What is causing this engine stumble? (video)

[Cogswell]

Originally Posted by Grad

Thanks so far everyone.

I have Googled the crap out of this and turned up completely empty. I have threads running on both Tiger boards and nobody has seen this before. They all agree that this is not normal behavior at all. I have loaded several different fuel injection maps and it hasn't changed the problem. They are giving me some ideas to check out, but nobody is certain what the issue is. My TPS is a little out of spec and I do have a high idle (1600 instead of 1150 rpms), but so far most feel that the TPS wouldn't cause this particular problem. I will try to fix the TPS, but I am trying to gather more information before I tear the bike apart (tough to get to the TPS) so I can check other things that could be the culprit while I have it torn down.

I was laying awake last night trying to figure out what the issue is, and I have come to the conclusion that this isn't some little engine miss or misfiring spark plug. It is way too abrupt and final. Essentially, it is like the bike is in decel mode for about a second. It isn't missing, it isn't stumbling, it is like I chopped the throttle completely closed, waited a second, then resumed exactly where I left off. Perhaps like something builds up, releases, then starts to build again. Any idea at all what could cause this?

Correct your high idle problem first, then see if you still have the stumble.


Mike

[Kiwirich]

Have you checked for Air leaks in the Intake tract ? Cracks in the ducts etc

It does sound like fuelling,

[Grad]

I hate it when I am researching a problem and come across a thread where someone asks a question and never updates when they get it fixed, so...

It is all better now

Two separate issues...had to replace the TPS and stepper motor to fix the high idle, and then a coil was causing the stumble. Strange symptoms, but all better now. Thank God for cheap parts on eBay