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Jerky Spooling


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#1 Dont_tell_him_pike

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Posted 24 June 2011 - 01:10 PM

When accelerating uphill, the car jerks quite unpleasantly, in a manner similar to fuel cut though less violent. Once it passes about 3500rpm (or reaches full boost?) it accelerates smoothly.

I wondered if it was a spark plug issue as they've been in need of replacing for a while, but a new set hasn't helped.

Yesterday I tried unhooking the turbo actuator, effectively running the car as an N/A, this made the jerkiness go away, so it would seem to be a boost issue. Adjusting the boost level doesn't help matters, as it only seems to happen while the turbo is spooling.

Can anyone suggest any possible/likely causes?

Thanks!
Confucius say, "He who uses a duck umberella as a bonnet prop shall, in time, inevitably feel the wrath of his bonnet"

The Red Sera 1.5 turbo
The Blue Sera 1.5 turbo - RIP

#2 Graham

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    Sydney, Australia. Sera now with turbo :)

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Posted 25 June 2011 - 02:16 AM

It sounds a bit like an occasional mis/no-fire on one or more cylinders.

Just as a theory or 2:
Breakdown in in the ignition leads ?
Ignition coil needs replacing ??
Don't know why either would go away after 3500rpm though.

Cheers, G.

#3 Mork

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Posted 25 June 2011 - 04:34 PM

Perhaps a blockage in the air intake? Although doubtful, but other than fuel, air and ignition, what else is there? What about the dizzy and rotor arm? Have you checked cylinder compression? What's the condition of the actuator? Do you still have the boost solenoid attached? Sticking throttle? Just a few ideas to explore if you haven't already.

#4 Dont_tell_him_pike

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Posted 27 June 2011 - 12:06 AM

New plugs and leads, dizzy is a possibility. Actuator still feels right. Thing is, not sure if these things would still affect it with the wastegate open. i got thinking i've not changed the fuel filter since getting the car, so it's at least 18 months old, maybe a lot older, so gonna try a new one, see if that sorts it. if it doesn't than it'll still be a good thing to have done, like the plugs. next (if there is a next...) I'll try removing the dump valve, see if it's that...
Confucius say, "He who uses a duck umberella as a bonnet prop shall, in time, inevitably feel the wrath of his bonnet"

The Red Sera 1.5 turbo
The Blue Sera 1.5 turbo - RIP

#5 Dont_tell_him_pike

Dont_tell_him_pike

    loves his duck brolly...

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Posted 30 June 2011 - 07:58 PM

Turned out to be stupidly simple - a hole in the hose for the map sensor. It was right at the top, so all I had to do was snip a bit off. This was after spending 150 odd on new parts. Still, at least the car won't need a service for a while!
Confucius say, "He who uses a duck umberella as a bonnet prop shall, in time, inevitably feel the wrath of his bonnet"

The Red Sera 1.5 turbo
The Blue Sera 1.5 turbo - RIP

#6 Mork

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Posted 30 June 2011 - 09:13 PM

It's always the simple things! I lost power last week after boost, thought the worst cos it wouldn't boost. Found the boost pipe had popped of the boost sensor. Fitted a new, tighter fitting silicon hose, job's a good un.




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