I have a 95 f150 5.8l v8 that has been parked in my garage for 8 years and I've recently started it up a few times. Right after it starts up it doesn't seem to run smoothly, you can hear a clunking sound and the engine shakes a bunch. I changed the oil and put a additive in the gas and oil to clean the system and remove carbon build up ect. I also took all the spark plugs off and cleaned them. After doing all this the noises seemed to quiet down a bit but it is still there. I have a feeling it is a vacuum leak but I'm not totally sure. Has anyone else experienced this? Do any of you know what it might be? Any help is greatly appreciated. Thx in advance

 

I'd suspect the injectors are gummed up, and not all of them are opening, creating misfires. That's what has happened to every engine I've cranked after more than 4 years, including the '95 F150 I'm working on now. In each, I had to short each bank of injectors to ground to warm them up so some gas could flow & wash the gum out. Your truck is probably SEFI, which means only the ones that are misfiring need to be shorted. To ID them, let the engine idle & momentarily disable/disconnect each spark plug wire at the cap (you can use a common 12V test light with a sharp probe to pierce the boot & short the spark). If it has no effect on the idle quality, that cylinder isn't firing anyway. Each injector has a Red wire, and another. Use a pierce probe to momentarily (~1-5sec at a time) short the OTHER wire to ground. Do that to each injector whose cylinder didn't respond to the spark test until you notice an improvement.

If you're not comfortable with any of that, take it to a pro.