Z20LET boost/running issues

[Turbodave]

Gents, would appreciate some input here. I've had a look through some historic posts about this and being fair, there seems to be a bit of conflicting information so I'm a bit unsure/fed up now!

CAR
2003 Astra GSi turbo with 70,000 miles - standard bar a remap, however we have checked the map and it bears no significance as the car has been doing this prior to it being mapped.

SYMPTOMS
Hestitant under boost and when maintaining contsant speed on the motorway. Can power through hestitancy although occasionally emission light will illuminate and restrict power. However when the light is on, the car drives alot smoother all be it with little or no boost.

When the emission light is on, disconnecting the multiplug at the boost sensor has little or no effect on the car... whether this has any relevance, I don't know. Likewise, I can disconnect the ECU which clears the light and returns the car to full boost, all be it very hestitant and surges.

Additionally, the car suffered coolant gauge issues. It'd regulary read cold or drop out for no reason. I changed the sensor and although the car now runs a constant temperature, it runs around 80deg despite having a 92deg thermostat. Could this perhaps be related to the common earth issue too?

FAULT CODE
Vauxhall dealer check and found P1106 stored relating to boost sensor or similar and immediately decided the boost sensor on top of the intercooler was defective.

SO FAR
I've declined the boost sensor at present, done some research and found the technical field remedy for the poor earth. On Saturday I removed the battery and tray and went searching for said earth connection (4 earths, crimped and onto block) however for the life of me cannot find said connections? Anybody have a picture/diagram to hand?

The only earth I can see on the injector loom is the two wires bolted to the side of the inlet manifold. I traced these back and it appears one buggers off along by the injectors and the other is for the coil pack. There is another but its unclear where it goes although apprars to enter the loom and disappear down towards the battery.

On advice from those in the know, it could be either a faulty boost sensor on top of the intercooler, a faulty boost control solenoid/amal valave, mass air flow meter or the wiring issues. My local dealer knows nothing about the latter.

FINALLY
The car is due back into Vauxhall on Wednesday to recheck what has been done, truth be told I think I'm wasting my time. It has been suggested I change the mass air flow meter and boost sensor to elimnate them, however unless somebody is local and willing to let me try theirs for a quick roadtest... that's not really viable.

Anybody experienced this before, or willing/able to assist in excahnge for some beers and worldwide gratitude and fame. Perhaps.

Cheers

[fennyLET]

Cant find P1106 but ive got P0106 witch is Map Sensor. (air leak, Naf sensor or wireing)

[Turbodave]

I know the code relates to the map/boost sensor... but there's more to it than that, hence the earthing issues and more to the point, where is said earthing issue as nobody seems to have the answer!

[Pom]

Suspect Airflow meter is faulty, defo worth tyring

[cavbow]

Had similar fault on my Zafira after searching a few web site i was told to change the sensor on top of the turbo and the 1 on the back of the block and touch wood for the last 3 years the problem has never come back

[bert opc]

did u find out problem my act is hesitating too low gears off boost and on boost replaced everything apart from intercooler sensor and ecu

[Turbodave]

Unfortunately not gents, the story continues here:

Z20LET ongoing boost/hesitation/running issues - Astra Sport and Astra Owners Club - Mk1 | Mk2 | Mk3 | Mk4 | Mk5 | Mk6 | Astra Van | 888 | VXR - All Welcome

Airflow meter has been replaced, front boost solenoid has been replaced and the rear has been bypassed.... still the same but click the link for the full story so far, it's compelling and suicidal reading!

Open to suggestions chaps, sick to the back teeth of it now.

[mac1976]

mate had the same problem it turned out to be the coolant temp switch

[Tom Williams]

I know this is C20 LET related but I had a similar issue with my Cav Turbo.

In my case it was the gap in the spark plugs, being a little too big the spark would be blown out by the force of the boost.

Adjusting the gap cured the problem, but like you I had the ECU light on with a fault code that was boost related.

Tom

[Turbodave]

I know this is C20 LET related but I had a similar issue with my Cav Turbo.

In my case it was the gap in the spark plugs, being a little too big the spark would be blown out by the force of the boost.

Adjusting the gap cured the problem, but like you I had the ECU light on with a fault code that was boost related.

Tom

A good point well made sir, it's running NGK Iridiums but on the standard gap so it's possible this is too much. Although given it only stutters under light boost, I'd have expected the plug gap to become more significant at higher boost levels. Certainly willing to try anything at this stage, so will drop the gap a baw hair and see what happens. The C20LET is definately a more simple beast to work on!

mate had the same problem it turned out to be the coolant temp switch

It's been renewed already with a new GM part mate, but cheers

[BazW]

Sorry to bump an old thread but my SRi turbo is doing the same thing...just wonder if you ever sorted it?

It's standard apart from an unknown remap, allegedly done by Courtnay but as they only keep the customer name not the car reg they couldn't tell me if they'd ever worked on the car. Removed the chav valve, replaced the boost control solenoid. It's also got a VXR turbo fitted, bought new in Feb