P0300 and rough idle

N

nktm

:
Mazda Protege ES 2002 Sunlight Silver
ok, so I have a problem, not sure how big or where to start, but when ever I start my car I have a really rough idle, and sometimes will even die. However, IF it makes it through the rough idle, it will go to a normal idle (almost like it needs to warm up). After that the car runs PERFECT, and I don't see any problems (no leaks or holes from what I can tell)... Soemtimes I will get the CEL, and when I check it it shows up at P0300 "Multiple random misfire". So far I changed the ignition coils and wires - not cheap =( - and it seemed like it solved it for a bit, but problem came back like a day later. My car is at 87,000 miles, it has new sparkplugs as well and I checked the spark plugs too and they look brand new still.... Where else can I look??
Someone said a leak in the head gasket, but if that were true, I wouldn't be able to run the car at all right? I'm gonna do a cpompression test, and I'm pretty sure it's going to be ok seeing as I did one like 1 month ago and it was fine.
I have a 02 mazda protege, 2.0L
Thanks for your help in advanced!
 
Well when my protege started to idle very rough it would sometimes die on me when im at a stoplight ! The problem was there was a small rip in the intake hose (vacuum hose), so got that replaced and fixed the problem :)

Even the smallest rip/tear in the intake hosing (vacuum hosing) can make it idle rough so make sure to check..
 
Last edited:
Thanks SeaN69 for the reply, I actually have a Injen CAI and I checked and nothing is leaking or anything. If there was, then whenever I idle, shouldn't it be rough? My problem is ONLY idling right at start up. After it warms up so to speak, the idle is like perfect.

I checked the compression, and the cylinders are fine, I also checked the throttle and it looks very clean.

What else can it be?
 
I'm almost 100% sure it's the EGR valve stuck OPEN. That happen to my P5 last month, just replace or clean it. There's a How-to on the forum. Good Luck!!


nktm said:
Thanks SeaN69 for the reply, I actually have a Injen CAI and I checked and nothing is leaking or anything. If there was, then whenever I idle, shouldn't it be rough? My problem is ONLY idling right at start up. After it warms up so to speak, the idle is like perfect.

I checked the compression, and the cylinders are fine, I also checked the throttle and it looks very clean.

What else can it be?
Click to expand...
 
yea, after sooooo much searching through the forums, I think it is the EGR valvue too... So I guess I'll take it apart and clean it...

ScratchNSniff, interested, but why are they so cheap?? $15 shipped sounds like they are practically free... haha sry for being so skeptic....u can never be to cautious about internet deals. =)
 
haha ohhh I c. Well for now I am going to take it apart and clean it. I'll let you know if I want it later. Thanks tho!
 
ok guys, I took out the EGR valve, cleaned it like none other, and put everything back but I still get a rough start/idle, but after it a few seconds, it idles perfect.... The weird thing is I haven't gotten the P0300 CEL so far...so maybe we are on the right track. What could be causing the rough idle at only the beginning?
 
Im having a similar problem with mine, when it starts its like normal after getting warmed up its ok for a few seconds then it starts to boggle like it wants to die it hasent yet because the light changes and i take off. when it drives its fine only when idling I did the same swapped out plugs and wires and it just got worse. any other ideas?
 
well my problem was fixed I had a hole in a line a buddy found it and fixed it, hope you get yours fixed buddy
 
hmm I have a Injen CAI so I'll have to check the hoses and such, but I don't think i saw any holes before... I just got the CEL back today and still the code P0300! >.<
 
i would also check your vacuum lines, one right above the egr valve seems to pop loose alot on these cars, it will cause rough idle and throw that check engine light. might have to replace egr valve and i would try to sea foam it as well that would tell you if there are any leaks at all.
 
I have the same problem with a lean idle code 2187 and 2177 with the misfires. I have a Injen CAI but i don't think thats the problem. The car ran strong with about 10,000 plus miles with all my mods. All of a sudden one day bammm code after code. I've change all hoses and couplings, changed maf, and top o2 sensor, cleaned egr, check valve replaced, throttle body, upgrade fuel pump. Tonight i'm gonna test the plugs and coil packs and shoot a special mazda cleaner through the motor cleaning the heads, block, valves and cylnders. $50 dollars a can ridiculous..... i've spent alot money trying to fix the problem. When I figure things out I'll post...
 
Please log in or register to reply here.

Similar threads

S
2002 Protege Occasional Rough Idle
Replies
7
Views
2K
salguod
S
E
2000 Protege 1.6L Manual - Rough Idle and no power until reaches 170F
Replies
3
Views
3K
AzteCypher
AzteCypher
A
  • Question
Random Repeating Engine Misfires (2002 Mazda Protege)
Replies
1
Views
447
njaremka
N

Latest posts

Back