Bought an 89 na vert about a month ago. 152k miles with a reman engine rebuilt a few years ago. Has full catless exhaust. Still has good compression. The issue started the day I test drove it, one time out of several wot 1st gear pulls to redline it cut or broke up at 7k rpm. It only happened once and every other time it went all the way to 8500 smoothly. It had a cel when I bought it and figured it was the tps because the idle was a bit bouncy (goes from 800-1500 randomly ,it doesn’t really surge it just is either at 800 or 1500). Checked the codes and it had codes 8,9,10,11,18. For the afm, tps, and water thermosenser. The cel will randomly come off for like 20 minutes and then back on while driving. That leads me to think it’s a grounding/wiring issue. Now the breaking up issue has gotten worse, it will now breakup cruising in 5th at like 2-3k rpm and also in 1st and 2nd at 2-3k rpm at like 50% throttle and it happens more frequently. I don’t think the cels are connected to the breaking up issue because it drove so well before with the cels. I’ve had one or too close calls to flooding (shut it off while hot not cold) so I think it could be an ignition problem. Any suggestions, tips or help would be greatly appreciated

 

Video of breaking up, happens in 2nd at 5500