Hi All,

Symptoms

No Heater "tap not working on firewall
No Trip Computer Data Instant Fuel
No Cruise Control


Replaced Bad Vacuum Hose

Heater working
Instant Fuel Reading on Trip Computer
Cruise controll Holds at 70km\h -80km/h but nothing else


All related or am i mixing issues ?

Regards

Marc

 

The trip computer, unlike the other two, does not rely on engine vacuum in any way so it's the odd man out. The other two might be related.

If all the other t/computer functions seem normal then the fault is likely the t/computer itself. However there IS an "interface" module in the boot that converts ECU data into something the t/computer can understand. Perhaps it's on the fritz?

In either case I don't think there is any diagnostic procedure other than "substitute with known good unit" and see what happens

Others will chime in

Cheers
DD

 

Hi Doug, Since i changed the one hose, i have better response from the engine along with a very nice idle compared to the lumpy one before secondly the cruise was not operative at all prior to the hose change over so i might go grab a vacuum kit and replace the hoses as i think i still have a leak somewhere

Regarding the Trip computer, wouldn't the Module\computer Collect Data like manifold pressure to get its numbers for Instant Fuel usage, if the engine is sucking in more air than it should and the data is erroneous because its fighting Equilibrium wouldn't it confuse the poor trip into a zero reading ?

 

Here's some really good info on cruise control repairs


Cruise Control






The trip computer interface takes vehicle speed readings (from the speedometer transducer) and injector pulse width readings (from the ECU) and somehow....the electronic science is lost on me....calculates fuel usage. Neither the trip computer nor the interface "know" if there's a vacuum leak. They only know distance travelled and how long the injectors stay open (pulse width).

The only thing I can think of (beside an actual fault) that would cause a "zero" miles-per-gallon reading is the engine running but the car not moving. For example, sitting at idle you are getting zero miles per gallon.

If the "average fuel economy" reading seems to function OK but the "instant" does not, I would suspect a fault in the t/computer. If both gave a "zero" reading I'd suspect lack of input from the speedometer circuit.

If the engine had a huge vacuum leak and all sorts of horrible problems BUT it still ran....and the car was moving....and the speedometer circuit was sending a signal...you'd get some sort of reading on the computer. It might be horrible, but it would be more than zero miles per gallon.

Cheers
DD