RPM Fluctuating on STi

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I had noticed recently while driving a sensation like my car was "surging" but didnt pay it much mind until yesterday. I was outside in the car and if i hold the rpms steady anywhere above idle it will drop 500rpms then rev back up while maintaining constant pedal pressure. The same thing happens while driving and a constant speed while cruising just not as noticeable. The car revs up ok and accelerates good it only seems affected at a constant pedal pressure. Any Ideas?
 
I actually just ran some redline through the tank. No codes or cel. Say i rev it to 3000 and hold it, it would drop to 2500 then back to 3000 continuously.
 
Originally Posted By: Papa Bear
Is this fault with the '04 or the '94 Accord ??...


Its on the 04.

I am thinking it may possibly be a faulty maf sensor I have known of them to go bad but in a way that doesnt throw a cel. Or possibly a tps but this car has throttle by wire and doesnt have a tps on the throttle body like most do.
 
Last edited:
Originally Posted By: SubyRoo
Originally Posted By: Papa Bear
Is this fault with the '04 or the '94 Accord ??...


Its on the 04.

I am thinking it may possibly be a faulty maf sensor I have known of them to go bad but in a way that doesnt throw a cel. Or possibly a tps but this car has throttle by wire and doesnt have a tps on the throttle body like most do.


+1
Clean the maf first (with the CRC stuff).

Could any of your Cobb mods have affected this in any way??
 
I cleaned the maf. No good still pulses. I dont think the tune would have any thing to do with it, it has had the tune since 2006 and this problem just popped up in the last month. I have been told to replace the fuel pressure regulator and/or the front and rear O2 sensors.
 
Boost hoses failing?

I see many turbo cars get a boost hose failure, and get all kinds of power losses.

If a hose fails downstream of the MAF, unmetered air goes in and makes the engine run lean when there is no boost. Then when there is boost, more air gets pulled from the MAF than what goes in the engine, causing a rich mixture.

Check your blow off valve. If it stays open you will also have problems related to boost. Also check if the BOV hose that recirculates air behind the MAF is good. If not, the engine will run rich as you take your foot off the gas pedal.
 
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