I have an 01 Civic that is almost completely stock and I had a 30K service at an independent shop and ever since then the car runs like crap. Sometimes when the gas pedal is depressed, the car stumbles on acceleration and it just seems to lack power. The gas mileage pretty muched stayed the same. I check the spark plugs and they are good. Other than that, I don't what else to check. Isn't timing computer controlled?

 

Do you have a CEL on?
There are some other basic tuneup stuff you prolly have not done...
Spark plug wires
O2 sensors
Tranny fluid and filter
Air filter
Gas Filter
PCV valve

If you are reaching 90,000mi change the timing belt and tensioner...Mine has 65,000 and will change it next weekend just for preventive issues...

When I bought my car I thought it was Ok until a did the tuneup myself and poured a couple of injector cleners...NOW it is OK...it got a lot healthier after I did the tuneup...

 

Well considering that my fiancee is the original owner and the car ran fine until she brought the car for the 30k service. I didn't drive the car until maybe a month after the service and noticed that it lacked power and that sometimes it hesitates on acceleration. I check the spark plugs and they were platinum plugs when they were iridiums originally so I replaced them with iridiums and the hesitation was still there so I am assuming its either a sensor or fuel pressure.

 

01+ do not have a distributor so spark plug wires don't need changing. O2 sensor should throw a light if they are bad. Air filter could be a culprit, could check the air box and pipe see if anything may be clogging them. 01+ also do not have a return line so fuel pressure should not be a problem, unless your pressure reg at the rail or the pump is bad. Keep in mind that the 01+ don't make good power, hesitation on acceleration could be due to tranny problems, I've heard stories of bunk trannies might consider taking it in for a tranny inspection.