89 Lesabre, long start, popping at hwy speed

My 89 LeSabre (225k miles)doesn't always start right away and is getting progressively worse. The idle seems a bit rough when it does run, will stall when coming up to or at a stop sign. Seems to be popping out the intake at hwy speed, blew the cover off the air cleaner housing, pops so bad, have to shut it off and hope it starts again. It does run descent when its warm, above 50 degrees. Put a fuel pump and new coil pack. Unplugging IAC doesn't help. No codes are showing. Any ideas?

Welcome to AF. Check the plugs and wires, sounds like a misfire or bad valve in the engine, may have to do a compression test also.

It could also be a stretched timing chain. Would you happen to know when it was changed last? More than 100k miles ago?

Im betting on the timing chain.. sorry..
With that many miles.

To backfire out the carb/intake.. a valve has to be open when the spark meets the gas either by valve timing or bad valve or spark jumping to it at the wrong time.

Good Luck