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post #1 of 7 (permalink) Old 09-12-2018, 07:15 PM Thread Starter
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Failing VVT?

I replaced the timing chain, all gearing with it including the VVT actuator about 5 months ago.

Car ran perfect for about 3 months, then i put it up for sale. On about the 4th person test driving, i started to notice loss of power between about 1800 and 2700 RPM (estimated). I replaced spark plugs, and coil packs, as i have had issues with those parts in the past with no effect. I took it into mazda, and they said they are seeing misfire counts on all 4 cylinders. The problem is inconsistent. Sometimes it doesn't happen at all, sometimes it lags quick and comes back (like when traction control takes over). Sometimes it bogs and doesnt recover until i push in the clutch rev the engine out and re apply throttle under load. Mazda also said all sensors seem to be functioning normally. I also checked the compression and i get 175 PSI on all 4 cylinders.

Has anyone had an issue like this? I am thinking the VVT actuator I installed may have gone bad? I know there was the TSB on VVT. Did anyone have this issue? what were the symptoms?

I also think i may have a small exhaust leak in the exhaust manifold. Small enough you cant hear it. Could this also be the cause?

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Bmxer4l1fe

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post #2 of 7 (permalink) Old 09-12-2018, 07:59 PM
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Quote:
Originally Posted by bmxer4life View Post
I replaced the timing chain, all gearing with it including the VVT actuator about 5 months ago.

Car ran perfect for about 3 months, then i put it up for sale. On about the 4th person test driving, i started to notice loss of power between about 1800 and 2700 RPM (estimated). I replaced spark plugs, and coil packs, as i have had issues with those parts in the past with no effect. I took it into mazda, and they said they are seeing misfire counts on all 4 cylinders. The problem is inconsistent. Sometimes it doesn't happen at all, sometimes it lags quick and comes back (like when traction control takes over). Sometimes it bogs and doesnt recover until i push in the clutch rev the engine out and re apply throttle under load. Mazda also said all sensors seem to be functioning normally. I also checked the compression and i get 175 PSI on all 4 cylinders.

Has anyone had an issue like this? I am thinking the VVT actuator I installed may have gone bad? I know there was the TSB on VVT. Did anyone have this issue? what were the symptoms?

I also think i may have a small exhaust leak in the exhaust manifold. Small enough you cant hear it. Could this also be the cause?

Thanks,

Bmxer4l1fe
Which engine are we talking about?

What codes do you have?

Mileage?

My first guess would be fuel injectors. But I need more information to properly diagnose.

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post #3 of 7 (permalink) Old 09-12-2018, 09:30 PM
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Quote:
Originally Posted by Get Inline View Post
Which engine are we talking about?

What codes do you have?

Mileage?

My first guess would be fuel injectors. But I need more information to properly diagnose.

That is why he posted in the Speed6 section, pretty self explanatory.

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post #4 of 7 (permalink) Old 09-13-2018, 03:52 AM Thread Starter
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its the MZR 2.3L mazdaspeed engine. 125k miles, no codes.

wouldn't bad fuel injectors cause a problem at high RPM / Boost? car runs great above 3500 RPM. 12-15 psi of boost, and pulls like new all the way to redline.

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post #5 of 7 (permalink) Old 09-13-2018, 09:03 AM
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If the actuator is stuck it could do as you are describing. Hopefully someone will chime in with the diagnostic flow chart for this, I'm not sure where to point.

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post #6 of 7 (permalink) Old 09-13-2018, 03:02 PM Thread Starter
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Originally Posted by b1lk1 View Post
If the actuator is stuck it could do as you are describing. Hopefully someone will chime in with the diagnostic flow chart for this, I'm not sure where to point.
This is really all i was looking for. When i replaced the vvt/ chain, i thought my engine was hosed. I was thinking bent valves etc because there is so much conflicting info on the internet on if this engine is an interference engine or not. Due to this, i bought the cheapest kit i could get(which in hindsight was probably a bad idea) assuming it would not run anyways after i replaced it. I was super surprised when it started up, blew a small cloud of smoke and was back to life 100%..

I will see if i can get mazda to get me the raw data logs, but i doubt it. my dealership is not the nicest of people.

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post #7 of 7 (permalink) Old Yesterday, 09:31 AM
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I don't know about it being an interference engine or not, but when my VVT broke all 16 valves were bent, so yeah...I don't think it's your VVT, I have been driving mine with the VVT completely disabled (blocked) and it runs basically the same, except it takes more time to rev from 2.000RPM to 3.000RPM. Seems more like electrical or injector related to me. Failing coil pack maybe?
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