Engine "shakes" when thermo fan kicks in

[webbiegareth]

Hi all,
Sorry for all the different threads - I figured it's better to make one for each of my larger issues.

In our AU Series 1 (i6), it's got a slight random shake at idle, but this problem is slightly different. When the thermo fans kick in, you can "feel" the engine engine shake or possibly lose power (?) for a second and then it's fine again. It's definitely noticeable when the car is sitting there idling and the fans turn on.

Now the AU has electric thermo fans, so I wouldn't have expected to feel anything at all with the engine when they kick in (apart from hearing the fan noise).

Does anyone else experience this? Is it normal? Or is there a problem somewhere? (i.e. alternator not supplying enough juice, bad battery etc)

[FreddyDUZ747]

Its the mass voltage being taken by the thermos at once doing it,have you checked the condition of battery and alt?

Every car does it to a degree but some are worse usually due to some areas not 100%.Usually the more accessories on at the time will make the drop a little more noticeable also.

[webbiegareth]

It almost has an "uh oh the car is going to stall" feel to it sometimes.... but it never does. The battery condition is unkown (since we've only had the car 6 months), however it had a high pressure power steering hose leak so no doubt there's PS fluid on the alternator.

I'm having new suspension fitted next week, I'll get the mechanic to test both the battery and alternator in that case... damn.

[rowan194]

The thermo fans place a high electrical load on the electrical system and alternator which in turn places a higher mechanical load on the engine. If it's right on the line of stalling then that may be enough to drag it down momentarily.

It may be as simple as needing an ECU retrain to re-learn the idle speed. Is it worse with the rear demister on? Does the A/C clutch kicking in when in drive+idle also cause the shuddering?

Basically you pull the ECU fuse for a minute, or disconnect the battery for 30 mins (warning: you will need your radio security code if you d/c the battery) then after reconnecting and starting the engine do 2 mins of each: park, no electrical load; park, high electrical load (A/C, headlights, demister on); drive, no electrical load; drive, high electrical load. It's the latter one that is the important bit as that is what may be causing your shudders. HTH.

[_Ben]

Originally Posted by webbiegareth

It almost has an "uh oh the car is going to stall" feel to however it had a high pressure power steering hose leak so no doubt there's PS fluid on the alternator.

Did you replace that? If so what was the cost? Mine's leaking too :(

[Mr Hardware]

what are your revs before and not-immediately after?
also clean your ISC.

[GK]

Originally Posted by Mr Hardware

what are your revs before and not-immediately after?
also clean your ISC.

Good advice and easy to do.

Cleaning ISC/IAC Valve
http://www.fordforums.com.au/showpos...9&postcount=43

Cheers,

GK