So I'm getting a stalling feel if I tap the gas, the RPMs return too low and almost stall. I guess I'll start with spark plugs. Am I ok with Bosch 4+ Iridium Fusion? They're new from Bosch, I have them in my 540i and it made a difference from Bosch 2+, but anyhow are those alright to use? What else could cause this?

 

Stick to stock NGK pfr7g-11s I believe.

 

Leave the stock plugs in...trust me on this. Pull them out, make sure they are the factory nkg PFR7G-11S, make sure they are not worn, then put them back in and TORQUE THEM PROPERLY. A loose plug on this engine is catastropic. If the plugs have 85k or more, change them with factory plugs. Buy them at Honda.

Your idle issue are likely a sticking IAC valve.

This thread reminds me of many where one problem was causing an issue, the incorrect part was serviced, and the car just went downhill.

 

I run NGK V-Power copper plugs in all my cars listed below.

My 03S likes either the NGK BKR6E or 7E.Gap @ 44.

Since it only takes about 30 min & $10 to change these 4 plugs,I pull & replace every 10k miles.

\rlr
carolina

 

Bosch plugs don't work so well in Honda engines, I would never run them in this engine.

 

Your 03 is the same as all the 03s I work on. They all use stock, and "like" them for 80k. The gap is set at .039, what the coils were designed to operate at.

Aluminum threads have a service life. Changing plugs that often is asking for trouble.

 

Let me start by stating any and all inputs from B-Man I have found to be second to none. Trust his input on plug selection. That said I read your specific question a little differently and feel the plug is a red herring. If I understand your input correctly if you blip the throttle you find it drops below the expected RPM range and just about stall before recovering to a normal idle. This issue is common, regardless of plugs installed. It is related to to an imbalance between your long term and short term fuel trims (LTFT vs STFT). Usually this comes up with changes to the weather pattern or cars coming out of storage but it appears you are in Arizona. Done any driving recently in higher or colder climate? This can set up the issue you noted, is very common, and will return to normal when the LTFT and STFT come back in balance. Can't recall the number of hot/cold cycles it takes but it should clear up in a week or two on it's own if that is what has occurred


Utah

 

I've never thought of the aluminum thread issues, but I also run the V-powers and change them every few oil changes... Anyway, Bosch +4s are the worst plugs ever. Every single car I installed them in developed a misfire. I'll never trust bosch again because of those shitty +4s. I honestly would now rather run copper autolites then bosch platinums. Gimmicky product.

 

For the record, I am no mechanic/technician whatsoever. That said, I bought my S while living in Tucson, AZ and ran it as a DD 5-7 days per week through one summer and found the exact same problem. The issue was much more exaggerated at stoplights on hot (110-115 degree) days. I didn't ever do anything to try to fix the problem after reading several threads of a similar nature (esp. related to heat-soak). Now, I have been living in Denver for about 6 mos. and have almost never experienced the same problem (only a few times at idle on hot (80-90 degree) days. Just my $.02 coming from the same climate.

My solution, take a vacation to Flagstaff (my hometown) for a week and see if you have the same issue.

 

This is a very common problem and I've noticed it on many Hondas, many people refer to it as a brain fart, but it could very well be fuel trim related. It almost seems that the pcm and sensors just take a brief break from doing their job and then they gather their composure and things return to normal... lol.