I have a 2003 Honda Civic DX 1.7 5-speed. I replaced the timiing belt and changed oil and filter on 7/19/2010. After that it idled slower and slower the more you drove it. I attached it to sensor and it showed (MAP) sensor was bad. I replaced (MAP) sensor on 7/23/2010. Now it is still idling slower and slower the more you drive it and it is dying if you take your foot off the gas. It has no get up and go, on the highway I had the gas to the floor and maxed out at 50 mph. I put it back on sensor and it showed P1129 (MAP) sensor circuit higher than expected and P0505 Idle control system malfunction. Any ideas what is causing these problems or how to fix them. Please and Thank you.

For your idle control problem, try cleaning the IACV, throttle plate, and throttle body:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1054149

Afterwards, clean the air box and install a new air filter. This may eliminate the codes being thrown. Clear the codes with your code reader. Start using full-synthetic engine oil (e.g. Mobil 1 or Pennzoil Platinum) and changing the oil and filter every 6,000 miles or 6 months, whichever comes first. This will allow your engine to run substantially cleaner, including PCV Valve, EGR, and all emission systems.

Just for grins, take a strobe light and check the timing.

Beside cleaning the IACV, replace the PCV Valve and clean the PCV Valve hose, which contributes to crud in the plenum. Synthetics will help this big time.

Because of the recent work, ensure all electrical connectors are properly connected. Look over everything under the hood.

Beside cleaning the IACV, replace the PCV Valve and clean the PCV Valve hose, which contributes to crud in the plenum. Synthetics will help this big time.

Because of the recent work, ensure all electrical connectors are properly connected. Look over everything under the hood.

Thank you very much for your suggestions.