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Discussion Starter #1
Morning all,

I took the GTA for a dyno on saturday and since then its started juddering/stutterting violently at high RPM and flashing the MCSF light briefly. but its doing it at various RPM, did it a 5k last night, so its not the limiter, but it doesnt do it out of gear.

I checked for fault codes and there were none, not even historic ones.

Any ideas why this would be happening?

Link to the dyno run and the spit of flame which makes me think they didnt hit the limiter, instead the engine did this juddering instead?

https://www.flickr.com/photos/[email protected]/sets/72157645785147725/

PS. I'm posting a lot recently and really appreciate the responses/advice, and I try to help out where I can :)

Sam
 

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Didn't you fit CF2s recently? And no map?

I personally would put it down to that it's running very very lean, mine ran very lean when I went with CF2s with no map. Get the map sorted ASAP as you could be gradually nuking the engine.

Give Gus a call, he'll sort it out for you. You can even send your ECU to him :)

I really wouldn't be driving around if I was you, or if you need to, drive it like a granny till it's mapped :)

Hope that helps :)
 

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Discussion Starter #3
Didn't you fit CF2s recently? And no map?

I personally would put it down to that it's running very very lean, mine ran very lean when I went with CF2s with no map. Get the map sorted ASAP as you could be gradually nuking the engine.

Give Gus a call, he'll sort it out for you. You can even send your ECU to him :)

I really wouldn't be driving around if I was you, or if you need to, drive it like a granny till it's mapped :)

Hope that helps :)
This makes sense, but it didnt cross my mind as it didnt occur before?

But if I can send him my ECU I'll get it done this week, was under the impression he needed the vehicle?

Thanks BB
 

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This makes sense, but it didnt cross my mind as it didnt occur before?

But if I can send him my ECU I'll get it done this week, was under the impression he needed the vehicle?

Thanks BB
Maybe doing the dyno run set off some sort of alarm but not sure tbh.

He can do it without the car, which was handy for me as his at the other end of the country from me :)
 

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Discussion Starter #5
Maybe doing the dyno run set off some sort of alarm but not sure tbh.

He can do it without the car, which was handy for me as his at the other end of the country from me :)
Hmm maybe, as long as its fixable nothing to worry about then.

Thanks matey
 

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Link to the dyno run and the spit of flame which makes me think they didnt hit the limiter, instead the engine did this juddering instead?

https://www.flickr.com/photos/[email protected]/sets/72157645785147725/
That was a big bang, any ideas where in the rev range that happened? Lot of fuel in the exhaust for that to happen, so it can't be consistently lean. Did they not do the rolling road run with an AFR gauge in the exhaust? That would indicate rich/lean.
 

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Discussion Starter #7
That was a big bang, any ideas where in the rev range that happened? Lot of fuel in the exhaust for that to happen, so it can't be consistently rich. Did they not do the rolling road run with an AFR gauge in the exhaust? That would indicate rich/lean.
Yes it was ha, although I'm not finding it quite as amusing now...

No they didnt use a probe, but it was done through a friend so they slipped me in between other customers. But the first run went fine :confused:

Im in the middle of trying to organise a remap through Gus and getting him to check it over too. Damn work hours are making it difficult though...
 
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That is a hell of a bang!

The fella working on the car next door neat had kittens.

That isn't right!
 

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Yes it was ha, although I'm not finding it quite as amusing now...

No they didnt use a probe, but it was done through a friend so they slipped me in between other customers. But the first run went fine :confused:

Im in the middle of trying to organise a remap through Gus and getting him to check it over too. Damn work hours are making it difficult though...
Sorry I should have said "consistenly lean" in my first post rather than "consistently rich".

If your stuttering/juddering has come only since the rolling road run then there is a possibility something physically may have gone wrong and caused that bang and the issues you've been having since. I would pull the plugs again and see if you can see any telltale signs of misfiring on a specific cylinder, or do a compression test if you have the equiptment.
 

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Morning all,

I took the GTA for a dyno on saturday and since then its started juddering/stutterting violently at high RPM and flashing the MCSF light briefly. but its doing it at various RPM, did it a 5k last night, so its not the limiter, but it doesnt do it out of gear.

I checked for fault codes and there were none, not even historic ones.

Any ideas why this would be happening?

Link to the dyno run and the spit of flame which makes me think they didnt hit the limiter, instead the engine did this juddering instead?

https://www.flickr.com/photos/[email protected]/sets/72157645785147725/

PS. I'm posting a lot recently and really appreciate the responses/advice, and I try to help out where I can :)

Sam
Based on what you're saying, I'm wondering if the cam timing has jumped? It would explain the flames out the exhaust and may not register as a fault code.

Sam, I've got GTA cam locks too if you want it checking. :thumbs:
 

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What Chris said. Check the timing then if all OK do a compression test. Doesn't take too long - only a couple of hours or so to do both.

I have not seen a GTA spit flames before!
 

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Discussion Starter #15

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Discussion Starter #16
Not exactly what I wanted to hear...

Strange how its done it on a rolling road with not much resistance, compared to 20 mins earlier on road...

Chris: Im using an OBD bluetooth thing of ebay, worked well recognising the coil pack issues and misfires last week. And may take you up on the locks offer mate.

Ok so how do I go about checking the timing? Timing light? And yes I've got a dial gauge comp tester.
 

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Strip the engine down to expose the cam shafts, remove the spark plugs, turn the engine to tdc on no 1 using a dti then fit the cam locks. If they don't fit, then the cam timing is out :(

Ill pm you my mob num.
 

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Discussion Starter #19
Ok so say the timing is out...god I hope not...

What's the next step? please don't tell me I have to take the engine out and pretty much do a cam-belt change?

Sam
 

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You can reset the timing with the engine in the car easy enough once its stripped for checking. I'd put a new belt & tensioner on it at the minimum at this point - and maybe the rest (idlers/waterpump) if they haven't been done recently.
 
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