EA82 Turbo causing stumble & miss ?

[quartus]

I've been having some severe stumbling at 3500 rpm & higher on my 86 GL-10 4x4 SW EA82T.

Here's the latest info, on the way home I tried to see how high rpms would go without missing while giving it little or no boost and it runs quite nice to 4300 rpm or so before I back off (for the whining) which leads me to think the ignition is okay. Its like it would run better without the turbo installed.

 

With that said, what is it about the turbo that would make it miss badly over 3500 rpm @ full boost (~5psi). I know there's a overboost fuel cutoff pressure switch (normally closed?) but that not suppose to engage till > 9psi, and since I have the fuel pump grounded at the pump I don't think it would cutoff the pump anyway ( http://www.ultimatesubaru.org/forum/...d.php?t=103540 ).

 

Things already done/replaced: Plugs, cap rotor, wires, timing @ 25btdc, fuel pump & filter, seafoamed through intake and rest in gas tank. Cleaned MAF & throttle body, no vacuum leaks, disty vacuum & mechanical advance good. Vacuum @ 22"Hg at idle & 5psi @ max boost.

 

Any more ideas Subaru Masters?

 

Prior info http://www.ultimatesubaru.org/forum/showthread.php?t=104058

Edited November 6, 2009 by quartus

[john in KY]

Don't think you have a fuel shutoff problem because I ran a turbo wagon at 12 pounds for years and never experienced a fuel cut.

 

Sounds like your turbo has a "whine". The only time the one on my wagon made a whine was pulling a steep grade, loaded and doing around 70mph. I wonder if your turbo could be spinning too fast for some reason.

 

Are you sure the turbo is boosting around 5 pounds? Just may be well above or well below. Not difficult to splice in a boost gauge and know for sure.

[quartus]

I have a boost/vacuum gauge installed and even verified the calibration of the gauge so the 5 psi boost is correct which is a little lower than the 7-9 psi FSM spec, I hope the boost will go up once I replace my leaky front pipe with the one I got from you The whine wasn't from the turbo, it was just a over-rev engine whine from waiting to long to shift, I was just trying to see how high I could get it without missing.

Edited November 6, 2009 by quartus

[joostvdw]

You can easily revs these engines to 7k, THEN you'll have an engine whine

 

It could still be ignition though, on boost the increase in pressure can "blow out" the spark, in other words, the spark is too weak. Spark plugs can also fail under boost/pressure. The chance of all four failing is very small though.

 

Hot wiring the fuel pump will not bypass the overboost protection (fuel-cut) since the ECU will just not open the injectors. This however is so severe it feels like you've just mashed your brake pedal making you head-butt the steering wheel

 

Does the stumble coincide with the passing of 0 PSIG? The fuel pressure regulator should switch "modes" so to speak when you pass 0, check if it's all properly connected and working. Easy check is disconnecting it and see if you'll notice anything Also the vacuum connection shouldn't smell like fuel (obviously).

[quartus]

Does the stumble coincide with the passing of 0 PSIG? The fuel pressure regulator should switch "modes" so to speak when you pass 0, check if it's all properly connected and working. Easy check is disconnecting it and see if you'll notice anything Also the vacuum connection shouldn't smell like fuel (obviously).

 

What do you mean disconnect? Is that to check the diaphram? It does feel like its starving for fuel, on the other hand I could see that it could be the spark is suppressed, my mileage is only ~ 20 mpg.