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2000 Mazda 626 Bad Knock Sensor Caused Intermittant Hard Start


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HW1000
New User

Dec 9, 2017, 10:36 PM

Post #1 of 5 (318 views)
  post locked   2000 Mazda 626 Bad Knock Sensor Caused Intermittant Hard Start  

Hello! I have a 2000 Mazda 626 LX 2.0 L. In the last month I began having intermittent hard starts (crank no start) which would occur two to three time and then it would start up. This started happening one to two times a week, and eventually my car began stalling on startup (i.e. firing right up but RPMs immediately dropped below 200). It would eventually start up after trying a few times and/or putting my foot on the accelerator. I only let that happen twice before getting it into a mechanic. I left my car at the shop for two days because they could not get it into a no-start state(no surprise). All of their other tests came back normal, as they initially thought that this was being caused by a flooded engine. But finally it would not start and threw a P0325 code, for KS. They replaced the knock sensor and so far so good.

Background on car: was a family car for previous owner, spark plugs, fuel system cleaned/serviced, and air filter replaced ~4 years ago.

I came to the forums to get opinions/ information on how a knock sensor would cause a hard start problem. As a woman, I do a lot of research when my car has problems before I go throw my money at a mechanic to fix it, so reading pretty much every post about knock sensors and how they WOULD'NT cause a hard start problem was very concerning. But at the same time, if this does fix my car (and I will update this post), I want everyone who is wary about putting down money on a KS because they think it must be another problem to know that it can cause a hard start problem.


(This post was edited by HW1000 on Dec 9, 2017, 10:40 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 10, 2017, 12:06 AM

Post #2 of 5 (276 views)
  post locked   Re: 2000 Mazda 626 Bad Knock Sensor Caused Intermittant Hard Start  

Yuk - an intermittent issue that shows itself just a couple times a week is a pest. Not so sure KS or the circuit is the cause maybe a result of the problem.
What to do if no other codes to assist? Think I'd clean throttle body real good first meaning spraying and cleaning right down intake. Not sure what you had for so called fuel system cleaned what that was maybe just a can of something in the fuel doesn't solve much never mind that was 4 years ago.


Possible can't prove it unless caught in the act is fuel pressure isn't holding up enough on the list of maybe reasons not regular enough unless witnessing it with a gauge on it at the time stinks.


It's ~18 years old at least rule out the obvious vacuum leaks the shop should have already done that may not have and all services listed are up to date both time and miles since done last.


Again, if it's going to play hide and seek like that the guessing game can get costly not sure you can help doing a couple things that are likely with this and wont know for sure unless it doesn't do it again for longer than this happens that the right thing solved it for good?


T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 10, 2017, 6:27 AM

Post #3 of 5 (266 views)
  post locked   Re: 2000 Mazda 626 Bad Knock Sensor Caused Intermittant Hard Start  

You very likely DID need a knock sensor as that is a common issue on those but I don't believe it contributed to the issue you are currently having. A bad knock sensor won't cause a "no start".



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



HW1000
New User

Dec 14, 2017, 10:38 PM

Post #4 of 5 (208 views)
  post locked   Re: 2000 Mazda 626 Bad Knock Sensor Caused Intermittant Hard Start  

It’s been a week and my car has started up every time and I drive daily. Seems to be a bit quicker on the startup, also. Still I only received answers on how a knock sensor would not have caused my starting issues but they seem to have been resolved from the replacement of the knock sensor.
Any final thoughts? Mostly just wanted some answers on the logistics of how a knock sensor can cause this, and hope this helps anyone else who is debating on fixing theirs! It was a $220 fix, mostly paid for the part with about half an hour of labor.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 15, 2017, 5:43 AM

Post #5 of 5 (188 views)
  post locked   Re: 2000 Mazda 626 Bad Knock Sensor Caused Intermittant Hard Start  

There should never be any debate on the repair. If the knock sensor is bad, replace it, regardless of what the symptoms may be or not be.

Since this issue appears to be resolved I will close this question now.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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