to fix my problem that is almost just like yours.

[Boostedballs]

I had a stumble problem off idle to on the gas lightly, it was a failing TPS. I picked up a whole throttle body from blackbart and it fixxed that problem.

I am also still trying to fix my problem that is almost just like yours.

And you replaced your MAP sensor right? That is like $300 from the dealer. No way I'm paying that. I'll adapt something before that!

[Boostedballs]

Well, I tried to get the version 6 scan tool to work but it hung up on the start. Version 5 did the same thing. I'll have to figure out what to do with my parallel port config or something...network guru I am not

[BXSS]

Nitrous can wake the dead.

Make sure all your issues are resolved before you spray the car.