Author Topic: Car misfire / cuts out at full throttle  (Read 3134 times)

MATT BLACK

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Car misfire / cuts out at full throttle
« on: 21:45, Sun 07 November 2010 »
OK - built the carb back up and refitted it and took it for a run.

In 1st, 2nd and 3rd gear the car pulls really strong but when changing to 4th and 5th on hard acceleration the car backfires / misfires / stalls for a split second and then comes back to life again - sometimes it will do it a few times so i back off. I've turned the boost down via the brass bleed valve and now its just nudging the first digit of the red section of the boost gauge  ( 13 psi ? ) and now it pulls OK all the way to top end.

Do you lads think this is the boost control valve on the intercooler hose cutting the power ( I've turned the little screw down on the inside all the way ) or could it possibly be something else ?

It was doing this before i jetted the carb - ive fitted new plugs, leads, dist cap, rotar arm etc.

Also if im running 15 psi on the standard T2 were about's on the boost gauge should the needle be touching ?


Any ideas ?

Ash-Lee

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Re: Car misfire / cuts out at full throttle
« Reply #1 on: 22:52, Sun 07 November 2010 »
Carb emptying or running lean?

Is the carb in standard form?

James5

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Re: Car misfire / cuts out at full throttle
« Reply #2 on: 23:07, Sun 07 November 2010 »
This does sound like the OE boost hoses overboost sensor cutting in, personally I would just take the wiires out of the sensor and tie them up out of the way.  Also have you got a wideband kit to see what the fueling is like yet??

MATT BLACK

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Re: Car misfire / cuts out at full throttle
« Reply #3 on: 08:31, Mon 08 November 2010 »
Quote from: "Ash-Lee"
Carb emptying or running lean?

Is the carb in standard form?


The carb is totally standard except for the 2nd stage jet which ive drilled out to 1.1mm. Ive also stripped the carb this weekend and rebuilt it with a new gasket / seal kit.

MATT BLACK

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Re: Car misfire / cuts out at full throttle
« Reply #4 on: 08:47, Mon 08 November 2010 »
Quote from: "James5"
This does sound like the OE boost hoses overboost sensor cutting in, personally I would just take the wiires out of the sensor and tie them up out of the way.  Also have you got a wideband kit to see what the fueling is like yet??



This is what i thought as the problem only occurs on full throttle when the brass bleed valve has been turned up ever so slightly. When i turn it back down to the setting its at now its fine, so im thinking the overboost valve is kicking in.

I will give it a whirl later on. I havent got a wideband kit yet sorry so im unsure of the afr. It does seem to be better though at full boost with the 2nd stage jet drilled to 1.1mm - on full throttle the boost kicks in a little more aggresive and the power delivery is smoother and constant - it just wants to go !!

The car is currently boosting to this level - im going to rig up a seperate, more accurate boost pressure gauge today to obtain a better reading.


James5

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Re: Car misfire / cuts out at full throttle
« Reply #5 on: 08:57, Mon 08 November 2010 »
Post your Result's Mat once you have had a play, also when installing a new boost gauge run the next one from the carb base i.e. "T " it into the AEI vacum line this will give you a more accurate reading to what your engine is getting as you loose about 4psi through the carb, but don't forget that you don't want to exceed 16psi on a T2 matey and that's carb top so that will be 12psi manifold :D

MATT BLACK

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Re: Car misfire / cuts out at full throttle
« Reply #6 on: 09:06, Mon 08 November 2010 »
Ok - thanks for your help

Just a quickie ...... with the 2nd boost gauge plumbed into the carb base and AEI unit will max boost for a standard T2 show on the gauge at 12psi or 16 psi ?

James5

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Re: Car misfire / cuts out at full throttle
« Reply #7 on: 09:48, Mon 08 November 2010 »
Quote from: "MATT BLACK"
Ok - thanks for your help

Just a quickie ...... with the 2nd boost gauge plumbed into the carb base and AEI unit will max boost for a standard T2 show on the gauge at 12psi or 16 psi ?


Plumbed in @ carb base you only want it to show 12psi max this will be your 16psi @ carb top

MATT BLACK

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Re: Car misfire / cuts out at full throttle
« Reply #8 on: 09:52, Mon 08 November 2010 »
Ok - thanks James

James5

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Re: Car misfire / cuts out at full throttle
« Reply #9 on: 10:11, Mon 08 November 2010 »
Quote from: "MATT BLACK"
Ok - thanks James


Your welcome, I still recomend you get a decent wideband kit just to make sure your fueling is ok for this boost level, also worth getting a decent intercooler aswell to assist with keeping charge temps down, if you want an OE replacement location intercooler I highly recomend the GTTuning double cap intercooler or otherwise known as the breadbin.

MATT BLACK

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Re: Car misfire / cuts out at full throttle
« Reply #10 on: 10:54, Mon 08 November 2010 »
I've fitted a pace intercooler which seems to be doing the trick.

Whats your recommendations on the air filter. It did have a green filter fitted but ive removed it as it was right next to the Turbo ( sucking in hot air ) and there didnt seem to be a decent cold air feed to supply it with o2. The previous owner had also removed the turbo / exhaust manifold heat shield so the green filter was about 10mm from the turbo.

Ive fitted a new heat shield from Renault ( yes they are still available - part no 6001009529 ) and ive refitted the standard air box with cold air feed - it seems a lot better.

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Re: Car misfire / cuts out at full throttle
« Reply #11 on: 11:38, Mon 08 November 2010 »
Quote from: "MATT BLACK"
I've fitted a pace intercooler which seems to be doing the trick.

Whats your recommendations on the air filter. It did have a green filter fitted but ive removed it as it was right next to the Turbo ( sucking in hot air ) and there didnt seem to be a decent cold air feed to supply it with o2. The previous owner had also removed the turbo / exhaust manifold heat shield so the green filter was about 10mm from the turbo.

Ive fitted a new heat shield from Renault ( yes they are still available - part no 6001009529 ) and ive refitted the standard air box with cold air feed - it seems a lot better.


Personally I would move the header tank to another location and make your own box and put in a nice big green air filter or K&N cone type.  
Something like this on my 5


Failing that and if you are still using OE position bits, OE air box with a K&N filter will be fine as the air is ram air effect in and the filter is protected from the heat of the turbo and engine bay by the metal box.  I would also not attach the rear heat shroud pipe to the OE box but screw it up so that flap does not open at all so just the cold air from the ram air feed will be going in

MATT BLACK

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Re: Car misfire / cuts out at full throttle
« Reply #12 on: 13:29, Mon 08 November 2010 »
That is a nice set up !!!


With regards to the OE air filter that is exactly what i have done. I've removed the second air inlet / outlet on the back of the filter housing and blocked the internal section of it off so its a direct cold ram air feed straight to the filter.

MATT BLACK

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Re: Car misfire / cuts out at full throttle
« Reply #13 on: 18:58, Mon 08 November 2010 »
Boost pressure sensor was the culprit. Just disconnected the wires and its fine now.

I've rigged a more accurate boost pressure gauge up to the carb base and AEI unit and mounted it on the O/S A pillar

The car seems to run really well at 16psi / 1.1 bar ( carb base ) but when you wind it down to your recommended 0.8 bar / 12 psi ( carb base ) it feels pretty much standard ?

What do you think ?

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Re: Car misfire / cuts out at full throttle
« Reply #14 on: 09:36, Tue 09 November 2010 »
Quote from: "MATT BLACK"
Boost pressure sensor was the culprit. Just disconnected the wires and its fine now.

I've rigged a more accurate boost pressure gauge up to the carb base and AEI unit and mounted it on the O/S A pillar

The car seems to run really well at 16psi / 1.1 bar ( carb base ) but when you wind it down to your recommended 0.8 bar / 12 psi ( carb base ) it feels pretty much standard ?

What do you think ?


LOL that's becuase you have used it at 16psi manifold which will feel alot more lively if you want to run the t2 @ 16psi manifold you need to make sure you have the fueling for it and decent charge temps as the little T2 compressor will only be throwing hot air through the system.

I think standard boost is 10psi carb top so that will be about 6psi carb base (been so long since I have seen or been in a car with standard boost :lol: )