Hesitation and rough idle - sometimes

My '98 with 150k miles started acting up the other day. It had all the symptoms of a bad fuel pressure regulator. It had the hard starting (that had been going on for a year or so), engine surges while stopped at a light, lack of power and hesitation while accelerating, etc. I did not have a fuel pressure gauge to check the fuel pressure. The part was cheap and easy to replace so I changed the FPR last night. The car ran perfect for about 10 miles and then started acting up again. This morning, while driving to work, it was 75% better than it was before. But, something is still not right. It starts right up now, idles a little rough at stoplights (unless I put it in park or neutral), and doesn't hesitate nearly as bad when I take off from a dead stop. There is no hesitation now when accelerating from say 50 to 60 mph. Any thoughts?

Sounds like a bad plug wire. You probably should do a tune up, plugs and wires.

Someone I work with had suggested the plugs and wires. I have not looked at them yet. The only thing with that was I would think something wrong with a plug and/or wire would affect the engine all of the time. Also, why did things get 75% better by changing the FPR?

I thought you said it was idling rough at stop lights and having trouble accelerating. I assumed you meant all the time. When was the last time the plugs and wires were replaced and what were they replaced with?

It does idle rough all of the time. It does hesitate on acceleration all of the time. But all of that smoothes out once the engine is not under a load and I am just cruising at a constant speed or I drop it into neutral or park. If it is missing and/or having spark issues, wouldn't it miss no matter what load the engine was under or what gear the car was in? The plugs and wires have not been changed recently. I will probably do that this weekend as well as a new air filter. Thanks.

no, it is much more likly to miss under load. Faulty wires are high resistance, or open circuit. Under light load the coils can fire, under heavy load they can not.

I ended up replacing the plugs and wires this weekend. Not too hard of a job. This took care of my problem. Thanks.

Awesome!