Misfire and strange electrical problems - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum
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post #1 of 7 (permalink) Old 07-07-2019, 09:28 AM Thread Starter
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Misfire and strange electrical problems

I just picked up a 2004 Manual trans wagon with 155k on it. The engine has at least one cylinder that isn't firing and some strange electrical problems also.

The previous owner said he was getting a code for a misfire on cylinder one. He reset the code before I saw the car and amazingly the CEL has not come back on again. First thing I did was reseal the valve covers, replace the spark plugs and put six new coils on it. The PO attempted some repairs but was not that mechanically inclined and I found a host of other issues at the same time- MAF screws stripped and MAF out 1/4" on one side, EGR valve not tightened to manifold. There was also a wire that I'm not sure what it does that was on the back of the engine on the black plastic piece with a few other connectors that was unplugged. It was a grey connector with a single wire in it.

It runs better for sure now but still has a noticeable cylinder or more not firing and lack of power. I then did a compression check and I'm getting 183-193psi. Which IMO is very healthy, especially for a motor with this many miles. I'm going to flow test the injectors this afternoon.

Now for the strange electrical issue. This started after I did ignition work. The tach and speedo will intermittently drop to zero and the TCS light will come on. Also at idle the oil light barely flickers. Oil level is good and I don't think it is low oil pressure since turning the steering wheel strangely makes the light come on more solidly. There's no drop in idle speed when I turn the wheel. This never happened before the ignition repair.

Is there any known trouble spot I should be checking that causes these issues?
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post #2 of 7 (permalink) Old 07-07-2019, 12:40 PM
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Quote:
Originally Posted by banzairx7 View Post
I just picked up a 2004 Manual trans wagon with 155k on it. The engine has at least one cylinder that isn't firing and some strange electrical problems also.

The previous owner said he was getting a code for a misfire on cylinder one. He reset the code before I saw the car and amazingly the CEL has not come back on again. First thing I did was reseal the valve covers, replace the spark plugs and put six new coils on it. The PO attempted some repairs but was not that mechanically inclined and I found a host of other issues at the same time- MAF screws stripped and MAF out 1/4" on one side, EGR valve not tightened to manifold. There was also a wire that I'm not sure what it does that was on the back of the engine on the black plastic piece with a few other connectors that was unplugged. It was a grey connector with a single wire in it.

It runs better for sure now but still has a noticeable cylinder or more not firing and lack of power. I then did a compression check and I'm getting 183-193psi. Which IMO is very healthy, especially for a motor with this many miles. I'm going to flow test the injectors this afternoon.

Now for the strange electrical issue. This started after I did ignition work. The tach and speedo will intermittently drop to zero and the TCS light will come on. Also at idle the oil light barely flickers. Oil level is good and I don't think it is low oil pressure since turning the steering wheel strangely makes the light come on more solidly. There's no drop in idle speed when I turn the wheel. This never happened before the ignition repair.

Is there any known trouble spot I should be checking that causes these issues?

Welcome to the forum and congratulations on the wagon purchase. There are quite a few long-top owners here and many willing to help out.


I have had issues with a misfire in the past and it lead to some other repairs including manifold replacement.


I suppose it could indeed me an electrical problem but it could also be a problem on the other end. My misfire was prolonged enough to super heat the catalyst and cause it to disintegrate. The disintegrated upstream catalyst material blew downstream and clogged the secondary catalyst causing a massive amount of back-pressure and loss of power. There was also what felt enough like a mixed cylinder misfire that I bought new coils and plugs thinking they were faulty.
Here is my parts list and link to the original thread.
https://forum.mazda6club.com/members...l#vmessage9866
The electrical issue you describe could be contributing to your issues as well. People have talked about ABS sensors and Throttle bodies causing similar dash light issues. I think the place I would start is the obvious wires you mention that are at the back of the motor. If you could get some pictures that would really help out. The only grey connectors I can think about back there are O2 sensor related. While the misfire sensor on this car is terrible at actually reporting a misfire I feel the O2 sensors are triggered rather quickly when at fault and would imagine it to appear if disconnected.

You could hear this when you got under the car a shook the exhaust back and forth.




As for the oil light flicker, I would bet the sender is faulty. it is flickering as the RPM drops. When you turn the wheel it loads the power steering and slightly slows the engine causing it to flicker more. This is an easy fix (unless it's stripped by the previous owner, like mine)


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Mozz-D
2004 6s Wagon 3.0, 5-speed ATX
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post #3 of 7 (permalink) Old 07-07-2019, 05:33 PM Thread Starter
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I couldn't post a link to the pictures so here they are attached
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post #4 of 7 (permalink) Old 07-08-2019, 06:14 PM Thread Starter
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I found the misfire problem. Injector for cylinder #1 was DOA. First time in 20+ years of playing with cars I've had one fail. Have a new set of injectors on their way.

I may have figured out the dash problem too. My scanner has been acting strangley- not connecting to car or phone or both. I got some canbus errors from another reader and interneted those. It looks like other people have had strange issues with a dodgy scanner hooked up. Next drive I'll run with no scanner and see if all is well.
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post #5 of 7 (permalink) Old 07-09-2019, 08:20 AM
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Quote:
Originally Posted by banzairx7 View Post
I found the misfire problem. Injector for cylinder #1 was DOA. First time in 20+ years of playing with cars I've had one fail. Have a new set of injectors on their way.

I may have figured out the dash problem too. My scanner has been acting strangley- not connecting to car or phone or both. I got some canbus errors from another reader and interneted those. It looks like other people have had strange issues with a dodgy scanner hooked up. Next drive I'll run with no scanner and see if all is well.
I tried running a live scan while driving 1 time in my 03 and it didn't take well to it. It bucked, lights went all crazy. It didn't mind it while parked and idling but once on the road, it was a whole different story.

I had an injector issue last year that had me so bummed out I about wanted to give up on my build and move to a different platform lol. Needless to say I stuck it out. I had a misfire, replaced coils and plugs and the misfire stayed. Took the plugs back out and the #3 plug was still dry and looking brand new. No gas smell at all on it. A set of refurbished injectors later and almost 5000 miles, no issues at all.

Nice job on finding a bad injector. It wasn't that bad of a job to do. It took me longer than it should have because I was scrubbing 15 years of grime from my parts before putting them back. I will say to leave the main fuel line connected to the rail when it comes time and just flop the whole thing over to the drivers side. It saves a little bit of time and frustration not having to disconnect the line from the rail.

Ray.
2003 6s
Brakemotive Drilled and slotted rotors, Modified eBay CAI, EGR reroute and optimized, TB coolant delete, Brake light mod, AWR Racing Lower dog bone, AWR Right engine mount, BIG 5 upgrade, Battery Relocated, Custom Busbars, Optima Red top, 2 12" Planet Audio BBD12, Rockville Audio 1400w 4chan amp, Rockville Audio 8000w sub amp, RX 8 seats, Custom LED side markers, Lower rear bumper lights, Transmission cooler, Derale Performance transmission filter kit, and lots more to come!!!

Last edited by DJ Raydiate; 07-09-2019 at 08:22 AM.
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post #6 of 7 (permalink) Old 07-11-2019, 10:44 PM
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Welcome to the club. Hopefully, you have found all the problems.


But in case. I was starting to have intermittent electrical problems this spring on my 2015 Mazda 6 that I bought in August 2014. If it sat for a couple of days, the car doors would automatically lock and would not recognize the fob. After opening the car with the emergency key, the workaround was to cycle the door locks closed and then open and the fob would then be recognized. Twice on startup, I got a misfire on number 3 cylinder. The car ran fine after startup (which I assume was because the alternator took over for powering the car). In addition, the dash board warning lights would sometimes act strange by randomly flashing on and off.



After searching the internet, I came across a suggestion from Scotty Kilmer that with today's computer systems in modern cars, a strong battery was required for a modern car's electronics. Battery was approaching five years old and living in Colorado with the cold winters and hot summers is not conducive to a battery's life. After checking it with my multi-meter and finding that the voltage under no load was good, I went over to Harbor Freight and picked up one of their $20 battery load checkers (I recommend one for those DIYers out there). It turned out the battery under load was borderline, barely met minimum. I replaced the battery with a new one and cleared the codes. Since I had disconnected the battery, it took about two driving cycles to 'reprogram' the computer. It's been about 2 months now and the car starts and runs fine.


So. If you have weird electrical problems, first load check and replace the battery if it is starting to get weak. Modern car electronics depend upon it.
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post #7 of 7 (permalink) Old 07-15-2019, 08:21 AM Thread Starter
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The oil light blinking turned out to be a bad pressure switch. That was also the source of one of the many oil leaks I've been hunting down.
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