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TDCI surging under full throttle - sticky vanes? [with logs]

6K views 13 replies 6 participants last post by  grandaddy_low 
#1 ·
Hi,

Mondeo Mk4 and Galaxy Mk3. Same engine in both, both surge on full throttle. Feels like the turbo dumps the boost then recovers but then keeps doing that. Never does it cold, only when the engine is hot. The hotter the engine is, the worse it is.

- MAF cleaned. No difference

- Vacuum supply pressure checked.

- Boost control solenoid replaced as it was a bit leaky. Didn't make any difference.

Attached are some logs:

- cold pull - works fine

- warm pull - you can see the vane position voltage spike, then the MAF and MAP react afterwards.

- cruise - 70 on the motorway. No noticeable surging.

I'm thinking clogged vanes, but they are a pain to get to, so before I get into that, is there anything else I should be looking at first?

Thanks GDL.
 

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#11 ·
I'd be looking at the pressure converters. There are two. One controls the EGR I think and the other the variable vanes. When the pressure converter than controls the turbo starts to fail you get this surging, sometimes at constant throttle sometimes under strong acceleration.

Often before the converter fails it starts making a "mooing" sound when you shut the engine off.
 
#12 ·
I'd be looking at the pressure converters. There are two. One controls the EGR I think and the other the variable vanes. When the pressure converter than controls the turbo starts to fail you get this surging, sometimes at constant throttle sometimes under strong acceleration.

Often before the converter fails it starts making a "mooing" sound when you shut the engine off.
Hi can you expand on this?

Mine is making that noise, and is also surging under heavy acceleration.

Where are these located, and how do you check them. Do you know the part numbers etc?
 
#13 ·
I'd be looking at the pressure converters. There are two. One controls the EGR I think and the other the variable vanes. When the pressure converter than controls the turbo starts to fail you get this surging, sometimes at constant throttle sometimes under strong acceleration.

Often before the converter fails it starts making a "mooing" sound when you shut the engine off.
This is the turbo boost control solenoid. I think the OP said he replaced it already.

My initial feeling is this is a fuel pressure issue.
 
#14 ·
I did have a fuel pump go bad on it. I replaced it (with a used one). I'm sure I've checked fuel pressure and found it to be OK, but I'll do it again when we're allowed out again.

The EGR and boost control solenoids have been replaced. That said, one of the new ones was completely broken when it arrived. I'll re-check them too and post back.
 
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