Erratic Map, Erratic AFR

[morris]

Hello All,

I am hoping you can help me troubleshoot a new problem that has come up. My MS install is a 79 MG Midget with single point TBI adapted to the stock carb. I am not controlling spark at this point. It was running quite well until lately.

Now the map jumps around by 5 or so Kpa which causes pretty erratic AFR at highway speeds. My map is set up so that I am running 14.5 at 60 but 13 at 70, so this coupled witht the erratic map, may be the cause of fluctuating AFR.

The problem started about a week ago, and would only occur randomly at highway speed. The map would be stable, then bounce around, then be stable again. Now the problem occurs at all speeds and idle. However, map is stable on decceleration.

Any suggestions as to where to start troubleshooting?

Thanks!

MS I v3 running MSnS extra 029q