when the car is at idle.... say at a stop light or maybe just at a parked spot with the engine at idle, is it normal if the rev needle drops suddenly from about 800rpm to 500rpm and the car shudders and then it rises back to the normal level?

 

I don't think so. My P5 did it twice within a minute while coasting. I had to blip it just to keep it from dying. I have no idea what it was. However, it's never done it again.

How many miles did you have on yours when it happened? I had about 300

 

I have 13000 miles on it....
I dunno if it could have been due to stress or long haul driving cause I just took it from LA to yosemite (about 5-6 hour drive) carrying a full load, cargo and passangers.
then while stopping and parking along the roads in yosemite without turning off the engine the needle would just drop and then just rise again.

 

did you mess with the mass air flow sensor at all? my friends does that all the time, and its because his mass airflow is shot. his almost stalls out.

 

Mine usually does that, when the A/C compressor is not on. When it's on, the RPMs are usually around 800. I've also noticed it does this depending on the weather and temperature.

 

nope... nothing inside the car has been touched. I have no mods either.

 

negatize,

considering you were in yosemite, it might be possible that the amount of oxygen at the higher elevations in yosemite caused your car to flutter. just a guess. when i was at estes park in colorado, my car was sluggish because we were sort of high up and i was running 87 octane gas. if it hasn't done it again since you got back from yosemite, i wouldn't worry about it.

 

This happens to my car all the time , think the problem might be due to the idle control speed with the AC compressor .

It seems the car JOLTS and shakes when it kicks in then it kicks the rpm up slightly.

I dont think it should do this but I dont see any long range problems with this.

 

Mine does it too. It's odd because some days it does it more than others. Oh well, as long as it's not stalling, It doesn't really bother me.

Edit: Now that I think about it, I think pimpprotege69 has it right. It seems to be related to the A/C.

 

My A/C was on too when it happened.

I wonder if Mazda perhaps uses the same IAC valve that Ford uses (yeah i know, the Pro is all Mazda, but think hypathetically) . I know of quite a few of their cars that problems with the IAC going bad.

 

I ONLY have the problem when the AC is on.
Its definetly related to that.

 

hm... yea I guess both the AC and high altitude makes sense.... I was driving today in LA with no AC and it didn't happen again... hope that is all there is to it

thank you all

 

Same problem but onlywhen AC is on..drops so low you can barely hear the engine. Doesn't ever stall or shutter though.

 

This was a topic of a previous thread - Rough Idle. someone said it was a "throttle valve" adjustment.

My 5 did the same thing especially after a hard run. I disconnected my battery for 5 minutes and it really helped.

 

My ford ranger did this, and it was because the idle air control valve was dirty and needed to be cleaned. After I cleaned it the truck has ran flawlessly with the air conditioner on. later james