Rough idle due to stuck EGR -- need feedback

[KrayzieFox]

I drove my car yesterday for the first time in over a month, and a couple minutes into the drive I pull up to a stop light and it starts idling like crap. I had to keep my foot on the gas to keep it from stalling -- RPM were dipping down to 200-500 range, vacuum was bouncing around -10 inHg, and AFRs were in the 17's -- it was choking, sputtering, shaking.. worst idle I've ever experienced.

So I start to head back home and it goes away, then it comes back, then goes away for a while, then comes back again, and finally I get a CEL. I pull into an Auto Zone and they read it as P0401, insufficient EGR flow, which I wasn't too surprised at but I wanted to ask you guys to share your experiences with clogged EGRs. I had it happen on my P5 and the idle wasn't nearly this bad, it was more of a hiccup as I remember, the car would nearly shut off yesterday!

I also wanted to see if anyone has installed the revised Canadian EGR with the coolant hoses and had success in eliminating this problem. I know when I clean the OEM valve it will just get stuck again, so I will gladly spend $100 and get rid of the problem forever if the new valve works as well as it's supposed to.

 

[CHIQLES]

Get the canadian in anycase and then you can forget about the egr..

 

[KrayzieFox]

Yeah I'm going for it.

If anyone else is interested I found a pretty good deal on eBay. $80 shipped and it includes all the parts.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=400144751082

 

[justanothermp5]

EGR insufficient flow? that wouldnt cause the bad idle, that means its stuck closed...
should be some other code for EGR..maybe there isnt lol

but yea, whenever i stripped one of the EGR bolts off in the intake mani...my idle was terrible, just like you said
if i didnt keep my foot on the gas it would stall out, i had to add gas to the fuel map on my SSAFC just so it would idle normally

 

[KrayzieFox]

What do you mean you stripped one of the EGR bolts?

And I do remember having this code before on my P5. And I also discovered after taking off the EGR valve today that this is the exact same valve from before. I swapped manifolds when I bought the MP3 so the EGR valve is my old P5 one. It's all sorts of stuck with deposits, it was stuck closed but if I pushed it open then it would be stuck open so I'm guessing that's what was going on with the idling issue coming and going sporadically. It probably kept getting stuck in one position then the other.

Either way, new EGR valve is ordered cuz it needs to be done. But I would like to at least make sure this will fix my issue.. any other input??

 

[justanothermp5]

there are 2 bolts that hold the EGR to the intake mani, one was stripped when i bought it off the forums
and it was leaking there so pretty much the same as having a stuck EGR

the EGR is the only thing that causes a drop in vacuum like that at idle really...unless you have a split vac hose somewhere
so once you replace it, you should be good

 

[powderider87]

I have the Canadian version and mine still idles crappy every now and then when it's cold out.

 

[black daliha]

carbon deposits are a big thing on cars today. Turbo engines usually build up carbon even more. Usually around the 70-90 thousand mile mark your engine can get problems just from carbon build up. It also gets into ur egr. To be pro active its best to get a full system clean every 30,000 miles it needs to be injected through the fuel rail and into the intake manifold. Mazda even made thier own cleaner for it.

 

[yudkib]

carbon deposits are not a problem on most cars like they are on the MSP. find me another car that runs 9.8:1 AFR's, i bet they have problems too.

 

[black daliha]

the more effeciant cars get at removing the hydrogen from carbon the more carbon deposits u will get. You can get this problem on boosted cars. Some cars are worse then others but fuel system services are now becoming more important. And i dont meen adding a bottle of stp to your tank

 

[yudkib]

what are you talking about? you understand the combustion process, right?

C8H18 + O2 => CO2 + H2O + Energy.
its not exactly what happens (gas isnt pure octane but its largely hydrocarbon based) but close enough.

the fact is - energy isnt derived from stripping hydrogen from carbon and burning it, its a totally different chemical reaction. as long as there is sufficient oxygen for a given amount of fuel, there should be zero carbon build-up. when there is insufficient oxygen - running rich, deposits get left behind.

 

[black daliha]

ok im not arguing. I am just stating that that carbon build up can be a problem and is indeed a problem on our engine. The carbon can get to the egr and stop it up and stick it closed or shut. A carbon clean could help and is a good way to prevent pre ignition and misfires on all engines. I know it works and should be done at intervals. I know a guy who was a mazda tech for a long time and was the lead speed tech and he says the same thing. And plus you can usually do an easy FREE carbon clean for your engine so why not do it

 

[yudkib]

im not trying to argue either, but my last two cents
the problems with the USDM EGR are far more than obnoxious carbon build-up. the carbon deposits dont help, but its also poorly designed so in cold weather exhaust fumes cause condensation inside the valve which turns to rust (which is why its really a northern state problem). EGR's in FL and TX rarely malfunction. canada meanwhile had a recall on all FSDE EGR's, so theyre eligible for free replacements with the improved mazda unit.

 

[KrayzieFox]

I finally got around to installing the Canadian valve today. What a pain in the ass..

 

[yudkib]

from what i read, it wasnt THAT much more of a PITA than the USDM one, but getting those 12mm-head bolts off for the EGR is a nightmare. plus i always thought i was going to shatter my weatherpack for it, i could never get the leverage to get it off easily.

 

[KrayzieFox]

The worst part was removing the stock coolant line off the bypass valve and putting on the new one from the EGR valve. It's sooo crowded in there and it's near impossible to get to, but I managed somehow. All I had to remove was the battery and tray, and it took me a total of about 2.5 hours, so I guess it wasn't so bad. But man my back hurts from being hunched over so long lol.. I'm gettin old

By the way, CEL went away and the car runs and idles like a champ again.

 

[powderider87]

Yea the bolts for me weren't the hard part it was adding the coolant lines in and such.