LCR High / Lumpy Idle, Persistant 17705 Fault Code

[Gaz20VT]

My 2003 LCR is showing a persistent 17705 fault code, the "pressure drop between turbo and throttle" error. This does not clear, even when clearing the codes with the engine running.


As the car warms up, the idle becomes lumpy, then starts to increase, up to 1250-1300RPM. Clearing the codes with the engine running causes the idle to temporarily drop, then increase again.

I have copied the screenshots below from VCDS Lite, showing the main measuring blocks. The car had been running for approx. 10 minutes before these were taken:-

Readiness Status:-

Blocks 001, 002, 003

Blocks 004, 005, 006

Blocks 010, 011, 014

The right-hand item in Block 014 changes from Enabled to Disabled intermittently.

The car is a completely standard 210 AMK LCR apart from some silicone breather hoses between block/cam cover and pancake valve, and a Forge TIP.

The breather pipework under the manifold is present, the suction jet pump and the one-way breather valve are virtually new. Recirculation valve is a few months old, and an OEM 710P from Listers SEAT.

I've made the following checks so far:-
- Checked vacuum/pressure hoses for signs of damage - nothing obvious.
- Checked hose clips for tightness - all OK.
- Removed DV and blocked inlet/outlet hoses - no change.
- Disconnected vacuum hose from recirculation valve - no change.
- Disconnected the servo hose from the left hand end of the manifold - no change.
- Disconnected the vacuum hose from the top of the throttle body - no change.
- Tried second used MAP sensor (existing one had been damaged by what looks like a botched removal attempt) - no change.

I'm running out of ideas now, does anyone see anything obvious from the above? Would a smoke test help?

Ideas welcomed!

 

[Andrewwright]

My 2003 LCR is showing a persistent 17705 fault code, the "pressure drop between turbo and throttle" error. This does not clear, even when clearing the codes with the engine running.
View attachment 6420

As the car warms up, the idle becomes lumpy, then starts to increase, up to 1250-1300RPM. Clearing the codes with the engine running causes the idle to temporarily drop, then increase again.

I have copied the screenshots below from VCDS Lite, showing the main measuring blocks. The car had been running for approx. 10 minutes before these were taken:-

Readiness Status:-
View attachment 6416
Blocks 001, 002, 003
View attachment 6417
Blocks 004, 005, 006
View attachment 6418
Blocks 010, 011, 014
View attachment 6419
The right-hand item in Block 014 changes from Enabled to Disabled intermittently.

The car is a completely standard 210 AMK LCR apart from some silicone breather hoses between block/cam cover and pancake valve.

The breather pipework under the manifold is present, the suction jet pump and the one-way breather valve are virtually new. Recirculation valve is a few months old, and an OEM 710P from Listers SEAT.

I've made the following checks so far:-
- Checked vacuum/pressure hoses for signs of damage - nothing obvious.
- Checked hose clips for tightness - all OK.
- Removed DV and blocked inlet/outlet hoses - no change.
- Disconnected vacuum hose from recirculation valve - no change.
- Disconnected the servo hose from the left hand end of the manifold - no change.
- Disconnected the vacuum hose from the top of the throttle body - no change.
- Tried second used MAP sensor (existing one had been damaged by what looks like a botched removal attempt) - no change.

I'm running out of ideas now, does anyone see anything obvious from the above? Would a smoke test help?

Ideas welcomed!

Smoke test is the way forward. Save you time and headache.

Sent from my Nexus 6 using Tapatalk

 

[Gaz20VT]

Anyone recommended near Basildon for a smoke test? Is DIY possible?

 

[Connorg115]

Hi i used a empty paint can and put a plumbers smoke bomb in and blew into the intake (one pipe onto an inlet the other i blew in through)



Put a rubber glove over the intake pipe

I used the inlet on the throttle body (circled) to blow into

 

[Gaz20VT]

Thanks for the suggestions so far, guys. Smoke test done, thanks to the DIY smoke tester (a Bisto jar and two tyre valves - will make improvements to it when I have time). Found one split hose below the manifold. Temporarily taped that up with self-amalgamating tape.


Put the manifold back on, cleared the codes and started the car, hoping I'd fixed it. Nope, still lumpy at warm idle and showing the 17705 error. The only component I hadn't ever inspected was the turbo outlet hose. Blocked one end with a round plastic shipping cap, and pressurised the other end with a shipping cap with another tyre valve in it, for a soapy-water bubble check.

Difficult to get a picture whilst holding it down, but this seems to be leaking too! Will replace this one, and see what happens.

With the suction jet pump and PCV system in place (which I don't want to remove) is it possible to boost leak check by pressurising the inlet, or will there always be a leak to the sump or back into the TIP? I guess there will always be one cylinder with its inlet valves open, too.

 

[Gaz20VT]

So, have tested further using the DIY smoke tester, boost leak testing, and some other methods to try to find out what's causing the issue.

The smoke test didn't show anything leaking externally, neither does pressurising the inlet tract with the TIP blocked off. That only showed that the oil filler cap is the first part to leak, followed by the half-moon blanking plug in the inlet cam side of the head.

The one way valves in the servo and charcoal canister lines seem to work properly.

One thing noticed during the testing, the N249 is applying vacuum to the DV with the engine idling - is that normal or do I have an N249 fault?

 

[Gaz20VT]

So, just to update this a bit, just for thread completeness.

Got fed up with trying to smoke test or find the leak on the car as nothing was showing up, so I took the manifold off again and screwed it to a piece of wood, with a rubber sheet for a gasket. Blocked off the various spigots with caps and pipes, and put the injectors back in to seal the holes, with the intention of finding leaks using soapy water and compressed air.



Putting pressure in through the throttle body spigot showed a big leak through the plastic PCV (genuine, only 3 months old), but also through the Inlet Air Temperature sensor O-ring.


A spare O-ring has fixed that leak, and a set of Forge hoses has replaced the split one I previously taped up. The manifold now holds 10PSI comfortably before one of a number of my plastic caps disappears across the garage and makes me jump!



Will replace the PCV with a metal one, and fit it all back to the car this weekend to see if that sorts it!

 

[mty12345]

Very useful info mate.... I'll be fitting a new o-ring to my IAT sensor at the weekend just to be sure after reading this,lol

 

[Gaz20VT]

Despite the replacement O-ring, it seems to be leaking through the body of the sensor as well, so I'll be fitting a new sensor. Billet PCV arrived today and has successfully plugged the breather leak. Next step, back onto the car.

 

[Gaz20VT]

Right, part is back on the car aaaaaand........

No different. Still getting an error code immediately on startup which clears then immediately re-appears. When the fault is cleared, the idle changes - the revs increase and then drop down again, after which the fault code is back.

I have cleaned the throttle body but not performed an alignment - is this likely to be the bit I'm missing?

 

[mty12345]

When the fault is cleared, the idle changes - the revs increase and then drop down again, after which the fault code is back.

Clearing the codes deletes the current fuel trims, it takes a few cycles for it to re-adjust, hence the idle change.

I have cleaned the throttle body but not performed an alignment - is this likely to be the bit I'm missing?

Quite possibly, i would definitely do it before chasing any other causes.

 

[Gaz20VT]

Clearing the codes deletes the current fuel trims, it takes a few cycles for it to re-adjust, hence the idle change.



Quite possibly, i would definitely do it before chasing any other causes.

Fair enough, it makes sense. I'm happy there are no leaks and the N75, N249 and other usual bits are working properly.
Anyone close to Basildon with a licensed VCDS?

 

[Gaz20VT]

Progress, I think. Realigned TB, the value in the left hand duty cycle changed from 14.something to the 10.8% shown. Forgot to take a screenshot before the align was started.



After a thorough road test (for that read John Cleese-style flogging) I now have a N249 Mechanical Malfunction code - 17608. I could hear the turbo going into compressor surge on lift-off, whereas it wasn't doing that before.
I have a spare N249 so I'll fit that and try again.
Cars, eh? Who'd have 'em?

 

[Gaz20VT]

Final update, car now fixed. lift-off surge was because I'd nipped the vacuum line from the manifold to the N249 when refitting the EGT sensor box under the manifold........
Now running better than ever!

 

[mty12345]

Final update, car now fixed. lift-off surge was because I'd nipped the vacuum line from the manifold to the N249 when refitting the EGT sensor box under the manifold........
Now running better than ever!

Glad to hear that it's all sorted buddy!