A2 rough idle + no throttle after rebuild

[jonny944cs]

Hello all,
Would love to hear if anybody experience with the following and can offer any suggestions (I am new to this vehicle and VAG COM)?

Engine = 1.4 Petrol - Code AUA

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Chassis Type: 8Z - Audi A2
Scan: 01 02 03 08 15 16 17 37 45 46 56 57 75 76 77
VIN Number: WAUZZZ8Z02N036715
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HISTORY:
- Crank sprocket slipped on the cambelt due to ice formation filling in the tooth profiles => 8 x intake valves bent => no other damage => so, new valves fitted and lightly lapped = > head rebuilt with new gaskets.
- Engine started on the first turn of the key and sounded good for the first 30s or so on the rich startup map => I gently blipped the throttle and the revs rose to 2500rpm => on return to the idle position the engine was now running roughly, with a lumpy hunting idle.
- Fault code scan revealed the following:
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Address 01: Engine
Part No: 036 906 034 Q
Component: MARELLI 4LV 3415
Coding: 00051
Shop #: WSC 00579
WAUZZZ8Z02N036715 AUZ7Z0B2061291
1 Fault Found
17961 - BAROMETRIC/ MANIFOLD PRESSURE SIGNALS – IMPLAUSIBLE CORRELATION
P1553 – 350C
Readiness: 1110 0101
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- So I checked the following:
o Air leaks – Nothing visible (difficult to say for sure) Can anyone recommend a suitable test procedure?
o Cycling through test functions – each part appeared to respond
o Cam timing re-checked, case I’d messed up => all correct
o Compression test = 12bar across all cylinders (test carried out at around 30°C water temp, ECU fuel P fuse removed, foot on the accelerator. I’m not sure how the electronic throttle responds in this condition… anyone?

- No further forward, I decided to check the live data blocks:
o IGNITION ON (revs=0rpm) (MAP=999mb) (Throttle=7.5°) (Ignition=0°)
o ENGINE IDLING (revs=1275rpm) (MAP=675mb) (Throttle=7.4°) (Ignition=0°)
o ENGINE RUNNING + THROTTLE BLIP (revs=1275rpm) (MAP=690mb) (Throttle=7.4°) (Ignition=+/-4°)
- Points to note from live test
o Throttle angle pretty much constant throughout all three tests
o The MAP values seem too high (as expected with the fault code), manual states values should be between 240 and 420mb
o When blipping the throttle, the revs rise only very slightly and the ignition angle is the only parameter that appears to change in response.

- My next thought was to try and clean the TB and perform a re-align.

Thanks in advance

Jonny

[Crasher]

Could be the throttle body. It is a 2002 with an AUA engine for anyone who wants to know.

[kenney]

Check intake manifold pressure sender
Check intake system for leaks (unmetered air)
Check exhaust gas recirculation system:
Check throttle valve control part
Check activated charcoal filter solenoid valve
Try and generate the readiness code,this might show up what is wrong

[jonny944cs]

Hi Crasher, yes it is.

-> the throttle body appears to cycle fine when prompted.

Hi kenny,

Tried all of the your points, the only one I'm not confident about is the un-metered air.

Update: i have just sprayed some brake cleaner at the intake manifold with the engine runing - the revs fluctuated!

I'm about to take the inlet manifold off, hoping to find a kinked or missing seal - wish me luck.

[Crasher]

I had one earlier today with the same fault code and problem on a 1.6 BCB engine (very similar) and the reason was a leak on the servo feed pipe. Even though the TB looks OK, I would still clean and reset it.

[jonny944cs]

Update 2 - Problem Solved - Kinked rubber seal on intake manifold port 4, I must have caught it lowering the head onto the block (see attached image).

Engine now runs sweet as a nut.

Massive sigh of relief.



Thanks for your help guys.