My '94, 5.8, 351 is missing at idle and in drive- particularly at 25-30 and then again at 60mph. It was running fine until I parked it in the sand at Pismo Beach. Did a little 4-wheeling but nothing major.
It's been in the shop for 4-days now and they cannot find the problem. Timing was adjusted, new plugs, plug wires, gas and air filters, etc. They stuck a new fuel pump on and then took it off as that was not the cause. They've had it on the diagnosis machine and eliminated all of the codes that have popped up. It's got a fresh tank with 91 octane. Today they're going to do a compression test on the cylinders and valves but I highly doubt that could be the problem.
Are we missing something here? Looking for any suggestions...