Low timing, high duty cycle, and no boost control!!!

[90 GSX]

To start this thread off, the car did not used to run like this. It seemed that out of nowhere it just lost all of its power. Ideally, I used to get between 16-19* of timing at 7000 rpm, with a duty cycle of no more than 75%. Now, I am getting between 8-10* of timing at 7000 rpm, with 1-4 counts of knock, my duty cycles are approaching and sometimes passing 100%, and I can't control my boost to less than 20 psi.

The part of the problem where I have lost boost control is very weird. I used to be able to hold the boost steady as low as 14 psi all the way to redline. The turbine housing is heavily ported and the exhaust setup uses a 2.5" pipe before the flex section of the downpipe. I'm running a big 16 with a joe p mbc and a stock, working actuator. The weird thing is, if I load the car up by flooring it at a fairly low rpm, like say 2500 in third gear, it will only spool to 12 psi and have low timing - low enough to count on two hands, so the car feels like a big rig. It is accelerating smoothly, but it's not picking up at all. Then once it reaches 4000 or 4500 rpm it shoots up to 20 psi like it finally was able to spool or something given that I'm seeing 10-12* of timing MAX. Is it becuase I'm not getting any timing that it's not spooling on the low end, or is it because I am dumping in too much gas that it can't stop the boost from rising. I mean what the hell is going on here? The car used to work, exactly in this configuration...

Once my boost shoots up to 20 psi, air is leaking through the PCV and the BOV so I'm thinking that it is obviously contributing to the high duty cycles but that doesn't explain why I'm not getting any timing in the first place. I also noticed that when the turbo spools hard on the high end past 20 or 21 psi I get pretty bad knock spikes up to about 15 counts so I let off before that. There is a reason that my duty cycle is so high under boost, and I believe that it is causing my car to pull out all the timing. My mas is reading from about 1800-2000 hz so that's in range. It's just my duty cycles are through the roof. And the even weirder part is, my logger says I'm running leaner than I should. I know that narrowband o2 readins can't be trusted but when you see 0.83-0.85 every time you floor it, and now you see 0.80 and 0.78 with much higher IDC's, there has to be a problem. I mean could I have a weak fuel pump? Whats the deal here.

Anybody...?

 

[Quasimondo]

Is the 8-10 degrees of timing with knock or without knock? Has this been occuring past one fill up (trying to eliminate the possibility of bad gas)? Have you made any recent changes to your setup, or did any underhood work that required a partial disassembly of your intake? If you have significant leaks through the PCV and BOV, those should be sealed up. You should also perform a boost leak test to make sure there are no other leaks that you don't know about. Those leaks will contribute to a high duty cycle.

How is your boost controller hooked up? Are you getting your boost source tee'd off from somewhere other than the nipple on the compressor outlet? If you bypass your MBC and you can less than 20 psi like before, then you have to look at whether there's a problem with the MBC or with how it's set up.

As for your fuel problems, higher duty cycles and lower O2 values would lead me to believe that there's an issue either with the fuel pump (though I've never heard of any Walbro pumps going bad) or the regulator. When was the last time you replaced your fuel filter? You can also pull the fuel pump and make sure there is nothing clogging up that sock, preventing the pump from drawing up fuel. As a last measure, check your fuel pressure regulator to make sure it's not leaking and preventing a true 1:1 increase in fuel pressure. This is a problem more common with the bolt-on fuel pressure regulators that Full-Throttle Performance used to sell. An easy fix is to wrap the adjustment screw with pipe sealing tape available from the plumbing department of any home improvement/hardware store.

Hopefully somebody else will chime in, but let us know what you find.

 

[90 GSX]

Is the 8-10 degrees of timing with knock or without knock? Has this been occuring past one fill up (trying to eliminate the possibility of bad gas)? Have you made any recent changes to your setup, or did any underhood work that required a partial disassembly of your intake? If you have significant leaks through the PCV and BOV, those should be sealed up. You should also perform a boost leak test to make sure there are no other leaks that you don't know about. Those leaks will contribute to a high duty cycle.

How is your boost controller hooked up? Are you getting your boost source tee'd off from somewhere other than the nipple on the compressor outlet? If you bypass your MBC and you can less than 20 psi like before, then you have to look at whether there's a problem with the MBC or with how it's set up.

As for your fuel problems, higher duty cycles and lower O2 values would lead me to believe that there's an issue either with the fuel pump (though I've never heard of any Walbro pumps going bad) or the regulator. When was the last time you replaced your fuel filter? You can also pull the fuel pump and make sure there is nothing clogging up that sock, preventing the pump from drawing up fuel. As a last measure, check your fuel pressure regulator to make sure it's not leaking and preventing a true 1:1 increase in fuel pressure. This is a problem more common with the bolt-on fuel pressure regulators that Full-Throttle Performance used to sell. An easy fix is to wrap the adjustment screw with pipe sealing tape available from the plumbing department of any home improvement/hardware store.

Hopefully somebody else will chime in, but let us know what you find.

The 8-10* is without knock, but as I approach the high end the turbo starts spinning out of control, I will see knock with the same or slightly more timing because it's on the high rpm range. I think 13 is the most I've seen, when in reality I'm chipped to be running 19* at 7000 rpm with optimal conditions. I can audibly notice a difference in the way the turbo sounds, it gets really high pitch like its really movin fast, and I usually get knock around there.

It has occured over multiple gas tanks.

I have thoroughly checked for boost leaks. I jiggled everything around, stuck my ear really close to things, and I did end up finding some really small leaks and I fixed all of them but it didn't make a significant difference. The car is smoother but it still has no power. I have no boost leaks any more at 20 psi on my boost gauge during a leak test.

My compressor outlet no longer has a nipple on it so the mbc is T'd into my BOV line. It has worked very well in the past before this problem arose. I'm also positive that it is hooked up correctly. I even took it apart the other day to look for obvious damage... but it was just 2 balls and a spring. How can I bypass the mbc? Just seal off the vacuum lines and let the actuator spring control the boost? I think that's a really good idea I haven't tried yet...

As for the fuel... I wish I had a way to see my pressure while the car is boosting. The only gauge is right on the regulator which is an aeromotive. I pieced together the entire kit myself. The feed, return, and the lines from the rail to the regulator are all -6an braided and the the fuel filter is a brand new mitsubishi unit with the banjo bolt replaced with a 12mmx1.25 -6an fitting. The fuel system was working extremely well because at 18 psi on my big 16g my duty cycle was barely hitting 70% with a 190 fuel pump and 550's at 43 psi.

The adjuster screw and the air nipple on the regulator leaked but I sealed those when I did my "major boost leak test" and sealed up all the slow leaks. I have no way of testing the regulator under load unless I could get a gauge that screwed in that I could somehow stick out of the hood or something.

I'm going to take it for a spin and disconnect the mbc right now.

 

[BISHILVR]

If you still have a cat converter it might be time to look at it for partial clogs etc.

 

[90 GSX]

I compared the new logs to the old logs I took when the car ran half decent. It looks like the timing and duty cycles are as far off as I originally thought. Around 3000 rpm I am supposed to have 10-12 degrees of timing and it should rise to 19 by redline (which it did in the old logs) but now I'm topping out at 13 or 14 with knock whereas I never had that problem before. So I think I can safely say that the loss of timing I have now on the top end is due to knock retard, but keep in mind I didn't have knock before.

I notice also that my turbo doesn't hold boost. It spools slowly on the low end, it feels like it struggling to maintain 11 or 12 psi, the boost gauge flutters like it's really trying. Then once I hit the high end around 4500 or 5000 the boost shoots up like a rocket but I still have knock and no timing and the car just has no power.

I ran the car off the actuator with the mbc disconnected and now I am able to stop the boost from rising at about 17 or 18 max instead of 20 or 21+. The boost control problem is still there, it's just less pronounced. First it will hold 13 or 14 psi albeit kindy of shaky until about 4500 or 5000 rpm then it shoots up to about 17 or 18 quickly. The problem is, I can actually see the point when the wastegate can no longer hold the actuator spring pressure. It's not really a slow creep, it creeps 4 or 5 psi in a couple seconds. The car never did this before. I used to be able to hold 14 psi until redline.

The car is also doing something else which is VERY strange. Occasionally as I drive, and this only happens rarely, the car feels like it lost 2 cylinders. In a split second I can go from normal acceleration to chugging along really hard then I feel the power slowly and smoothly come back in. It's very weird... it happens at idle too, my vacuum will go from 18 or 19 in Hg to about 10 inches. I caught this weird occurance on my logger the other day and the only odd thing I noticed was that my o2 trim and o2 voltage were fully lean. I'm pretty sure it's a fueling problem because the car still drove and the turbo spooled at a flick of my foot, MUCH faster than usual... I'm assuming it spooled so fast because it was extremely lean. I didn't floor it or anything, just gave it some gas a couple times to analyze the problem while it was happening. Could it be a resistor pack? Pump solenoid? Rewire relay? Bad pump? Is it even fuel???

I

 

[BISHILVR]

Weird, it almost sounds like you have some type of valve sealing problem or gasket problems.

 

[Quasimondo]

The problem might be with the actuator itself, perhaps. I'm wondering if the diaphragm in it is starting to fail. Can you get a replacement actuator to swap out?