Intermittent hesitation when pressing on accelerator

[kenchowder]

Not a car geek but am desperate for help.... I have a 1999 1.4 liter Berlingo that has been mostly great for ten years. For the past couple years I've had an INTERMITTENT fuel problem. Car starts up fine, idles perfectly. For about 500 yards or a kilometer it runs fine. Then AT TIMES BUT NOT ALWAYS, when I step on accelerator it coughs, hesitates. If I pull over and step hard on the gas it can backfire, and it smokes quite a bit (white smoke), and it looks like drops of liquid (gas or water) are coming out of the exhaust. The first time it happened the nearest car-repair place was several kilometers away. By the time I got there, it had stopped hesitating (the engine "coughs"); the guy couldn't find a problem. A year passed. Same thing happened next year. Again, wet conditions in late autumn. Car almost undriveable but managed to get to a repair shop; just as I pulled in, vroom vroom, it was running great again. Guy couldn't find anything wrong with it, put the engine through some tests, test-drove it, charged a lot of money and said I should get another car. It happened again, and I tried another repair shop. Same result: tests looked find. First guy said it couldn't be the fuel pump because it was intermittent. Second guy said it could be the fuel pump, but was likely the carburetor. He suggested I put some carburetor cleaner in the gas tank. I did and it ran fine for another year. Recently it's started to act up more regularly. A lot more regularly. What tends to happen is that it acts up, and I let it sit for at least an hour, and then USUALLY it's fine again. Also what can happen is that I can drive around for a while, limping, the engine coughing and cutting out (though not stalling), and then all of a sudden it's working fine again. When it starts to work okay, it always works fine the rest of the day, at least.

And now when I try using carburetor cleaner it certainly doesn't help.

So I took it to a fourth repair shop and he said he could only find out what was wrong if it was happening when I brought it in. He said it couldn't be the fuel filter (which I haven't changed in years). Not sure why not. Finally I manged to get it to the shop when it was malfunctioning. The guy pressed the gas, it coughed, he opened up the hood, and without further ado said the thought it was the "gas regulator," by which I guess he meant the fuel pressure regulator. Does that sound right to anyone here, or is he talking through his hat? How does he know it can't be a clogged fuel filter, or sediment or rust in the gas tank, or some other thing?