Why does engine still skip after EGR and IAV valves replaced?

Question

My 2003 honda odyssey started skipping at light acceleration, maybe 40-55 mph. I cleaned the EGR ports extensively. Still skipped and gave codes p1491, P300, P301... as if spark plugs were not working. I replaced the egr valve. Still skipping. I watched internet videos and look up forums. Some said air may be in coolant system, some said fuel injectors may be clogged. (Engine accelerates fine, andhas no problem at all when engine is cold. Once engine warms up, skipping starts and at erst at a stoplight, engine idles way down to only a couple hundred rpm, some times surges.) Some videos said to "re-learn" the computer by starting engine, running at 3,000 rpm for 5 minutes, then turning on air conditioner for 5 minutes, then running as normal. I did the "re-learn", purged air from the radiator/coolant system (yes, many bubbles came out after several minutes). I poured a bottle of fuel injector cleaner into the gas tank (the engine ran horrible after that until that tank of gas was gone). So more videos and forums, and some said IAV valve must be bad. So I replaced the IAV valve. I tried to check for vacuum leak in the hoses by spraying soapy water all over the hoses while the vehicle was running. No bubbling or sucking appeared. I didn't want to try with gas/propane as suggested on some videos for fear of starting fire. I have cleared codes several times but P1491 keeps coming back on and engine still skipping once it warms up and has low idle. Going on 1 month of this trouble...Any ideas????

Answer 1

P1491 mean there a problem with the EGR lift.. What the EGR is is the exhaust gas which has already supported combustion is reintroduced into the intake because it is carbon monoxide it does not support combustion. . If there was no EGR or the EGR disabled you will not have a skipping engine . you would need to determine if the misfire is EGR related. The EGR is a important device beside controlling Nox which is a pollution. it lower the combustion chamber and prevents spark knock. run a engine  on a long drive without the EGR you can guarantee a hole  in the piston. The only way you can clean out the EGR port is to remove the upper intake there you remove the carbon build up.

Here a TSB for this code just FYI

SOURCE:
Honda Service News May 2003

TITLE:
Surge or Hesitation at 30 to 60 mph:

APPLIES TO:
1999-03 Odyssey

SERVICE TIP:
On 1999-03 Odysseys, a sticking EGR valve can cause the engine to surge or hesitate between 30 and 60 mph. This can easily be mistaken for an A/T problem. To check for a sticking EGR valve, do this: