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Low Throttle Stutter 

 

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 Post subject: Low Throttle Stutter
Posted: Fri Jul 30, 2010 7:04 am 
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Hey everyone,

I have always had, and now exacerbated by the blower, a low throttle percentage stutter. It used to be 100 times worse when the car was cold, seemed to go away when it all got hot. Now it seems to be there all the time, hot or cold.

By that, I mean when the car is moving off idle with the throttle barely cracked open it gets a miss. I've got the wide band O2 meter in the car now, and I can see it is severely underfueling at the same time.

As soon as it gets a bit more throttle its is back to normal and runs beautifully.


I have been told that it could be the TPS needing adjustment, and this seems to make sense to me. Does anyone else have any suggestions for what it could be?

How do I test the TPS too? From memory it is 0.2v at close and 5v at WOT, is that correct?

I also remember that back in the days when it was auto you would re calibrate the TPS by holding it in neutral at closed throttle for one minute then turn engine off and WOT for one minute in drive. Is there an equivalent for manuals? I'm running a proper manual ECU these days.


Cheers,
Nic

 

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 8:37 am 
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Yeah, i'd look at the spark plug leads. It's common that if you just touch the throttle and it misses, it's usually the leads. Test the resistance. It should be about 7,000 ohms per foot.

 

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 9:00 am 
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From memory, the TPS voltage is 0.7v closed and 4.5v at WOT

 

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 10:52 am 
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lee - the leads are brand new, as is the coil pack and plugs. Still an easy thing to test.


Kwik, thanks man.

 

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 12:35 pm 
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Hey Nicco,

Can you describe in detail how you recalibrate the TPS. My car has been doing the same but ive just turned up the idle to try correct it. Im sort of used to it now :?

Cheers.

 

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 12:50 pm 
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On the 2 cars I've had this happen in it has been the head gasket. Is yours still on the original? Noticed any other signs of a head gasket. Usually water in the bowel spark plug gets wet misses then when the water gets pumped out it sparks normal.

Hopefully its not

 

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 2:22 pm 
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93EB, i'll see what happens when I get home and have a play. If it seems to help I'll let you know.

Finnigan, I believe it's the original head gasket after 205000km ( :shock: ), so a good chance it could be going any time soon. I've owned the car since 120000km.

Having said that, its been doing this for literally years, the plugs weren't at all rusty when i removed them, it does have a slow coolant leak, but I have also found a crack in the radiator side tank.

Also, i would have thought if it is only a very slow weep, the water would be evaporated out of the cylinder very quickly after startup; ie: it would take a hell of a coolant leak to get the water to effect the spark.

 

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 4:18 pm 
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Yeah good point. One of mine had a pin hole leak in the actual spark plug thread and was running down the plug. The likelyhood of yours doing that is not likely. But worth a mention.

Also headers or manifold loose bolts? Can also contribute to these symptoms.

 

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XR low springs - Boge Turbo Shocks - Front DBA slotted Rotors - BA ESS shifter - Shift Kit

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 Post subject: Re: Low Throttle Stutter
Posted: Fri Jul 30, 2010 10:37 pm 
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nicco wrote:
Hey everyone,

I have always had, and now exacerbated by the blower, a low throttle percentage stutter. It used to be 100 times worse when the car was cold, seemed to go away when it all got hot. Now it seems to be there all the time, hot or cold.

By that, I mean when the car is moving off idle with the throttle barely cracked open it gets a miss. I've got the wide band O2 meter in the car now, and I can see it is severely underfueling at the same time.

As soon as it gets a bit more throttle its is back to normal and runs beautifully.


I have been told that it could be the TPS needing adjustment, and this seems to make sense to me. Does anyone else have any suggestions for what it could be?

How do I test the TPS too? From memory it is 0.2v at close and 5v at WOT, is that correct?

I also remember that back in the days when it was auto you would re calibrate the TPS by holding it in neutral at closed throttle for one minute then turn engine off and WOT for one minute in drive. Is there an equivalent for manuals? I'm running a proper manual ECU these days.


Cheers,
Nic

my brothers car use to stutter on take off or anytime he'd try and acclerate,turned out his lash adjuster for the cam chain was lose and it ended up letting go skiped a tooth and shatter the rockers down one side of the head

 

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 Post subject: Re: Low Throttle Stutter
Posted: Sat Jul 31, 2010 12:53 am 
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I had this exact problem, it would always stutter at the same point around the corner when I leave my house. I changed the oil and changed the fuel filter and air filter. bang easy, no stutter
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 Post subject: Re: Low Throttle Stutter
Posted: Sat Jul 31, 2010 6:33 am 
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I really appreciate all the suggestions guys.

I'm going to try and sift through the symptoms and get a reasonable diagnosis here.

Uniacid - Mine used to only do it when cold, the problem seems more pronounced though atm. Hence the concern. The fuel filter is only a few months old.

Mitch - Maybe, but i would have thought that would present more as a rattle though if the chain was that loose. Also, a loose chain wouldnt cause it to stop injecting fuel.

Rob - As with the above, the oil and air filter wouldn't cause it to stop injecting fuel. Fuel filter maybe, but this filter is newish and the problem preceeds the changeout.



To be honest, I'm still thinking the TPS might be out.



I'm just looking forward to getting home on Wednesday so I can have a play with it! :lol:


Thanks guys,
Nic

 

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 Post subject: Re: Low Throttle Stutter
Posted: Sat Jul 31, 2010 9:31 am 
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Maybe drop into see tickford_6, he may be able to diagnose the issue in no time flat

 

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