This is not your usual stumbling problem, and I tried searching and found nothing similar. The car only stumbles when I take off hard, or when I'm cruising in OD in the 1500-2300 rpm range. It mostly stumbles when when I'm cruising at those speeds and hit the gas hard enough not to downshift. When that happens, the car starts stumbling bad. A little history: the car spun a bearing and the engine was rebuilt to stock with a .020 overbore. I never reprogrammed the computer, and I think I have to change an o2 sensor. Once it gets into the upper rpms, it doesn't stumble, and if it does, I cant feel it, b/c it runs very good. I need to fix this problem so I can sell my car. If anyone knows what is going on, please help! Thanks in advance.

 

werd, ive got the same thing going on, my Z only has 74k on the original engine, and its in good running shape other wise.

Also my car does it only when it is warm, when I just start up the car its fine for 10 minutes or so then its does that stumbling thing.

Thanks Andrew

 

What's up, I've just fixed my stumbling problem. When the engine got warm it stumbled and backfired, even after I installed my new delteq. After checking this and that, and buying this and that, I finally broke down and bought a distributor minus the cap and rotor. The optical sensor had taken a dump only after eight months on a brand new dist. So take my advice and replace the dist., the cap is easy to remove, just go to a local hardware store and pick up a set of very small nutdrivers This is my first post, so I'm struggling, but I want to keep you from going through what i went through. I also have a purple pearl 94 m6. PS; When you put your cap on, Please seal it with a lot of rtv.

 

so this did fix the problem for you?

How much was the distributer?

 

Anybody? Do you think swapping o2 sensors will help?