My first car was a 1991 Plymouth Acclaim with a 3.0L V6. It started having some problems by the time I got it, and my father and I replaced every component in the fuel system, from the tank to the injectors until we found what part had gone bad.
It was a relay switch that cost $5.
It wasn't that funny at the time.
I know it wasn't. I had a '74 Gran Torino with a 351. I rebuilt the carb and it ran great. Until I got to about 45 MPH. Then it died. If I took my foot off the gas for about five seconds I could then get it up to about 55. I could keep doing that until I hit at least 90. Unless I was heading into a strong headwind. Then I could hardly get it up to 50 and keep it there. I was sure it was the fuel supply, but couldn't figure out where. I replaced everything in the fuel line, from the filter on the intake in the fuel tank, the regular fuel filter, the fuel pump, and for good measure, just in case I was wrong, I replaced the plugs, plug wires, points and distributor cap. I had the top off the carb and adjusted the float at least a dozen times. I really felt that was where the problem was, but couldn't see a damn thing wrong. I finally took it in to a Ford garage, because I was going to be towing a trailer, and there was no way I was going to be able to with this problem. We told the service manager what the problem was, and he said he would have someone take a look at it. My dad had gone with me, and we were looking at the cars on the lot when we saw a mechanic coming back with my car after a test drive. We went back to the service dept. to talk with him, and he was glad we did, because everything I had done was what he was about to do. This was their master mechanic, who had his own separate bay. He caught what the problem was. When I rebuilt the carb, the needle/seat assembly screwed down with a washer under it. The original had a splash guard built into it, the rebuild kit had just a plain washer. I had put them both on, since they didn't look the same, I thought they both needed to go on. The few thousands of an inch of the extra washer added just enough height for the tang to hit the gasket, when the top was on the carb body. When the top was off, when I was adjusting it, it worked great, nothing for it to hit. Took the extra washer off, and the thing went right to 100 without a pause. Ran great with all the new parts.
The mechanic put on a new float just in case, and I think the shop charged me about $10. More than happy to pay it.