P38A Judder

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Dopey

Well-Known Member
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6,201
Location
Heathrow
I am thinking this is the fuel pump injector pump, from cold, as I drive along, its fueling and then not fueling, so it accelerates and then doesn't for a second, so its kink of juddering along, and not a lot of power at all for the first few meters, changed the sealed a few years back (all but the bottom one) and its not leaking or smelling, I have another issue with the power steering now as well, but thats another post!! just need some thoughts about what it could most likely be so I can have a look at it again
 
I think we're all waiting to see what Wammers says!

Have you checked for air in the clear pipe from the fuel filter? Maybe the lift-pump has died?

Might be worth diagnostics too. Was wondering if #4 injector could be playing up.
 
#4 is new, and works fine, the pipe is almost new as well, I changed it, but was told it didn't matter if there was air in it anyway, even when it did have air in it, it was working fine, you mean the lift pump in the tank? changed that as well
 
No air in my fuel pipe. Yes, I was thinking of the lift pump. Easy to check using Wammer's How To. New parts can fail. Yours is younger than mine IIRC.

Beyond my ken then. I'd be thinking maybe MAF with loss of power but I'm just having a wild stab in the dark. Have you got a Nanocom?
 
No air in my fuel pipe. Yes, I was thinking of the lift pump. Easy to check using Wammer's How To. New parts can fail. Yours is younger than mine IIRC.

Beyond my ken then. I'd be thinking maybe MAF with loss of power but I'm just having a wild stab in the dark. Have you got a Nanocom?

Nothing to do with MAF i can assure you of that. His car doesn't have one and it wouldn't be that if it had. If the lift pump is sound and working diag may throw something up, my crystal ball is away for cleaning.
 
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Well I have been round and we have plugged in the rovacom lite and read the faults and it came up with one
boost pressure invalid value,(rpm=32,injector flow+39),too high, too low, invalid value, major fault, fault logged,current, intermittent, occurances =15
I haven`t a clue what that means, but when cold you go to pull away no power, you can bury the throttle and hardly get any response then after a few seconds it will take of as normal
I have some other screen printouts for info if any one can shed some light.
 
Well I have been round and we have plugged in the rovacom lite and read the faults and it came up with one
boost pressure invalid value,(rpm=32,injector flow+39),too high, too low, invalid value, major fault, fault logged,current, intermittent, occurances =15
I haven`t a clue what that means, but when cold you go to pull away no power, you can bury the throttle and hardly get any response then after a few seconds it will take of as normal
I have some other screen printouts for info if any one can shed some light.

Would hazard a guess that the mid section of the pump is in the wrong place.
 
Would there be anything else on diag that will tell us more or a what should we check.
Maybe compared fuel quantities. If the mid section is in the wrong place it will be getting to little or to much start fuel and idle fuel the ECU will be adjusting the fuel quantity to suit the preset idle speed. So there should be a difference in the actual and compared quantities. Sounds like the ECU is having problems figuring out how much fuel is needed when throttle is moved above idle control position (idle switch closed) and into throttle request mode. So he is getting an hesitation. Have a look what the idle setting is should be rock steady 750 RPM with a setting of 128 on pump settings. If it's lower than 128 at 750 RPM mid section is in wrong place giving to much fuel. If it's higher than 128 mid section is in wrong place giving to little fuel.
 
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Brian, you can record a trace with the Nanocom in each of the fuel menus. Get it nice and warm and then just record a trace at idle for a few minutes. If you do that I'll compare it with mine.
 
The rovacom lite runs with a laptop I saved screen shots to excel worksheet, hopefully it can be read.
 

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  • edc..pdf
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I think the current fuel quantity is a little low on page 1. So that could be the FIP or lift pump acting up?
Setpoint not far out compared to mine.
Injector degrees seems to be within 0.5 so presumably OK.
Timing modulation a little high but not worryingly high.
Atmospheric pressure 100 looks like a default? Or is it the year? mine varies a bit over a long recording but is never exactly 100. Probably not worth worrying about.
Throttle pot looks OK.
Wish my battery looked like that.

Over to the gurus!
 
Can anyone shed some light on this for me please? so I can fix this, thanks to everyone's help so far
 
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