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Hi guys!

Last few days I've been experiencing something weird with my 75 1.8 TB.
The car runs fine, but sometimes boost pressure just dont go over 0,3bar (1,3 on the gauge), and there's no overboost at all.
If I restart the car, it is up again for the fight!

Usually this happens when I cruise at low speeds, or running around on traffic, because if I give it a hard run, pushing the revs high and using all the performance, there are no symptoms of this lack of boost.

I'm think it has something to do with the knock sensor, because if I turn on the switch on the dash board, the lack of boost start as soon as the red light comes on. Tha engine does not knock at all...!!

Any help provided will be most appreciated!!

Regards
Alex

It's a "feature", whenever you just cruise the knock sensor will be activated. I have no idea why but it's really annoying.
Check camchain tension, it might hit the head (yes, I'm serious).

Mats wrote:It's a "feature", whenever you just cruise the knock sensor will be activated. I have no idea why but it's really annoying.
Check camchain tension, it might hit the head (yes, I'm serious).

Thanks Mats!
I checked the chain tension last week, when I checked the valve clearances (which were fine, by the way..)

So all your T really needs is to avoid cruising...

Mats wrote:It's a "feature", whenever you just cruise the knock sensor will be activated. I have no idea why but it's really annoying.
Check camchain tension, it might hit the head (yes, I'm serious).

Can't the knock sensor be simply disconnected and prevent this "feature"?

Sure, but then you won't have that help when you really need it

I'm running on 100oct petrol with std spec engine so knocking won't be a problem, I guess...

Plus, we're studying a way to relocate the sensor to avoid it working when it's not supposed to!

Well, if you relocate the sensor you might as well just disconnect it, it will have the same effect.
The best thing you can do for your 75 T is to remove the std injection system and put an aftermarket system in it's place, the std stuff is pretty much useless.

But then again, your car looks like it is in immaculate factory condition and it would be a shame to destroy it.

Well, I'm not a purist so any mods will be welcome, like trash those ugly "America" bumpers, and stick a Veloce kit in it!!

An aftermarket ECU would be great, but honestly I don't know what kind of budget are we talking about... any idea of values?

After all, the problem is not in the knock sensor but in the butterfly potenciometer.



I've turned the switch in the dash board on, and red the signal it was giving at idle: 4 plus 2 blips. Well, regarding the manual, this signal means there is a problem with the butterfly potenciometer.

Any experience on this problem?

Isnt a screw missing here...?!

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Well, I've replaced the butterfly potentiometer and finally the car runs fine now!!!

Alfa Romeo could not supply this spare part, as they say it's from a very old car!! Nevertheless, they informed me it cost almost €300 when it was available!

But I went to a Bosch Car Center, as that's a Bosch injection system, and a Bosch sensor, and within a week, I had the new sensor fitted in my car! It cost €152, with fitting and calibrating included!

All I can say now is thank you Alfa Romeo for no being able to supply that spare part!!

This is typical of Alfa Romeo's support for their heritage, try getting new headlights for a GTV6 or anything else! Not all car makers are this bad

I probably have a same problem...
Tell me please, which part number is that Bosch TPS?

Thanks

Bosch part number 0 261 211 004.

You have to check the error code given by the led on the dashboard at idle...