Rough Idle

[Locomoko]

I just picked up an MSP (yay me). It's been flashed and still has the clunk (scheduled for some lovin at the Mazda dealer next week). While I don't really feel much stumble or hesitation with city driving, I do feel significant hesitation at partial throttle (and full throttle, tho I RARELY WOT) when at highway speeds in excess of 60mph. The car feels like it absolutely can't accelerate beyond 85mph on a smooth flat road.
At a stoplight, the car will often be fine, then stumble sleightly. Occasionally the RPMs will dip down a little below 500 and then smooth out at 700-800ish.

The car currently has no mods and the mazda techs said they "couldn't find anything wrong with it". All they could suggest was that the car might stumble a little when the AC is first turned on. (This is news??)

I'm thinking of putting in a set of Denso KJ22CR-L8 (extended reach, copper, one heat range cooler, .8mm gap) plugs to see if that helps smooth out the idle and perhaps help with the high-speed stumbling issue.

Could joe's FCD help with this problem? Should I also install his FPR kit?
My MSP is flashed, but I still find a lot of carbon in my exhaust's tailpipe (I clean it every other day to try and gauge how quickly it builds up), so perhaps it's still way too rich even though this carbon buildup is happening without any WOT driving.

Thanks in advance for your suggestions!!

 

[Liv2ride21]

I own a P5 so I don't know about the stumble/clunk at speed, but I've definitely had the same problem with idle hiccup. I haven't really used the A/C (just dash vents), so I'm not sure what cuases it either.

It's like the car wants to stall all of a sudden for no reason but then catches itself and stablizes the idle.

 

[Locomoko]

I have the stumble whether the A/C is on or off (A/C is usually off anyway cause it's not too hot here in Hawaii). (spin)

After I get a tune and swap in the denso plugs, I'll report back my findings if it helped or not.

 

[PR54LIFE]

I also have the same problem

 

[All Boost]

Fuk sakes. There is a million people with this problem. I wish mazda would clue in and fix the problem. Here are a few and i mean few possible causes.

Alternator sux - When the Fan kicks on, and it usually happends when it does. You get the poor idle.

Battery sux - Some people have put in Yellow caps but see no results, so save you money.

MAS/intake - when the fan kicks on, it blows hot air to the air box. The sudden change in intake Air temp makes the computer recalculate stuff. This might give the poor idle too.

Grounding kits - some say they help, i donno. i think the whole situation sux. my car shouldn't come close to stalling. once and awhile the engine light even comes on.


MAZDA, if your listening, Fix the s***, before i become a mechanic, fix it and shove it in your FACE.

I'm ok, i swear.