My 86 GL-10 Wgn has a noticable miss/stumble @ ~3500rpm. New cap/rotor/plugs/wires installed. Any ideas? Also when I bought the rotor I was given the wrong one (with the set screw) or so I thought. It turned out that the rotor that fit (push on) was listed for a nonturbo , what would be the effect of a nonturbo distributor in a turbo engine?

different vacuum advance.. which *could cause the problem you are having.

I also noted that the replaced rotor seems "short" ie the spark has to jump a long space from the rotor contact to reach the cap contacts. I'm wondering if I just replaced a wrong "old" rotor with a wrong "new" rotor. It certainly would explain the miss at higher rpms. :-\ Add this to the single ported (vs the double ported) vacuum advance and performance would certainly suffer.

Edited October 1, 200916 yr by quartus

I also noted that the replaced rotor seems "short" ie the spark has to jump a long space from the rotor contact to reach the cap contacts. I'm wondering if I just replaced a wrong "old" rotor with a wrong "new" rotor. It certainly would explain the miss at higher rpms. :-\ Add this to the single ported (vs the double ported) vacuum advance and performance would certainly suffer.

 

did you see the oem part numbers i posted for you in your other post.

Disconnecting the knock sensor took care of the stumble @ 3500 RPM, the stumble doesn't start till ~ 4500 RPM which I don't hit too often

did you see the oem part numbers i posted for you in your other post.

 

 

I did see them and have noted them but I can't find on the net how to go from part number to photo of part in question.

Had to reopen the thread, the knock sensor was not disconnected and it only ran smooth till it heated up. What could cause good cold performance and then stumbling after it warms up? I'm guessing the problem is more fuel/air based than ignition based. Anyone have experience with this issue? :-\

Try replacing the ignition coil, they are known to give these problems (stumbling when hot)

Well, sure enough it was the wrong rotor installed. I found the right rotor and the engine is now running fine.

Have to reopen thread again, the right rotor certainly helped but I still have a bad miss/stumble above 3500rpm, would this be a fuel starvation issue (new fuel pump & filter installed), ignition issue or turbo issue. The reason I say turbo is that I have a smal preturbo exhaust leak and I only get ~ 5psi of boost. This morning I also noted that I could "sneak" up to 4500 rpm range if I kept it from boosting (maintained intake vacuum).

 

If I floor it (full boost), its like I hit a wall @ 3500 rpm and can't accelerate anymore, it just misses and stumbles. Any clues anyone? :-\

Hopefully I'll self talk myself into a solution Here's the latest, no the way home I tried to see how high rpms would go without missing and with 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 ( see http://www.ultimatesubaru.org/forum/showthread.php?t=103540 ) I don't think it would cutoff the pump anyway.

 

Any more ideas Subaru Masters?