'86 Volvo 245 Stuttering when at temp

I have an '86 245 with an intermittant engine stutter for the last several months. This only happens after the car has been running for about 20 minutes or on a hot day. It will stutter for several seconds (some times die) and then function normally for the next 5 to 30 minutes before it stutters again.

The car was tuned up about 1 month before the problem started

I replaced the fuel pump relay, did not help. The shop told me the in tank pump was bad so they replaced that. This seemed to fix the problem but a month later it started to do it again.

Any ideas?

Thanks,

Papa Jim

If the fuel pump was running normally, the relay was at best a WAG, which clearly did nothing. Fuel pump was replaced...how about any filter?

Chase