Alfa Pages

[johnny]

As I have restored my 33 series 2 of '88, fitting an 1.7IE 8v engine with Bosch Motronic MP3.1 fuel injection, I have noticed, that in traffic when I accelerate, the engine shows hesitation and the car is not accelerating in a continuous rate. On the other hand, on the open road the car runs normally. My mechanic suggested that it is the map sensor that is blocked with dirt from the intake manifold and when I leave my foot from the pedal and then I press it again, the map sensor can't recognise if the engine is working under load. He also recommended of fitting an one-way (I don't know if it is the correct word) valve, after cleaning the sensor, so as not to leave air and dirt from the intake manifold to get into the map sensor. Could anyone please have an advise for such a problem?
Thanks in advance

John

[Admin]

Hi

What your mechanic suggests could be possible but I would not think it is likely. Disconnect the line to the map sensor (built into the ECU on that car) at both ends and clean it out.

I cannot see how a one way valve would work at all. How would the ECU detect changes in inlet air preasure?

The problem you have sounds like a late 33 with that injection system that I drove which was caused by a failed lambda probe.

All the best

Keith

[johnny]

Keith, thanks for your reply. I'll check also the lambda sensor, since I notice high fuel consumption too. What the mechanic says is that dirt is not at the line that connects the map sensor and the manifold, but at the sensor itself and one way valve allows the back pressure of the manifold to be measured by the sensor, but keeps the dirt away from sensor. Anyway, there is something also I would like to know. Since I have not fitted a catalyst does the lambda sensor work well or a catalyst is necessary for the lambda sensor to measure the oxygen content at the exhaust?
All the best

John

[Admin]

Hi

Although a 1 way valve would allow pressure changes through in one direction it would not in the other. For example if manifold pressure dropped then the MAP sensor would also receive air at this lower pressure. However when the pressue increased afterwards the valve would stop the increase in pressure affecting the air that the MAP sensor was measuring.

The lambda probe is before the cat so it should not care about it.

All the best

Keith

[BILL]

Maybe a small fuell filter would be better than the one way valve.Just a thought.