Light Throttle Stutter

[PetrolHeadPete]

Anyone else have a slight stutter at light/balanced throttle ? Feels like a misfire but doesnt sound like it from exhaust note. Happens everywhere from 1000 to 4000+ revs. Apply a bit more juice and off she goes like a rat up a drainpipe! Have got new plugs, leads, air filter etc. Perhaps its just normal, with mapping only putting in lean fuel mix ? Have checked throttle bodies for play and wear and they look very good.

Ideas welcomed
ps: coil pack is original (its an '02 plate MK1)

[Whitey]

HT leads when I had the same symptoms.

[shep1001]

Sounds the same problem had with the Tam. second new set HT leads fixed it. Mine used to backfire too if you revved it whilst stationary (fully warmed up mind). About £45 for the leads and fitting/set up another £50-60 or so

Shep

Edited by shep1001 on Wednesday 18th March 00:30

[RM75]

Sounds similar to what happens to mine. It was suggested it that it could be the throttle bodies being worn - the key fact being that it only happens on light throttle. Here's my thread...

http://www.petrolheads.co.uk/gassing/topic.asp?t=6...

[Chequred Demon]

When my leads degraded it manifested itself as a low speed stutter and in addition at maximum throttle it was like the rev-limiter coming in early around 6000rpm.

If the spark is not sufficient then the cylinder(s) will not combust under a variety of throttle positions I would suppose?

[PetrolHeadPete]

OK, good suggestions. Its odd that some folks have needed a couple of sets of plug leads to get success. This kind of suggests the leads are OK but the fitting a routing of them is critical...I'd have though faulty *new* leads per-se was unlikely...jusy my opinion. I might try making them "untidy" and leaving off the top plug cover to see what happens.

It really seems like a weak spark could be to blame, that gets covered up with a bit more throttle.
And I too have a 6K misfire like the rev limiter...it all gets a bit frantic at 6K so dont have much time to analyse...the scenery goes past WAY to quickly at high revs...needs complete concentration.

Has anyone found any benefit from swapping coil pack ?

[Chim326]

Mine started intermittenly misfiring when hard on the gas and also on decel would backfire through the throttle bodies, checked out the leads with a multi meter and they also looked physically in good condition so went for the coil pack replacement first, did'nt make any differance. bought a set of 8mm magnecors and when fitting put spacers between the cyl head and plug cover and sealed it with industrial silicon sealer. Never had a problem since!
Just something to check as someone told me of a similar problem: make sure there are no splits or leaks in the vaccum pipes that run along the bottom of the throttle bodies as light/heavy misfire will occur depending on size of leak?
Good Luck,
Steve

[Whitey]

When I had worn throttle bodies the fault would only appear when on a steady throttle at a constant speed, it was almost like driving into a strong headwind, just very slightly affecting the throttle position, not as bad as a stutter or misfire.

[Tuscanuwe]

"And I too have a 6K misfire like the rev limiter"

My Tuscan Mk1 2000, had same, only solved problem with modified chip from
Dome!
It was not leads, coil,sparks or rev transmitter, changed all twice with no results.
Took me a long time to find this prob.

Uwe

[tu51john]

Hi- I have exactly this problem. Mines a 2001 mk1. I have thefull history as I only bought it last summer. And there is a history of hesitation back to the beginning. The last owner had new leads and plugs fitted at Leven just before I bought it and it was fine until I brought it out post winter a few weeks ago.

Now it seems slightly hesitant at low revs - probably worst between 1800 to 3k. Then it goes away. At 70 there's nothing and at 30 round town in 5th nothing either...... I thought it was me at first.

It isnt a definite misfire. It feels like an intermittant electrical miss or slight fuel starvation. Its more of an irritation.

I have carbon co cans fitted so it chatters away all the time but its definately not smooth at the moment.

If you get success can you let me know. Mines going into HHC for a 12k service in 2 weeks time so I will update when they have had a look.

regards
John

[Whitey]

I replace my HT leads at every service for the simple reason, if I don't these symptoms eventually appear. The heat in the engine bay degrades the leads, and they are cheap to replace.

[TuscSam]

I have a similar problem, if I hold a light throttle at 82mph 5th gear 3200rpm-3400rpm then a definate hesitation. I have had this from when I bought the car, Ian at RVT has tried Lamba,HT,Sparks, a 12k service and now in for 6k service to hopefully cure. If still a problem taking it to TrackVRoad to get a second opinion...

[Whitey]

TuscSam said:

I have a similar problem, if I hold a light throttle at 82mph 5th gear 3200rpm-3400rpm then a definate hesitation. I have had this from when I bought the car, Ian at RVT has tried Lamba,HT,Sparks, a 12k service and now in for 6k service to hopefully cure. If still a problem taking it to TrackVRoad to get a second opinion...

Sounds like worn throttle bodies.

[PetrolHeadPete]

So what's the issue with that Whitey, is it the air getting in around the spindles ? How worn is worn...mine seem pretty tight and butterflies sync nicely when pushing the throttle lever

[Whitey]

Pete I can't help on that sort of mechanical level, all I know is the throttle bodies wear and the spindles flex slightly throwing the throttle pots out which causes the slight uneven running.

I think early cars did not have bushes in the throttle bodies, but very late cars did.

A few places fit bushes to the throttle bodies to resolve this, otherwise it's a case of engine tuning to keep things running best as possible.

[TuscSam]

Thanks Whitey will ask Ian to Check if the Throttle Bodies have bushes, if not then ask to replace if possible. Thanks Again

[Night Rider]

Your problem might not just be the spindle bushes. I know my throttle bodies are sucking from 3-4 & 5 where they meet the head.

[stillgrinning]

Whitey said:

TuscSam said:

I have a similar problem, if I hold a light throttle at 82mph 5th gear 3200rpm-3400rpm then a definate hesitation. I have had this from when I bought the car, Ian at RVT has tried Lamba,HT,Sparks, a 12k service and now in for 6k service to hopefully cure. If still a problem taking it to TrackVRoad to get a second opinion...

Sounds like worn throttle bodies.

I have never heard my problem described so well ! I asked Power to check the throttle bodis the last time it had a service and they said they were all ok. It's due in for a service next month so I would like to point them in the right direction this time !

Ian

[tu51john]

HHC fixed it - no suprises there then. Not sure exactly what it was as Im no expert but it was the Throttle Bodies.

As much as I could understand they were loose??!!

Well thats the bit I understood anyway.

Car is now amazing.