igropemotoko

(Found leading plug with cracked ceramic. Arc jumping. Replaced plug. Problem solved.)

Almost out of nowhere I began to have a problem when starting the car. It starts up almost instantly every single time, hot or cold and anywhere in between but after a cold start the engine misfires almost comically. The CEL flashes (The only code I have is a Misfire code) and the car runs like crap for about 10 to 45 seconds then suddenly -boom- it runs perfectly smooth. After a hot/warm start, there is absolutely no issue.

I have noticed perhaps the past two or three times that the misfire seemed to stop at the exact moment the Air Injection pump cut off. I don't know if there is a correlation here but that pump only pushes air into the exhaust system, correct? So the only effect I can see it having is on the upstream O2 sensor. Still, I would imagine that during startup, the engine probably runs on a predetermined map and since the O2 sensor isn't warm, it isn't reading data from it anyway.

Some Facebook (Risky Rotors) friends have suggested a poor contact somewhere that works fine from heat expansion after the warm up and of course suggested coils and plugs but I have already replaced them less than 1K miles ago.

Something to note, the car runs perfectly at the top of the rev range and feels like an absolute rocket but below 4K there feels like a bit of a power loss almost as if the timing is not correct. Also, when at super low engine speeds as you let off the clutch there is sometimes a semi-stall hiccup that never used to happen. And it also seems to me the idle tone at the exhaust seems more airy and less crisp. This made me consider the ESS. I am going to try to clean it today and see if there is any change.

I considered compression too but almost everyone says the same thing, I would almost certainly have some sort of slow start or hot start issues. But by the second rotation it grabs and starts every time.

Anyone else with some ideas?

-2004 Base - 138K on car
-37K on Mazda Reman Engine
-Cold Start Misfire
-Lack Of Low End Power under 4K (SSV is working)
-Full top-end power / No misfires under power
-Plugs, Coils, Ign Wires replaced 1K
-Have tried different (and cleaned) MAFs

igropemotoko

Still having this problem. I noted that last night after sitting for hours, the car started up completely normally. I have done some more searching but haven't really found anyone with a problem quite like this.

I pulled the plugs and, as expected, they seemed fine. I cleaned them and checked the gaps. I've cleaned connections with the ignition system, MAF, pressure, TB, solenoids, etc. I can also detect no vacuum leaks.

Front 247 RPM (KPA)
811
830
818

Rear 249 RPM (KPA)
803
811
798


Seems good. Anyone with any ideas?

igropemotoko

Finally! I may have found a thread with the answer. Possible coolant seal! I guess we will drive it until it dies then do it all over again if I can find no other cause. =]

G_ man

iTrader: (2)

If your getting white smoke out the tail pipe then yes you could have a coolant leak.
Just get a coolant pressure tester and check to make sure.
Also check the cat to see if it's plugged.

igropemotoko

I can't think of any other explanation. It's a shame since the compression is so good! I think because it became my daily ride, my warm up times suffered.

I will try to do a pressure test this week. I have a catless mid pipe I can put on the car once inspected. Who knows? Maybe it could be a cat issue.

OnCam

Interested to see how you get on i think mine may have done a similar thing which i have noticed only twice before.. mine when started cold would lightly just pop every 3 or 5 seconds or so on idle but then on two occasions it went into a continuous popping/stuttering for 3-5 seconds. no CEL flashes.

I was worried so went and started it when the car was completely cold the other night an idled for 5+ mins with no stuttering. i have also noticed a very tiny single drip of coolant on the floor like right under the car near the firewall about 3 times, but nothing of late. done 60,000kms (not miles)

igropemotoko

We shall see. I am going to do a coolant system pressure check sometime this week. Yours sounds far less serious like plugs/coils perhaps. Maybe a leaking/dirty MAF or dirty ESS. So many things can cause it. It's just so strange mine is giving me this slight hint of missed power at the bottom end. I may have more than one problem going on but right now this start up issue is taking priority.

OnCam

did you manage to get the coolant pressure check done? keen to know how your progressing

Harlan

iTrader: (3)

Or you could always check the old school way.

igropemotoko

No coolant leak anywhere. Pressure is holding fine. I had someone else start up the car while I stood behind the car and holy hell, it's like raw gasoline coming out of the exhaust. No steam or burning coolant smell. It seems to do this when the ambient temp is high. When it is cooler outside, the start up is smoother. Hot starts are still perfect.

Perhaps a leaking injector?

Dripping fuel while off and having some issues with fuel delivery at low RPM? Again, above about 4,500 revs power seems perfect but when hotter ambient temps exist the low RPM power is crap. The commanded AFR vs. the measured AFR seems a bit leaner so it could be a bit more fuel than it wants? Then when the staging of other injectors sets in, the effect is diminished? Any thoughts?

Only CEL that keeps coming is Cylinder 1 Misfire.

igropemotoko

And following that logic, it could likely be a primary injector, right?

I don't know. I am running out of ideas.

oxygen

i am facing the same problem 2weeks now..
i own a challenge 2007 with 78k.
with black halo racing ignition upgrade.kn panel filtre and a hjs 200cps catalyst..
plugs replaced over a year ago and checked out ok and lately changed to idemitsu oils.
do you have any solution by now?
i suspect fuel pump..

Harlan

iTrader: (3)

I'd spin the engine through cold (just for a moment) without starting (throttle to the floor) then pull the plugs with and see if they are wet with gas or oil. If one pair of plugs are wet then we have a smoking gun.

igropemotoko

I'll give that a try Harlan. I have attempted to allow the car to "deflood" with the pedal to the floor to see if it started any better but it's been mixed so I don't know if it helps. I will try to do that and check the plugs after the fact.


Oxygen, fuel pump might be an issue but to me, my exhaust fumes are LOADED with the smell of raw fuel. So I feel like it's too much for some reason, or just not burning it for some reason.

I should post back within a day or two. Been working on the car all weekend. Doing new pads and rotors today.

oxygen

i have also the same problem with the smell of fuel only at first start..
i don`t always get a missfire though at cold start..

i am trying to figure out what might be failing during "cold"engine start up that stops after 5' idle.
After this rough idle everything is back to normal with no power loss or any other issues!

i use an obd2 b/t adapter with my phone to check parameters..should i focus on any specific one?
rough idle stops after coolant raising to 80c..

igropemotoko

Well, I did as Harlan suggested. Plugs were dry... BUT WAIT! I am 99% sure I have found the damn problem and this just goes to show with all the known, common problems these cars have you sometimes have to go back to good, old, simple common sense that we too often overlook.

Yes, I smelled way too much fuel.

Why? Because this.



This is the front leading plug. I have taken it out twice before and remember there are only 1.2K miles on these plugs and coils and I checked frequently when this problem first started. I had ruled out the plugs but it seems that right from day one, this plug had cracked ceramic and I am pretty sure the arc was jumping. After some heat, things swell and perhaps close the gap? I don't know. When I pulled the plug to see if it was wet, it came out fine. As I was holding it the ceramic fell apart in my hands! Either way the end of the plug now looked like garbage. I cleaned the trailing in the front as it looked a bit rough too but being so new I wasn't spending $20 on that one too. I bought a new leading, popped it in and I am waiting for everything to cool. If I get a few perfect starts, this will certainly have been the problem.

I still find it amazing I got NO high RPM misfires.

Fingers crossed.

speedracer2169

I had the same problem that you had. Ended up being a bad battery. Replaced the battery and starts up fine every time

igropemotoko

The cracked plug was indeed the problem. Car starts perfectly now. Still having a low RPM power slump with now CEL. More work for the weekend I guess.

Jeff adams

First post. Lame. Anyway I am also having low end rpm low power or misfiring. No white smoke tho. I changed coils to the bhr and cleaned maf. Next s plugs and leads. Keeping fingers crossed..