Intermittent misfire running rough P0300, P0301 P0171 codes Please help if you can

Jaysdogjazz

Member
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2003 Mazda Protege5
I need some help I am loosing my mind trying to figure this out. I have an Intermittent rough idle, While in gear like at a stop light it will act like a misfire and the RPMS will drop a couple hundred and then back to normal... sometimes at the stop light it might do it a couple of times and then back to running like normal. When the motor is cold it seems to be fine.

Here is how it all started. I went to sears to get the oil changed. When I pulled out of the lot it was misfiring and throwing a P0300. So I went back in and found they cracked my air intake tube while checking to see if my air filter was clean. So I put vulcanizing tape to seal it and I thought it was working fine but it was still misfiring. So I was thinking they must have also messed up my Coil packs by maybe leaning or touching them. Being I have Autozone Coils I went down to store to use the lifetime warranty on them and get a new pair. Still got a P0300 and P0301 and it was running rough still.

So in my infamous wisdom and it being Sunday evening and I need to get to work I ran down to Walmart and grabbed the expensive Bosch platinum 4's. Ran fine for a couple of days but still had the intermittent lag / misfire. Then at about the end of the week P0300 and P0301 all the time.

So I went back to Autozone got another pair of Coils they tested bad. They guy at Autozone thought he knew everything... Funny the computer he had said to test the Resistance on 3 or 4 points its suppose to read like 3 - 4k resistance on the coil packs It was all within specs. So he grabs a new pair anyways those those were reading infinite. So then he was like I must be doing something wrong...

I went ahead got the 2 new coil packs 4 new spark plugs went ahead and got the NGK's like I am suppose to have and got a new PCV Valve.

Runs Great for 2 weeks

Now its slowly coming back again the misfire is getting worse and more often but I also getting a new Fault P0171.

I found that the Intake tube has another small crack and I picked up a new tube from O'Reilly's they have the Dorman one for $ 36.00 I plan to install this later today...

My concern is prior to this all starting back when it was like a California cold in the 50's I would occasionally get a fault saying that my Catalytic Converter was under temp. but once it warmed up the fault would go away. Could purchasing a new Upper O2 sensor be a part I need to replace next if this air intake tube does not resolve my rough idle problem.

I have also seen others post about P0171's being repaired by replacing the fuel pump and fuel filter "Fuel Sock". Should this be my next part purchase.

Any input on what to do next would be greatly appreciated and Thank you in advance for taking the time to see if you have some info that might help.
 
Replace the intake hose first. If the intake hose is this bad take alook at all the other vacuum lines while youre at and replace as needed. Do this before replacing any other parts

Normally what happens when the hose gets so rotted when they bend it to take the top off the air filter housing it will crack. Those guys should of had you replaced it right there and then. Im sure the guy that did the oil change saw it and didn't say anything thinking it was his fault. It just old change it since you already bought it.


bouncing idle normally indicates a vacuum leak. The ecu sees the map and maf reading and make adjustment to lower air flow its seeing, then it sees a drop in idle and makes adjustments to bring it back up. so the idle begins to bounce. normally almost stalling to 1.5k rpm.



Sorry im editing this as im reading what you wrote and i clicked the wrong thing on the first post.
 
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I put the New Tube in and seems to be still having the same problem but I have 50 mile drive home tonight so will see if it helps it out. I see people saying about resetting the ECU. I was wondering cause I have the Torque app for my phone and I have the Bluetooth OBD adapter, the reading are always a little lagged but I can always clear the faults on the car is that the same as people talk about unplugging the negative on the battery.
 
clearing the faults with the app and actually disconnecting the battery is not the same the ecu will store the code even after you reset it using a scanner or the app, disconnect the battery count to 30 and reconnect your 50 mile drive will be the true test on whether or not your codes come back......as far as your converter check the O2 (main) sensor and make sure its working properly, if it is then you may need to replace your converter as it either my be clogged or dirty
 
Ok so here is an update. It is running better but still doing the searching I am planning on cleaning the Intake air control valve and the EGR valve tomorrow.
 
cellP0171_zpsa508d518.jpg
 
" I have an Intermittent rough idle, While in gear like at a stop light it will act like a misfire and the RPMS will drop a couple hundred and then back to normal... sometimes at the stop light it might do it a couple of times and then back to running like normal. When the motor is cold it seems to be fine. "

Classic EGR symptoms. Recommend replacing it with one from Rockauto.com.
http://www.mazdas247.com/forum/showthread.php?123732861-Canadian-EGR-valve-exposed

You can test if the EGR is the problem by unplugging its electrical connection. This will trigger a CEL but the intermittent stumble at idle will go away. If the problem is the EGR, it should be replaced since cleaning it doesn't seem to help much.
 
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^^ it could also be from the fans kicking on. Listen to see when the fans kick on when you come to a stop. Many proteges do this. Including mine, though i havent noticed it recently. Make sure your battery terminals are clean. i also herd adding engine grounds will help.

Im pretty sure Jaysdogjazz codes where caused by the intake tube. So much unmeasured air going into the engine made it run lean. If the mixture is lean enough it'll cause the engine to miss fire. Did you clear the codes? Have any of them come back now that you've changed the intake tube? I saw you posted its running better now.

You got to take it easy on replacing a bunch of parts. Just think about the fact that everything changed when you got an oil change and all they did was change your oil and check the air filter.

The cat. i wouldn't worry about unless you have emission coming up all, that crap doesn't effect engine function. (unless they become clogged)
 
You can test if the EGR is the problem by unplugging its electrical connection. This will trigger a CEL but the intermittent stumble at idle will go away. If the problem is the EGR, it should be replaced since cleaning it doesn't seem to help much.

^^Unless the EGR is stuck at open when you unplug it.

Seafoam may help clean out any gunk that may be making things sticky somewhere.

RoughIdle_zpsf7513593.jpg


DTCP0300_zpsa8bad2b2.jpg


DTCP0301_zps0fc002c9.jpg
 
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Uhg I have been trying to figure out what to do,

I didn't do the cleaning till Sunday but on Saturday night I took the car out to go shoot some pool and on the way it started to spit and misfire and the gave me the check engine light when I got to the pool hall I read these codes P0660 P0505 and a P0421. Cleared the faults went in played some pool and drove home and no problems.

Sunday I did a few things
I decided to remove the Idle air control valve off cleaned it with carburetor cleaner but couldn't remove the Solenoid portion cause I found it had what I would call a security bit "torque's bit with a dimple in the middle" but went ahead and cleaned what I could

I tried to remove the EGR valve to clean it but couldn't get a good grip with a ratchet loosen the 2 little nuts under it so I gave up rather then stripping the nuts. Plan to see if I can get underneath this weekend if I can get a couple of longer extensions.

Cleaned up a little bit the intake and made sure all of the factory intake tubing was correctly put back together.

after all was completed I got that hair to pull the O2 sensor off and check it out. Cleaned it off and it is starting to look pretty beat up. So I am leaning towards after payday I need to get a new one.

Bottom line is I am still getting the intermittent stutter when the motor is running and in gear and now occasionally I am noticing the misfire while I am accelerating. Is it weird that in neutral or park the motor runs fine
 
You can remove the EGR from above using a bit of force with a low-profile 1/4" ratchet with a 14mm socket (or is it 12mm?). To diagnose if the problem is the EGR, instead of removing the EGR it would be simpler to unplug it (which triggers a CEL but won't do any harm) and drive around for a bit and see if the misfiring goes away. You probably want to start with this free diagnostic test before spending money on an O2 sensor your car might not need.
 
If your car runs file while driving but crappy at idle, I get a 95% feeling it is your EGR valve. It's pretty hard to get to from above but it's doable with a 1/4 drive and disconnecting some stuff out of the way. From below, it is much easier to access, you probably won't need any extensions.
 
after all was completed I got that hair to pull the O2 sensor off and check it out. Cleaned it off and it is starting to look pretty beat up. So I am leaning towards after payday I need to get a new one.

Bottom line is I am still getting the intermittent stutter when the motor is running and in gear and now occasionally I am noticing the misfire while I am accelerating. Is it weird that in neutral or park the motor runs fine

Any updates?
 
P0660 - Variable Inertia Charge System (VICS) Solenoid Valve Circuit Malfunction.
Possible Causes:
1. Open circuit between main relay and VICS Solenoid Valve.
2. PCM malfunction.
3. VICS Solenoid Valve malfunction.
4. Short or open circuit between VICS Solenoid Valve and PCM.

P0505 - Idle Air Control(IAC)Valve Circuit Malfunction
Possible Causes:
1. IAC valve circuit malfunction.
2. PCM malfunction.
3. Short or open between IAC valve and PCM.

P0421 - Catalyst System, Efficiency Below Threshold.
possible Causes:
1. Warm-up Three Way Catalytic (WU-TWC) converter deterioration or malfunction.
2. Exhaust system leak.
3. Loose rear HO2S.
4. Loose front HO2S.
5. Front HO2S Malfunction.

"Sounds like", from what you are describing, you have resolved any ignition system related issues. if it where my car, I would start with the IAC code...(your Idle Air Control) , Then deal with the VIC Solenoid. Once those two issues are resolved, you should be doing OK.
Good Luck & Let us know how it works out.
 
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