Intake air leak

[LB123]

After 300 miles warning light free I'm back with the usual faults. Plastic part of vacuum servo hose on 1.4 16v BBZ had split producing 17961,17912, 18265 and 01314. Replaced the hose early august and fault free.

Returning from Gym last night stopped at tesco for spuds and on restart it was hunting and trying to stall. Moved off very juddery and cut out, EPC and engine lights on yellow. Wouldn't bump start with the momentum of the car. Stopped. Switched off and on. Restarted but hunting 700-1100rpm. Switched off. Waited a couple of minutes while I thought of what to do. Tried a start. All fine. EPC went off. Done 20 miles since with car working normal.

Scan

Address 01: Engine        Labels: 036-906-034-APE.lbl
   Part No: 036 906 034 DF
   Component:  MARELLI 4MV        5020  
   Coding: 00031
   Shop #: WSC 13765  
   VCID: 59B2F764C320348C03-4B36
   TMBND46Y744131231     SKZ7Z0D2523094

2 Faults Found:
17961 - Barometric / Manifold Pressure Signals
            P1553 - 35-10 - Implausible Correlation - Intermittent
17912 - Intake Air System
            P1504 - 35-10 - Leak Detected - Intermittent
Readiness: 0000 0001

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: 6R0-907-37x-ASR80.clb
   Part No SW: 6Q0 907 379 AB    HW: 6Q0 907 379 S
   Component: MABS 8.0 front  H03 0001  
   Revision: 00000000    Serial number: 00000000000000
   Coding: 0000005
   Shop #: WSC 00000 000 00000
   VCID: 7DFA83F427C828AC4F-5140

2 Faults Found:
18265 - Load Signal
            P1857 - 000 - Error Message from ECU - Intermittent
             Freeze Frame:
                    Fault Status: 00100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 41
                    Mileage: 117247 km
                    Time Indication: 0

01314 - Engine Control Module
            013 - Check DTC Memory - Intermittent
             Freeze Frame:
                    Fault Status: 00101101
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 41
                    Mileage: 117247 km
                    Time Indication: 0

Servo and purge pipes checked and hold vacuum. I did check MAP and throttle body in august and reseated them with RTV sealant. TB and EGR adaptations done and OK Aug. Cam belts and tensioners look OK although they are due for a change.

Codes deleted and haven't returned.

I'm at a loss. These engines seem ultra sensitive to and suggestion of unmetered air getting through the engine.

The block breather has a wire going to it suggesting it is controlled by the ECU. MAP is original. Can I test either with VCDS?

What else???? Car really is being a pain.

[sepulchrave]

Have you cleaned out the block breather labyrinth, just blow through it for now to blow all the gunk back into the sump and check it's actually clear.

You can also clean out the MAP sensor with a squirt of contact cleaner in case it's gunked up.

[Breezy_Pete]

Wires to the block breather are just a heating element to prevent it clogging with ice during warm-up in arctic conditions.

Something makes me think EGR valve sticking open, try giving it a tap if you get this fault again.

[LB123]

Had the inlet manifold and crankcase breather off last year and cleaned both. New pierburg EGR then as well.

Will give the crankcase breather a blast. Then clout the EGR and do an adaptation which should check it's working.

Thinking about a new OE MAP sensor but not convinced its duff. Did clean it in August.

Then I think its taking a sledge hammer to the whole car! Really is getting to be a pain.

[sepulchrave]

24 minutes ago, LB123 said:

Had the inlet manifold and crankcase breather off last year and cleaned both. New pierburg EGR then as well.

Will give the crankcase breather a blast. Then clout the EGR and do an adaptation which should check it's working.

Thinking about a new OE MAP sensor but not convinced its duff. Did clean it in August.

Then I think its taking a sledge hammer to the whole car! Really is getting to be a pain.

 

In that case it may be an intermittent wiring issue, the wiring becomes brittle with age and can fatigue and fray internally, very tricky to diagnose but I would start by looking at the MAP sensor wiring since it's the only sensor responsible for originating these codes.

[Breezy_Pete]

Can't see it being EGR if new.

Can you log MAP sensor data (pressure and temperature) with VCDS?

 

 

Edited 5 October, 2018 by Wino

[LB123]

Wiring to MAP looks good but will strip a bit more of the loom to check. Will do a log of MAP & CTS tomorrow.

Thanks for the ongoing help. Past threads, https://www.briskoda.net/forums/topic/454924-evap-emissions-test/?tab=comments#comment-5111253

and https://www.briskoda.net/forums/topic/437485-egr-adaptation-fail/

Edited 5 October, 2018 by LB123

[Breezy_Pete]

Intake air temp, not coolant temp. Sensor is combined with MAP in same 4-pin module.

[LB123]

OK

[LB123]

Hmm. I don't know what I'm doing. Log for how long, when driving, idling, reving on the drive or what???

This was on the drive, up to temperature, and a couple of dabs on the accel pedal.

Has this shown anything or should I do some defined routine?

[Breezy_Pete]

I'll see if I can find something to compare with from my logs. At first glance the pressure reading seems to jump about more than I'd expect.

[LB123]

Did seem to leap around. Snap throttle produced momentary drop to 700+. VCDS gives 200 to 420 as the range but I assume that would be for steady states? Or maybe it should never go outside that range and it does both below and above. Might be time for a new sensor but they are not cheap and I would take your advice on that.

Temp sensor matched CTS when cold and did sensible things so that part is fine.

Edited 6 October, 2018 by LB123

[Breezy_Pete]

I think that range would be for idle. Mine sits pretty solid at 300mbar at idle when fully warmed up.

Can you get another data set where you just leave it idling for a few minutes?

I didn't look closely before I posted about it jumping around; the rpm is changing a lot at the same time, so you'd expect pressure change, is that all you on the go pedal though, or is the engine speed moving about on its own?

[LB123]

All me. Idles at a steady 680 when hot. I will do an idle log.

 

[Breezy_Pete]

Here's a snapshot of the last bit of a 10 minute journey in July, looks like I left it idling for a few seconds just before I stopped logging.

 

[LB123]

I note it did report 459 probably while accelerating so going outside limits briefly is probably OK. Pretty sure mine will look much the same ruling out the MAP sensor.

[LB123]

There's a minute of idle. Did a quick TB & EGR adaptation which didn't make any difference to the figures.

[Breezy_Pete]

Only other thing I can think to try is waggling hoses about while logging. Servo vac pipe, breather outlet pipe, purge valve pipes. See if you can correlate any such activity with pressure changes.

[LB123]

Quote

Only other thing I can think to try is waggling hoses about while logging. Servo vac pipe,........................, purge valve pipes.

Both hold vacuum for five minutes pulled off the back of the carb and attached to a mityvac. Also confirms servo diaphragm and oneway valve are good. Will test then again with more vigorous waggling but I know they are good.

 

The car has had recurrent EGR, inlet leak codes with engine light mostly on for over a year with very little effect on its drivability. Finally found an air leak in the servo hose and fixed it 4 weeks ago. Then after a month of no problems, 6 days ago I got CEL/Engine light/Hunting and undrivable after a restart at Tesco. Five minuters later and two restarts the CEL went out and it drove home fine. Baffling. Deleted the codes next morning and its still fine and code free.

Edited 6 October, 2018 by LB123

[LB123]

Crankcase breather is fine. If I block the throttlebody end of it, oil filler cap in place and apply vacuum to the camcover vent the engine holds vacuum! So no leak there.

I can only conclude the MAP or throttlebody are faulty in some way. Might try the local scrappies for replacements.

Sods law. The car of course is running fine with no faults showing.  Thanks for all the help even if it has only managed to rule out stuff.

[LB123]

Tuesday evening it happened again.

Warm start.

EPC light.

Check engine light.

Hunting. RPM 1100 to 1300.

This time I found the accelerator pedal did nothing even when floored.

Also for the first time noticed the ASR light was also on.

 

Did a few restarts and after five minutes just the check engine light and the car drove fine.

Same set of fault codes.17961,17912,18265, 01314.

[sepulchrave]

Intermittent faults like yours are generally related to wiring loom issues as I said earlier, the wires fray internally so there is no evidence externally of the problem, you have to test them end to end and wiggle the loom to find the faulty conductor.

[Breezy_Pete]

May be worth checking those that go to the TB as well as the MAP/Intake temp sensors. Can offer pin number info if reqd, main PITA is the cage round the ECU, if still present on your car.

[LB123]

MAP/temp/TB wires checked already. I will investigate at the ECU and the throttle pedal.

Wino if you could post ecu pin numbers functions that would be a great help. Thanks.

[Breezy_Pete]

Will look up now.