"shuddery" revs in neutral....

[chris_c201]

All,

When idling, if it touch the accelerator it seems a bit shuddery, and doesn't seem to drop revs instantly.... Under load, i.e. In gear it runs perfectly smooth....

Any thoughts?

[awkgah]

hi. initial step is to get a carb cleaner and give a thorough clean in both throttle body and maf sensor.

[Turbo_Steve]

I'd beg to differ there - MAFs on these are a Karmann Vortex type, so don't tend to suffer the usual issues associated with hot-wire MAFs. I'd venture to say that contaminating it with carb-cleaner isn't going to do a lot for it's longevity.


The throttlebody on VR4s doesn't tend to get that dirty either (though there is no harm in cleaning it). What can get massively gunked up is the idle control valve. The best way to clean this is to remove the throttle body completely, remove the whole assembly from the bottom of it, and clean it out thoroughly: it'll probably be full of oil and nastyness. I'm considering fitting a drain hole, blocked with a bolt, into the bottom of mine!

Whilst it's in pieces, you can also re-shape the "bung" on the end of the stepper motor, to move the idle point to a different coil.

Significantly, however, most of the VR4s that seems hesitant on throttle and wobbly at idle (mine included) have needed HT leads and plugs. It's probably the leads, but as you need to take the manifold off, you might as well do the plugs as well.

Unless you've changed the leads very recently, they'd be the first thing I'd do before looking for more issues.

[awkgah]

well there are several reason for car not running smooth some of those mentioned above. but for me I will first clean the throttle body only. it does sometimes carbon deposits makes the throttle body not to return to its normal point leaving the revs go down slowly. if that doesnt cure then yes further steps are to be taken but in a rather later stage.

[chris_c201]

Right, so plan of attack -

1 - Clean throttle body
2 - Clean stepper motor

If this doesn't solve the problem (hopefully it will as their of these cost money!) then look to the HT leads....

I done the plugs a few weeks ago, hasn't impacted the issue one way or the other..... how much are HT leads, and is generally just the leads or coil packs on the front bank as well?

Cheers for the responses,
Chris

[chris_c201]

P.s - Any tips on how to remove the throttle body to do the first two steps?

[Turbo_Steve]

Not really - you can leave the inlet manifold on.

There are two coolant lines - best thing to do is clamp them with some mole grips (i.e. you'll need two pairs). Stops it getting decanted everywhere.

Other than that, it's carefully remove the throttle cable, unplug the sensors, and unbolt, IIRC.


I very much doubt it's a coilpack - as it's wasted-spark, a failed/failing coil pack will tend to be very pronounced as you lose two cylinders!



My experience has been that it tends not to die back to idle that quickly anyway on the VR4 - not sure if other peoples experiences match this?
If the engine is cold when you try this, it will hang around at high revs anyway as the ECU behaves differently until the engine is up to temperature.

Just out of interest, how is your fuel economy?

Leads from Camskill are circa £50 IIRC.

[MarkSanne]

First things that come to mind are what's mentioned, however: if nothings comes from that: maybe check if the gearbox is (too) close to the center member which also has an engine support bushing. Mine was bent slightly bent towards the engine parts because of several hits to it by speed bumps. If tried to get it back into the correct shape a bit and also cut away a few mm around the gearbox bolts where it 'just' touched when standstill @ idle.

As said: it's probably something else and you mention neutral specifically, but you never know.

[chris_c201]

I've only had the car for a short while so can't particularly comment on MPG but out of my first full tank i was close to the 300 mark with a mix of driving so i'd say it was pretty decent.... certainly not ridiculously low....

Well, i'll clean up the ICV and report back!