04 with 21k miles, just started doing this wierd thing sporatically where im sitting at a light and the car goes up and down in idling.. revs up juuuust a tad, then almost seems like its going to choke down, but comes back up to the tad high rev, then back down.. it does it over and over.. almost seems its going to cut off, but then picks back up and compensates quickly with a higher idle, then holds it for a second then goes back down to almost cuting off. its like one second high, then conk for a second, then up a second, ten down. it will just sit there and do that until i hit the gas a little, or take off. literally about a secon on the higher idle hold, and the almost choking low...No loss in power when I take off, no skipping,.. drives find outside of the odd idling when still.. it started when i had ~1/4 tank left, so i thought it might be some bad gas, but ive filled up twice now and it still happens.. probably just twice in the last 200 miles, but its still odd.

shes due for an oil change now so Ill run it by the dealer, but would love to have a little ammo on the situation when i go in there..

o yeah no CEL at all..

thanks for any help
Jason

 

vacuum leak?

 

Pull the spark plugs and check the color. If the center insulator is black, replace them. If it is brown or tan you're OK.

 

Mine does this too. I have an aftermarket exhaust and headers on, and ever since I reset the ECU, this has been happening. No idea what is going on - the ECU is a strange beast and does some weird **** at times.

 

what he said... rare times it goes between 1k and 2k rpm for a bit... after warm it goes away...

beers

 

Hum, Im not familiar with rotary engines, but it sounds liek it is a fuel mixture problem. I know a piston engine can do this with a bad mass air flow sensor, untill the ecu replaces the values with preset ones to save the cats. That or the o2 sensor is giving false readings, but that doesnt happen very often.

A vacume leak would be consistent, and since it is more intermitent thats probably not your problem.

PLEASE post the results after going to the dealer, Im curious to know what happened

Thanks

 

Guess that depends? My friends FC does this. As soon as you start up, it would idle funny, give it a little gas, and it runs okay for awhile and goes back to idling funny after awhile.

 

that happens to me only when i drive in the rain, i have the AEM CAI, so i assume the filter's wet n needs drying.

 

check for a vacuum leak.. prolly a loose tube or a grommet or something.

also check your oil level.. too much makes it do the same thing.

 

I've got an '04 MT and it has done the same thing to me but only when the engine hasn't quite reached operating temperature. By that I mean, normal operating temperature has been indicated on the temp gauge for about 3 - 5 minutes. Once the engine is completely warmed up, the problem disappears.

Is this similar to your experience?

 

dirty MAF will cause eratic idle. so will a malfunction neutral switch. if the car doesnt know its in neutral (or clutch depressed) the pcm doesnt have the necessary input to idle correctly. there is a switch on the tranny which has been known to stick. i recently had a fellow 8 owner ove rthe house. they had erratic idle. checked with the hymee and they had a pending code for low volt on the MAF circuit. cleaned the maf and cleared the pending- right as rain