85 GSL-SE Engine Stumble

[dyckvk]

Does anyone have thoughts on how to cure a below 3300rpm engine stumble in a 13B rotary?  I've checked the internet and there are discussions on checking ground wires, rebooting the cpu, checking fuel injectors, etc.  I've replaced the fuel injectors and replaced all the distributor internals.  Above about 3300rpm the car runs beautifully and pulls hard to the redline, but below that it seems to be missing and chugs along until you hit 32-3300rpms. Thanks!

[~Groll69~]

i want to say that it sounds like the timeing may be off by just a hair. 

Grounds from the engine to the chasis are important and chasis to the battery.  ensure you have some good ground connections.

When exactly does the engine stumble?  it really could be a small vaccum leak somewhere cuasing the issue.

[Kentetsu]

Location?

[dyckvk]

Thank you for the thoughts. I'm in DeWitt, just north of Lansing.  The car starts good, idles pretty well particularly after it's warmed up.  If you rev it in neutral it is nice and smooth.  But if you put it in gear and accelerate, it stumbles and misses until you push harder on the throttle and get the revs above about 3200rpms.  Then it smooths out and is great all the way to redline.  I'll see if I can get more specific about the rev range that's the problem.

It started last fall after I'd had it a few months and had run it on some longer drives (70-80 miles) to see how it held up. 

[ITSWILL]

I had an issue like this and I kept thinking it was fuel, replaced the filters and the pump. It turned out it was the spark plugs. Check them out if the center electrode is spherical rather than perfectly cylindrical I would replace them.

[Kentetsu]

Ass air flow sensor?  Maybe it has some deadspots.  There is a method to check for linearity issues, but I don't know what it is off the top of my head.

[~Groll69~]

I know the plugs were different in the 84 and 85 13b's to the 2nd gend plugs in the 13b's.  you may need to use some sandpaper and re-gap the plugs. 

I am learning alot working on this 84 GSL-SE i have in my garage.