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Discussion Starter · #1 ·
Hi all, I’m new to this forum but have found the information on here invaluable!
Managed to change my own gearbox and rear diff oil because of this page!

Introduction aside, only recently my fiat 124 spider lusso plus (I live in the UK) has been playing up when I put my foot down and reach boost!
From 3k revs the whole car will judder and jerk as it goes up the rev range, I’m pretty sure I don’t have an issue with the boost it’s self as it will happily climb to redline but it is jerky.
My suspect it either the diverter solenoid or the wastegate.

I was wondering if anyone had experienced anything similar and what the actual problem was.

My car is serviced all by me so I know what’s been done and all that malarkey and change the oil every 3k (own peace of mind and a touch of OCD) so have ruled out usually suspects if anything!

Thankyou in advance
Jacque
 

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Welcome to the forum. The first thing I'd do is check for boost leaks. There is a good thread on this forum on how to do that. If it were misfires the car would throw a code so I don't think that's the issue. You might have a leaky diverter valve. The fix is replacing that with a GFB DV+ diverter valve. It's easy and cheap to do. You don't by chance have a throttle booster installed do you? If so, disconnect it and see if that cures the problem.
 

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My brain initially went to boost issue or electronic throttle controller as well. If there is no pedal booster, throttle controller may still be worth looking at.
 

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Discussion Starter · #5 ·
Welcome to the forum. The first thing I'd do is check for boost leaks. There is a good thread on this forum on how to do that. If it were misfires the car would throw a code so I don't think that's the issue. You might have a leaky diverter valve. The fix is replacing that with a GFB DV+ diverter valve. It's easy and cheap to do. You don't by chance have a throttle booster installed do you? If so, disconnect it and see if that cures the problem.
Noo the cars completely standard apart from a back box delete I did 2 years ago
 

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Discussion Starter · #6 ·
My brain initially went to boost issue or electronic throttle controller as well. If there is no pedal booster, throttle controller may still be worth looking at.
I’m not too sure where abouts the throttle controller would be? It’s had to explain haha, it’s like the boost can’t get through
 

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If you don't know then you don't have one. It's an aftermarket part you would have added. Try the boost leak testing first and see what that tells you.
Maybe he is a good candidate for the part I suggested. What do you think?
 

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Discussion Starter · #9 ·
If you don't know then you don't have one. It's an aftermarket part you would have added. Try the boost leak testing first and see what that tells you.
I will order a boost tester, but out of curiosity, what does the dv+ thing replace or is it just an add on part?
 

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I will order a boost tester, but out of curiosity, what does the dv+ thing replace or is it just an add on part?
It is a add-on part for the diverter valve
 

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Discussion Starter · #12 ·
The GFB DV+ is not an add-on but replacement of the critical components. It is virtually standard practice amongst owners of this car. The OEM unit is low quality and problematic....... the issues you describe are similar to the problems I experienced until I fitted the GFB DV+. Do it anyway !!!!
Ohh this fills me with a bit of Hope then! 🤣 thankyou! Ill get it ordered does anyone have a link so that I order the correct one?
thanks in advance
 

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I've been playing around with boost leaks tonight. I was originally getting air escaping at 19psi from the ic outlet connector. This did not seems to affect driving and there was nothing like you describe. Acceleration fine and boost holding at 23psi plus. I think you'd need to see a serious leak to get what you are seeing.

After fiddling with the flange bolts and using a fabricated clamp on the long side of the flange, I now dont hear leaks until 22psi and I can get 23.5 with my tyre pump.

My guess for you may be the wastegate solenoid (3 way), wastegate itself or some pretty bad misfiring.

If boost pressure vs demanded is hugely different then there is usually a code thrown?

Can you get an obd plugged in and monitor some stuff?

Where in UK are you @Jtk1236 ?

Chainring is obviously more knowledgable than me so listen to him first! but just my 2 cents :)
 
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You can also consider this part that is a direct replacement of the part.
 
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I'd really get a reader plugged in and monitor boost, fuel trims and some other stuff on wot before throwing money at parts !
 

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I'd really get a reader plugged in and monitor boost, fuel trims and some other stuff on wot before throwing money at parts !
Also a very true statement, will consider that first. you don't want to play with a possible warranty issue before doing changes. If it is stock you should probably test it out first and then consider other parts. Make sure everything works in stock first.
 
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Discussion Starter · #18 ·
I've been playing around with boost leaks tonight. I was originally getting air escaping at 19psi from the ic outlet connector. This did not seems to affect driving and there was nothing like you describe. Acceleration fine and boost holding at 23psi plus. I think you'd need to see a serious leak to get what you are seeing.

After fiddling with the flange bolts and using a fabricated clamp on the long side of the flange, I now dont hear leaks until 22psi and I can get 23.5 with my tyre pump.

My guess for you may be the wastegate solenoid (3 way), wastegate itself or some pretty bad misfiring.

If boost pressure vs demanded is hugely different then there is usually a code thrown?

Can you get an obd plugged in and monitor some stuff?

Where in UK are you @Jtk1236 ?

Chainring is obviously more knowledgable than me so listen to him first! but just my 2 cents :)
No codes been thrown up, and it doesn’t feel down on boost just that it doesn’t apply it smoothly, definitely feels like somethings flapping away.

im from Warrington in Cheshire by the way 😁
 

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Ah OK. I am up in Cumbria. Was gonna offer to have a look and bring down my ECUscan to log some runs. But obvs a bit tricky with the current distancing stuff!

I wonder if it is either diverter valve or possibly wastegate.
 
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Discussion Starter · #20 ·
Ah OK. I am up in Cumbria. Was gonna offer to have a look and bring down my ECUscan to log some runs. But obvs a bit tricky with the current distancing stuff!

I wonder if it is either diverter valve or possibly wastegate.
I thought waste gate too, but I just can’t see that being it, I use my spider everyday and since this hot weather that’s when it’s been playing up!
I’ll get the new diverter valve anyway because it’s been on my list for awhile
 
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