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Mazda 6 GH 2.5i - engine jerking after warm up

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Hello Scotty,

I was really happy with my mazda 6 until recently one nice warm summer day the engine kicked back like it stalls for a second. I was surprised but nothing else come up and it drives normally right after but I soon found out that this was just the beginnig of the uknown problem.

Since that day the kicking/stalling occured more and more frequently to the point that car is pretty much undrivable.

I took it to several mechanics, mazda dealer but no one was able to diagnose the problem. There is no trouble code in the system except showing low catylytic efficiency for some time and that oxygen sensor didn't pass the test  but no mechanic confirmed this and oxygen sensor is showing values while running though I'm not sure if they are in reasonable range (maybe issue of my cheap OBDII)

 

The problem is that engine is really kicking/jerking, like it stops for a split of a second while rpm indicator jumps to the end of 7k rpm and right back. This is happening only after engine is running for a while and is fully warmed up. In between kicking it doesn't feel like acceleration is influenced in any way. No smoke from the back, no diagnostic codes. The really weird thing to me is jumping RPM's indicator. I changed spark plugs, spark coils, I tried to disconnect the MAP, MAF, Knock, Camshaft position and O2 sensor. All pushed trouble codes but the kicking persists.

Per mechanic's check the timing chain should be OK, apperently some solenoid wasn't opening some valve which I had replaced and the issue also persists.

The car is serviced regularly I try to keep it in good condition but this problem really makes me wonder if it is worth the effort....

I will replace the camshaft and crankshaft possition sensors and clean MAP and MAF sensors but I doubt this will solve the heavy kicking/stalling. I will also check the catalytic converter for blockages but operating temperature look just fine and there is no indication of bad combustion from the mufflers. I  also notice slight change in idle, the rpm's are like changing a bit after a while but it is only slight change, nothing dramatic and the engine isn't shaking or anything. I noticed lower power on the bottom and engine stalled a few times while i was parking but it could be by exceptional outside temperature when the air is really hot and overall performance is influenced.

Otherwise car starts just fine, idle is pretty much OK, reacts to gas well, I had the throttle flap check and confirmed this runs well as well... It pulls good until the end and when it kicks during the acceleration it continues to accelerate normally. The problem is that kicking is now so often it sometimes just jerks in stead of accelerating. It's like some one hits you with baseball stick (no funny business!)

 

I'm really disappointed by "mazda's reliability" and the fact that no one around wants to touch this japanese masterpiece.

Appreciate any suggestions, couldn't find anyone so far with similar problems nor anyone who would be willing to take a proper look and diagnose all possibilities one by one.

 

 

 

 

 

Clarification: Year, mileage, engine (is it naturally aspirated or is it turbocharged 2.5L I4)?

2008 second gen. it is naturally aspirated 2.5 i4 and it has 235k Km which translates to about 145k miles. No excess oil consuption either

4 Answers
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I could be wrong but it sounds like a clogged cat causing the problem.  I would definitely look into that

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I will have the cat and the electric circuits checked next week, if the cat will look bad I will just have it removed and I hope this is the issue cause everything else seem to run just fine, no ignition issue or anything, spark plugs are new, the old ones were pretty clean, no oil or anything....  Mufflers and Y pipe are basically new (3 months) so no back pressure there...

wish me luck cause this is nightmare... no diagnostic issues, no leaks, everything seems to work just fine but car is pretty much undrivable...

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I tried to run few miles today... as soon as engine got hot the ride becomes impossible. However, as i disengaged clutch rpms becomes normal again, engine reacts to gas as usually and idle is without any problem. Bringing up rpm's on idle - absolutely no problem as well.

During the ride however the RPMs indicator is jumping and the engine light is flashing while engine is stalling for miliseconds as well as battery light is flashing, literally like engine is dead for a miliseconds.

I'm starting to think there is some electrical problem or some sensor is confused while driving. If car is not moving or clutch is disengaged everything is fine. But, I can't rly drive with clutch pedal down... 🙁 Also I'm confused why this happens only when engine is fully warmed-up Serious

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Topic starter

So I just changed crankshaft and camshaft position sensors and cleaned up MAF and MAP sensors. MAF was really ugly, covered in black s**t.

I put it all together, started and engine died few seconds after 😀

I reset the the ECU started engine again and i noticed that oxygen sensor 2 is giving completely different numbers than before. I was driving around for about 20 - 30 minutes and no kick back from the car happend, it is also pretty hot outside as when the problem started.

 

It looks like one of these sensors solve the issue but about a week ago I also drove about 100 miles with no issue and on next day the car was undrivable again.

So lets see after the weekend but for now it looks like the problem is resolved.

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