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Engine Specific Info and Questions => IDI Engine => Topic started by: 92EcoDiesel Jetta on October 17, 2009, 07:59:01 pm

Title: engine idle RPM
Post by: 92EcoDiesel Jetta on October 17, 2009, 07:59:01 pm
I think spec is 950 RPM? I have a tach in the cluster which is accurate enough (calibrated with a 3450 RPM AC motor). At 1000 RPM, the idle is not smooth at all and just does not sound right. If I set it to 1100-1200 RPM, it is much smoother and sounds much better. Do you see any issues with a higher idle? What idle RPM is your engine set to?
Title: Re: engine idle RPM
Post by: truckinwagen on October 17, 2009, 08:01:33 pm
the higher idle will use more fuel and make the car run hotter when sitting at a light.
not huge issues, but lowering the idle is still a good idea.

start by checking your motor mounts, if they are bad they can cause vibration at idle.
Title: Re: engine idle RPM
Post by: 92EcoDiesel Jetta on October 17, 2009, 08:39:16 pm
Quote from: truckinwagen on October 17, 2009, 08:01:33 pm
the higher idle will use more fuel and make the car run hotter when sitting at a light.
not huge issues, but lowering the idle is still a good idea.

start by checking your motor mounts, if they are bad they can cause vibration at idle.

More fuel at idle yes. But hotter at a light? There's no load at idle so a hot idle should be no issue?
Title: Re: engine idle RPM
Post by: truckinwagen on October 17, 2009, 08:45:03 pm
more fuel means more heat.
at a light you have no air passing through the radiator(until the fan turns on)

I had my idle jacked up quite a bit to mitigate really bad motor mounts and found that the temp would rise to the point of needing the fan much more quickly than it did with the lower idle.

not a big deal like I said, but it is there
Title: Re: engine idle RPM
Post by: neimis on October 17, 2009, 11:08:19 pm
Just changed my rear (passenger) side motor mount 1 hour ago. It was the original mount ('92 Passat TD). My God, what a difference. The car is like new! Vibrations gone, shifting smooth, idle is nice. Car even seems to have more power! (I know it's just my imagination). I had previously changed the front mount, didn't make any difference. Now I will complete the set by changing out the transmission mount too.

If you don't know how old your mounts are, it's certainly worth a try.
Title: Re: engine idle RPM
Post by: burn_your_money on October 18, 2009, 07:10:51 am
My car idles at 1000. Anything lower and it feels and sounds like it's going to rattle to death. I think that I have an injector issue, but that will be addressed later.
Title: Re: engine idle RPM
Post by: Jettage1 on October 18, 2009, 01:38:50 pm
Quote from: libbybapa on October 18, 2009, 08:14:28 am
Shame on you Tyler... 

snort / guffaw!  ;D
Title: Re: engine idle RPM
Post by: Vincent Waldon on October 18, 2009, 02:16:02 pm
The cobbler's kids always have the worst shoes...
Title: Re: engine idle RPM
Post by: burn_your_money on October 18, 2009, 03:47:45 pm
 :-[ I don't even know what to say...

Another potential cause of a rough idle could be uneven compression. You should check compression with the engine cold and with the engine at temperature.
Title: Re: engine idle RPM
Post by: veedubcanuck on October 18, 2009, 03:57:36 pm
Quote from: burn_your_money on October 18, 2009, 03:47:45 pm
:-[ I don't even know what to say...

Another potential cause of a rough idle could be uneven compression. You should check compression with the engine cold and with the engine at temperature.

 Question here.... What temp does the engine need to be when checking the compression "hot"? By the time you pull the injectors and lines out the engine is cooled off considerably...