Low idle and possible overboosting vacuum/boost leak?

[jumaaneface]

Just recently purchased a 2003 mazdaspeed protg sitting at 117k miles.

Past week for so I have been having issues with low idle. When car idles rpms will dip and stay steady at 200-400rpm. Same takes place when moving and shifting into neutral. Has yet to stall at any point during any of this so I'm taking that as a possible good sign?
Second issue is when doing a hard pull, occasionally she. Shifting from 2nd to 3rd I can hear it Backfire from the exhaust.
Third and final issue would be boost spiking up to ~10psi
When under hard acceleration.

Looking around the forum I've seen numerous people with similar issues.

If my car is indeed over boosting the wga should be replaced? Or is there something else that could be wrong.

With the low idle issue I have so far replaced the plugs in an attempt to correct it but that did not solve the issue. I purchased the NGK iridium stock heat range plugs but did not regapp them. Could this be a source of the issue? Plugs I took out were also at a gap of about .044~

Any info would be overwhelmingly helpful.

Current mods that I'm aware of would be aftermarket exhaust (unaware of the brand name) and CAI

 

[jim9]

Did you ever messed with the hex screw on the tb before? If not try cleaning the EGR (theres a DIY thread). Yep, wastegate may be going out or BC (had a crappy bc before and it would overboost, now using hallman), also does the car have any cel? I've had my car from new to 120k with no idle issue at all.... Let us know.

 

[jumaaneface]

Did you ever messed with the hex screw on the tb before? If not try cleaning the EGR (theres a DIY thread). Yep, wastegate may be going out or BC (had a crappy bc before and it would overboost, now using hallman), also does the car have any cel? I've had my car from new to 120k with no idle issue at all.... Let us know.

Thanks for the response. By bc you're referring to boost controller? As of current I don't have one installed as I dint intend to up boost until I get it running correctly and replace with hardpipes fmic etc. Replaced the plugs last week with ngk iridium ones. Decided to fight my initial thought and regapped them today at. 029. Seems to idle a tad bit higher now at around 600-700rpm.

What symptoms other than slight overboosting would I get in wastegate is going bad? From what I've read the wga could be bad. Gonna check the egr tomorrow. Would adjusting the hex screw on the throttle body be a reasonable idea? A small hissing noise can be heard resonating from it.

 

[jim9]

I wouldn't mess with the hex yet, try cleaning the egr first. Also any changes made before boost spike (does it hit 10 then drop to your current psi or just keep creeping?).

 

[JDMazdaFamilia]

6-700 is the ideal idling range but if it still dips at all you have a vacuum leak, that hissing noise is most likely to be from a vacuum leak which will make your car have trouble returning to idle

 

[jumaaneface]

Spoke too soon on the idling issue. After driving and allowing engine to heat up enough it's back at 400 range at idle. Also when I pulledthespark plugs the tips were slightly black after a weeks use. The hissing noise seems to be coming from the throttle body. Would it be crazy to assume it's leaking from there around the gasket? If I were to replace it, Better to pick up a used one off a protege5 or source a brand new one?

 

[jumaaneface]

As for the boost issue. It will hit right around ~10psi but hasn't gone over that. Then it will drop back down to about 6ish psi. Is that normal for turbocharged car? First one I've owned lol I'm not used to it. Still unsure why most hosing is plastic stock.

 

[bwlknsn91]

Thanks for the response. By bc you're referring to boost controller? As of current I don't have one installed as I dint intend to up boost until I get it running correctly and replace with hardpipes fmic etc. Replaced the plugs last week with ngk iridium ones. Decided to fight my initial thought and regapped them today at. 029. Seems to idle a tad bit higher now at around 600-700rpm.

What symptoms other than slight overboosting would I get in wastegate is going bad? From what I've read the wga could be bad. Gonna check the egr tomorrow. Would adjusting the hex screw on the throttle body be a reasonable idea? A small hissing noise can be heard resonating from it.

Almost positive the plugs are supposed to be gapped at .032. As for the boost spiking, I would recommend replacing the wastegate actuator. You can check to see if it's faulty by blowing into the vacuum line leading to it. If you can feel air passing through, it is most definitely bad.

 

[Spiced MSP]

plug gap is .028-.032

 

[bwlknsn91]

plug gap is .028-.032

I stand corrected. Would that have any effect for idle whether it be a smaller or larger gap?

 

[jumaaneface]

So im back after replacing egr valve with the canadian updated version. Still seems to be idling low to me. I can hear a faint hiss coming from somewhere near the throttlebody. Also seafoamed the car recently.

 

[bwlknsn91]

So im back after replacing egr valve with the canadian updated version. Still seems to be idling low to me. I can hear a faint hiss coming from somewhere near the throttlebody. Also seafoamed the car recently.

Did you check for leaks when seafoaming?

 

[jumaaneface]

I checked for leaks but didn't see any. I'm planning on doing a fmic kit with hard pipes so that should and replacing vacuum lines since it's cheap. Car still idles low (about400-500rpm) but stays steady at that and won't stall. When warm vacuum sits at 15. Any chance it's the wga? I also have a code for vtcs and vics solenoids if that could be the cause?

Love this car but beginning to hate the stupid problems.

Local junkyardhas a626 manifold. Good idea to get to delete the vtcs and vics systems?

 

[jumaaneface]

So after months of screwing around with the car/replacing manifolds, motors, coil packs, spark plugs, installing ssafc, and a wideband, I finally found my issue.

After installing the wideband (which helped actually spot the issue) I noticed two things: 1) when removing load from the engine, the rpms would dip low enough to almost stall the car under normal driving conditions. Afr always went lean in this case. If adding boost into the equation, it would almost always stall the car out completely. 2) removing my foot from the gas pedal while in gear after accelerating would cause the afrs to hit 12-11 on my gauge occasionally stalling the car.

Two weeks ago I put a breather filter on the crankcase for a day because that hose was torn. This caused a cel p0171 for bank 1 lean at idle. What was happening was unmetered air was being pulled in at idle and causing it to lean out the a/f mixture. It would hold steady at 16.x AFR at idle. When my fans kicked on it would pull just a tad more lean. Replaced line and fixed that cel and lean idle condition.
I bought the car with a short ram intake made from an aem pipe with an extention piece to insert the iat sensor.
On my wideband every single time my radiator fans kicked on my idle would drop to 690ish and my car would sputter and cause it to lean out from 14.8 to ~15.3… replaced the sri with a true cold air intake today and completely fixed my issue.

No more idle dips no more lean. The afrs no longer hit 12afr when shifting. Why would a sri cause this?

 

[Installshield 2]

^it sounds simply that the SRI you bought with the car wasn't fitting properly, with various leaks in different places...a properly designed SRI, that is installed properly, won't do that...but you mentioned it was 'custom' to some degree? I'm guessing that was the problem.

 

[jumaaneface]

^it sounds simply that the SRI you bought with the car wasn't fitting properly, with various leaks in different places...a properly designed SRI, that is installed properly, won't do that...but you mentioned it was 'custom' to some degree? I'm guessing that was the problem.

Honestly that probably had a lot to do with it though it still held 22hg of vacuum. Only thing left to do now if figure out why I barely get 20mpg

 

[Installshield 2]

yeah, small leaks are hard to spot...as its not so much that it will gut actual vacuum, but it WILL let air in that the MAF didn't meter...and even small amounts of unmetered air will cause hesitation and problems in specific rev ranges and loads...bigger leaks are much easier, because it will do the above but also give very noticeable idle vacuum problems...small leaks; they'll have you chasing every single part in the engine bay haha...

you want a weird situation with an intake...i have the stock air box currently with a k&N drop in...i removed the damper that goes over the radiator years ago, my header was melting it while parked after fully warmed...I just installed some hotter cams...and now...i can't stall the engine by putting my hand over the intake opening to the filter...guaranteed before the cams...i could...with cams that actually make far less idle vacuum (and a crazy lope to along with it)...suction from that thing is ridiculous...and if i put my hand over it or block it, i'm guessing its pulling air in above the filter...because nothing happens to idle quality...so it must be coming in before the MAF...

So i'm in your boat...need a new intake that does leak air in above the filter haha...if i take the top hat off of the filter box, where the maf and intake tubing runs...i can stall it instantly...but the seal around the air box is junk...