4 replies to this topic

[jonasbgolf]

Hi Guys,

 

First of all - yes, i have checked just about everything on the vacuum system but it seems as i've missed something on my way to this point.

 

Problem is my MAP sensor reading is low, when engine is idling. My MAP reading says around 50-52 kPa. (Should be 30kPa)

 

Vacuum pipes, is in good working order. 

Charcoal Canister checked

Fuel Trap checked

ECU has been opened up, and the small connecting pipe from outside the ECU to MAP sensor is also in good working order.

Brake master cylinder has been checked (2 gaskets at the front of the round plate).

 

Is there anything else, anywhere else i can check of there is a leak.

Could my vacuum pipes be too small in diameter, to let the "suction" in to the MAP sensor?

 

by the way, yes i have the SP ACR4 code reader to monitor anything i should on the engine. 

Engine is 1293, 270 cam, 1.5 roller rockers, slightly modified head.

 

Best regards,

Jonas (Denmark)

[FlyingScot]

Don't check pipes and fuel trap, just bin them unless they are brand new, the cracks and splits are too small to see normally.
Clean and dry out MAP sensor by placing in a warm cupboard port down and use a piece of cotton string to draw out any fuel residue from the port. check port itself for cracking/splits.

Block all the other connections to the Spi unit (emissions, brake servo etc) to try and eliminate any odd leakage and recheck MAP reading.

What we don't know is whether the MAP read correctly before, it could be the sensor is U/S

FS

[Fast Ivan]

what problems is this giving you?

and what does the sensor read when you rev the engine?

[jonasbgolf]

My problem is a sort of backfire/stalling under light load. When im driving with 2500rpms and lifting the throttle a bit, the engine splutters/Kangaroos (sometimes slightly, sometimes almost violently) but when i put the pedal to the metal, it pulls sort of okay. I've read that when the MAP pressure is off, the ECU sets back the timing and correct me if im wrong - but it seems as my engines timing is off when experiencing these symptoms.

 

Im going to do like FlyingScot has suggested - block of all other connections so that the map pressure readings i will get, is the result of only the thin lines and none of the other pressurised parts like brakes, emissions, etc.

 

I can't remember what the map readings is when i rev the engine, but i know for sure that it does react (If thats a point). 

 

Thanks again for keeping this thread alive - and my hope!!!

/Jonas

[jonasbgolf]

I have just tried to block of the line to the charcoal canister and to the brake servo. (Look at the links for photos highlighting where i blocked the pipes).

 

https://www.dropbox.... 02 42.jpg?dl=0

(The line for charcoal canister, from manifold)

 

https://www.dropbox.... 03 05.jpg?dl=0

(The brake servo stud i blocked)

 

 

https://www.dropbox.... 03 25.jpg?dl=0

(Blocked the line for the air-filter-casing, also.)

 

I even tried to wiggle the plastic adapter at the ecu to make sure it didn't change the MAP reading when i did so.

But nothing of the 3 things above did anything to resolve the low map pressure. (Still 50-52 kPa).

 

Where else can/should i try to block off?