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Discussion Starter · #1 ·
My car engine starts to shake whenever my radiator fans turn on. They will turn on and off while idling with my ac. Any suggestions on what might be wrong with my radiator. I am going to look at it tonight just thought I would get some opinions and suggestions of what it could be.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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My car engine starts to shake whenever my radiator fans turn on. They will turn on and off while idling with my ac. Any suggestions on what might be wrong with my radiator. I am going to look at it tonight just thought I would get some opinions and suggestions of what it could be.
Hello. If I had to guess I would say that your idle is dropping making the motor shake. The fan kicks on and draws more current. The AC compressor puts an even greater load on the motor. As a result of the greater current draw, the load on the alternator increases and the motor RPM drops. The AC will want to slow it even more. The shake is probably exacerbated by old and worn motor mounts. Here is where I would start. Make sure the air filter is clean and there are no clogs. Look for a vacuum leak. The intake accordion tube is the first likely place. Spread the pleats and make sure there are no cracks. Work you way around the various intake hoses and see that they are all intact. I would next look at battery health. Specifically look to the grounds and make sure they are clean. Clean up the terminals and the chassis and motor ground cables. The second would be the alternator. Make sure the belt is not slipping (old and stretched) and possibly putting out low voltage in general. There could also be an issue with the purge solenoid.
Poke around and tell us what you find.
Good luck.
 

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Discussion Starter · #3 ·
Thank you for the help one more question because I have been looking into things and I am wondering if the idle rpm fluctuation is due to fuel injectors would that be something I should check too.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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Thank you for the help one more question because I have been looking into things and I am wondering if the idle rpm fluctuation is due to fuel injectors would that be something I should check too.
I would only do that after the more common issues are checked.

Remember:
"Four hooves with a saddle, what is it?"
  1. Horse
  2. Donkey
  3. Camel
  4. Zebra
  5. Giraffe

In the US, the above order is most likely.

The list I posted before is in the order of how I would proceed. Others may have different opinions.(y)
 

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To add to Dr's list - check your PCV Valve/Hose. The OEM hose is well-known to crack/crink and cause rough idle issues. $10 and about 20 minutes later you can have a new valve and hose put in.

And check/clean your MAF
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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4,403 Posts
To add to Dr's list - check your PCV Valve/Hose. The OEM hose is well-known to crack/crink and cause rough idle issues. $10 and about 20 minutes later you can have a new valve and hose put in.

And check/clean your MAF
This is a good suggestion. In the v6 the later models (after 2004) came with an upgraded hose and valve that resists collapse.
Here is the v6 thread but there may be an equivalent for the 4-cyl (?).
6s (V6) PCV Valve Failure, Excessive Oil Consumpti
When this happens the motor is frequently idling just a little bit lower than normal and when the fans kick on it is just a bit more than can be overcome and as a result it shakes. You could test to see if it is load related, by turning on electrical components when the fans are not on, but the engine is warm, and checking for shake.
 

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2004 6 i
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Discussion Starter · #7 ·
I would only do that after the more common issues are checked.

Remember:
"Four hooves with a saddle, what is it?"
  1. Horse
  2. Donkey
  3. Camel
  4. Zebra
  5. Giraffe

In the US, the above order is most likely.

The list I posted before is in the order of how I would proceed. Others may have different opinions.(y)
Ok thank you so much
 

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Watch your tachometer when this happens and see if it momentarily dips. Regarding vacuum leak or PCV leak, this would happen randomly without regard to what your radiator fans or AC are doing. My guess, if your idle is dipping whenever the AC compressor kicks on (which is what I bet is happening) is that you might have a bad IAC valve (idle air control). The purpose of this valve is to slightly bump the engine speed up whenever the AC compressor kicks on. This prevents the added load of the compressor from lowering your idle causing a rough idle or even a stall. Contrary to the advice above the alternator load on the engine is relatively slight and should not cause a low idle, unless your electrical system is so garbage that even a radiator fan kicking in causes a big voltage drop that the system is unable to keep up with, but again I doubt seriously that this, or any of the other suggestion listed above are actually your problem.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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The Mazda 6 does not use an Idle Air Control Valve (IAC), it has been superseded by an electronically controlled throttle body. The Idle-up (if equipped) is controlled by the PCM and generally bumps the RPM to 650-750 for electrical load, 700-800 RPM with the AC on and 650-750 RPM for Power Steering. Your Idle should be between 650-750RPM when warm in neutral/park with no electrical load, no AC and not steering.
 
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