Idle problems

J

jmv

Member
:
2003 MSP #1475
My car has always had a tendency, when sitting at lights, to occasionally dip the rpms kinda low, never has stalled, but you can always feel it, and it then pops back up and seems okay. Kinda sporadic. Now that i've got my A/F gauge installed, i've noticed that i'll sometimes get a consistant reading when at idle.... it'll sit on lean for 6 seconds or so, maybe more, then it'll do the RPM dip, then it'll go back to dancing happily around and idling normally. Usually if i notice this in advance, i blip the throttle and the RPM dip never happens, but i was just curious if this is common, if anyone else has this problem, and what it might be related to. One thing that struck me is that my IAT sensor is kinda ghetto-rigged into the end of an unknown filter, could that affect it??

Thanks,
Jason
 
I don't think it's caused by where you have the sensor, I had mine hanging on the outside of the intake tube by tape. It didn't do anything wierd. What other mods do you have, If its just the intake put back the stocker and take it in to the dealer.
 
don't have the stock box, came this way when i bought it. And, FWIW, its not an 'intake', just a filter on the end of the stock intake piping, like a K&N, but not. I don't really have any reason to suspect thats the problem i guess, just thought i'd throw that out there since its pretty much the only mod to my engine thats not related to the gauges i put in.
 
38,600


nOOb question: what teh EGR?? exhuast gas something maybe?? would it cause these problems??
 
Last edited:
My car does the same thing, it will just dip for a second and then return to normal. I took it to the dealer, all they did was reflash my car. It still does it sometimes. By the way, my car is 100% stock
 
hmmm. I'm not sure if i have the flash or not. I've never noticed the hesitation issue people speak of, so maybe i do. I guess it doesn't matter though, if you still have the problem.
 
bumpizzle-dizzle


anyone got any other ideas, or further comments about whats already been posted??
 
look up a thread in the how-to called EGR clean or something similar. idle issues are usually related to either the EGR, or some sort of leak. Your IAT sensor will cause the idle to be unstable if the temperature it detects is fluctuating, which doesnt happen unless you put your fingers on it. So you basically have 2 filters on the airbox, one on the outside and one on the inside?
 
no no, i don't have the airbox, theres an unkown brand of aftermarket filter on the end of the piping where the airbox would normally be. And i'll check out that how to, thanks.
 
jmv said:
38,600


nOOb question: what teh EGR?? exhuast gas something maybe?? would it cause these problems??
Click to expand...

I didn't see anyone answer your question, so here it is. EGR = Exhaust Gas Recirculation...
 
Well, it seems like the symptoms of the EGR are pretty much the same as mine, however, after reading the how to, and how much problems some people had with it, i think i'd rather get a 'pro' to do it. Do you think if i took it to mazda and told em what was wrong and told em it was the EGR, that they'd not go screwing around the rest of my car??
 
Maybe your spark plugs are shot. Right before I changed my plugs, I had some dipping at idle. That went away when I changed the plugs. I also recommend a Seafoam or Intake cleaner spray treatment directly in the PCV vacuum tube that splits in to two hoses going in to the intake. I would not worry about cleaning the EGR directly for now. I never have and used the above steps to solve the dipping idle and to decarbon the engine.
 
My miata has a problem sporatically dipping to low when coming down from higher rpm's and sometimes at lights it can be a little erradic. After looking around I've found alot on resetting the ambient idle setting in the ECU. It sounds like somebody mentioned reflashing earlier, so maybe it's a good bet.
 
jmv said:
Do you think if i took it to mazda and told em what was wrong and told em it was the EGR, that they'd not go screwing around the rest of my car??
Click to expand...

I doubt it. They will probably want to diagnose the problem. There is a good chance that it is not the EGR. There are many other things that could be causing the problem. You could tell them that you would like them to check that EGR. I asked them to check mine when I was having this idle problem, but it turned out that they replaced the Idle Air Controller. The problem stopped for awhile, but eventually came back, although it only does it very rarely now.

If your worried about them seeing mods and possibly voiding your warranty or something, then you really should replace any such mods with the OEM parts before going to the dealership. Otherwise, they will probably not touch the car for warranty work.
 
I honestly think it has something to do with the IAT sensor. I have cleaned my EGR valve, replaced and gapped my plugs, used Seafoam, installed a positive charge capacitor, etc., etc., and those things only work for as long as it takes for my ECU to get back up to speed after diconnecting the battery. I believe that may have something to do with either the sensitivity of the IAT sensor, or just poor placement/calibration. If the sensor reacts too quickly, then the ECU may be over-compensating.

My car only does it when I am at a complete stop. If I'm idling and coasting at 15 mph, it idles fine. As soon as the car stops, the idle will dip. This could have something to do with either the lack of hot air blowing past the radiator towards the intake, or maybe even the difference in coolant temp from the lack of active ambient cooling. Remember that coolant flows through the throttle body.

I wonder if people that have done the coolant bypass mod have dipping idle problems. What about people that have moved to a MAP setup? How about people that moved the MAF to the pressure side (an possibly moved the IAT)?
 
Alright damn it, now I'm experiencing the idle dip more frequently. WTF, does anyone's msp idle normally?!?! This s*** is getting old.
 
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