Dipping Idle problem?

[Ryoga28]

For the past two or three days, I've noticed that my car would dip to 500 rpms when coasting to neutral. It doesn't matter what the rpm is (blow off or not). I'm currently running a dual setup (stock bpv, greddy type s with three threads exposed). Never had this problem before until recently.

Yesterday, I changed my spark plugs and did a seafoam injector cleaning and noticed white smoke coming from the exhaust manifold area...This never happened to me before.

Possible problems I can think of at this time is a leaky vacuum hose, cracked manifold, or bad gasket between turbo and s pipe (recently had my mechanic install the GHL dp).

Has anyone else encounter this problem before? any solutions?

 

[terbow]

I have dipping idle too. Im recirculating. Ive had it for so long. Even with stock stuff. Perhaps it was post GHL tho, i cant remember that far back.

I havent solved it yet. In fact i Havent had time to even look at it.

 

[MSP #167]

thread jack.....but how many miles do you have on your car that you performed seafoam on it?

 

[Devilspawn]

subscribes...

I had this happen to me this weekend on a 2 hour trip, and my car is stock...

 

[Ryoga28]

thread jack.....but how many miles do you have on your car that you performed seafoam on it?

about 16k. I use seafoam about every 3k.

 

[Paul]

mine does this

 

[CasopoliS]

I also get the dips.
Where do you put the seafoam? Just put a vac hose in the can? I bought the stuff a while ago but never cleaned out the top end. Thanks.

 

[Ryoga28]

I also get the dips.
Where do you put the seafoam? Just put a vac hose in the can? I bought the stuff a while ago but never cleaned out the top end. Thanks.

I attached a hose extender to the vac hose that goes to the pcv valve. It works very well.

 

[Ryoga28]

Cap-did you get the dips with the blow through maf setup? or did you notice the dips after you install the ghl pipe?

 

[Paul]

actually mine doesn't do this since i moved my vacuum lines to my booster line & have the T fitting from the wastegate to the bottom nipple on the greddy.
only downside is 10psi.

 

[Ryoga28]

actually mine doesn't do this since i moved my vacuum lines to my booster line & have the T fitting from the wastegate to the bottom nipple on the greddy.
only downside is 10psi.

You still haven't fixed the 10psi?

 

[Paul]

^^nope not yet. but my idle doesn't dip as much as it did. you should try my setup, 10psi is fun

 

[Hughes412]

I don't think it's a turbo related problem. It seems more of a mazda problem. I get this same thing. It got to the point were it would almost die. I put in the MP3 ECU and while it still dips it doesn't do it as bad, you almost can't feel it. I noticed this started happening after I put in the CAI. I wonder if the vac-line to the valve cover is to short?

 

[Spooled]

Is there a possibility that the hotwire MAF that Mazda uses could be the cause? I would like to see a spreadsheet of everyone on the forum with these columns:

Member name
Car
Idle dip problem (yes/no)
Stock intercooler (yes/no)
Stock pipes (yes/no)
MAF or MAP
Relocated MAF (yes/no)
Spark plugs
Intake setup
BPV, BOV, or dual
Stock ECU (yes/no)
VTCS removed (yes/no)
Stock exhaust manifold (yes/no)
Mileage

The reason I left things out like exhaust and such is because I have aftermarket exhaust and it didn't fix anything.

If someone has time, it would be nice to have a MySQL DB table setup and a questionnaire page hosted that we could link to and collect that info. That way we could see patterns easily.

What do we know about it so far:
1. It only happens at idle. Touching the gas slightly stops the problem.
2. It only happens when the engine is warmed up.

What we need to know:
1. Do people with the VTCS removed have the issue?
2. Do people with hard pipes have the issue?
3. Does a better intercooler stop the problem (super hot air at idle???)
4. Does relocating the MAF help? Maybe the MAF gets a bad reading at idle because of inconsitant air movement at idle.
5. Who are the people that DON'T have the idle dip problem? If we figure that out, we can see what they have in common.

When the car is idling, the ECU is shooting for stoich. If it's getting a bad reading from the O2 sensor, that could cause it to fluxuate. For instance, maybe the uber rich environment is killing the O2 sensor and making it difficult to get readings at low exhaust speeds. I'd like to see if starting with a fresh O2 sensor after tuning the engine fixes the issue.


Just a bunch of rambling to hopefully trigger an idea.

 

[Hughes412]

I wouldn't think it's the o2 because mine did this with the stock exhaust (with the wagner shory header). What would be nice to know is how many people that have this problem have an aftermarket air intake system.

 

[CasopoliS]

Cap-did you get the dips with the blow through maf setup? or did you notice the dips after you install the ghl pipe?

pretty much occured every once and a while on every setup. Mostly with the AC on. Right now it is idling good.... so far. This morning my ECU was still learning from my late FMIC install... and it was idling at 3.5k with a cold engine!

 

[msp35]

I too notice the idle dipping @ times. Whether it's coastig or just sitting @ idle. it'll idle anywhere from 500 to 1200 rpms. Sometimes it'll try to stall but catch itself and correct it. Only running a GHL DP, K&N drop in and 10psi, colder plugs. It did this even when I was all stock though.....I say it's just part of mazda's bad tuning.

 

[Spooled]

Mine did it with stock intake and stock exhaust, and also with 3" DP back exahaust and a cone filter. Is there anyone that does NOT have this issue? That would help a ton.

 

[apocman]

you may want to take the heatshield off of your exhuast manifold and look for a crack. T-99 and a I think a few others have had cracked manifolds, as a matter of fact T-99 is suppose to get his replaced this week at the dealer.

 

[Spooled]

Mine had a bolt backed almost all the way out a while back. I was actually looking for cracks at the time because it sounded like an exhaust leak. I still get the idle dip after fixing that.