someone knows the exact idle map voltage ?

XM-V6 · Post by **XM-V6** » 21 Apr 2004, 16:45

Hello,
I am new on this site.[:I]
Does someone know the exact output voltage on the map sensor when the car is idling?
Car is a XM v6 engine year 1998, engine ES9J4
Mine is giving now 1.4 volts at idle wich is I think a little bit too high.
(Sorry if my English is not so well, i am Belgian)
greetings.

alexx · Post by **alexx** » 23 Apr 2004, 11:55

I have only an info about RGY engine (2.0 16v if I remembered correctly), and idle manifold pressure is stated to be 375 mbar. Since MAP sensor has 5V supply and output voltage is in proportion with pressure, voltage should be 1.87 V.

XM-V6 · Post by **XM-V6** » 24 Apr 2004, 17:20

Thanks Alexx,
yesterday I did teh measurement on my peugeot 206 1.1 (it has almost the same type sensor) an came to 1.485 v at idle (cold engine) and 0.8v when decceleration after pushing the throttle at stationairy.
the car runs quite good but i feels more like a 2.0 litre engine than a v6. What can be wrong else ?. The lambda sensor is already replaced by the dealer. By 2100 rpm it feels like the engine shudders above 4000 rpm it pulls like a rocket.

alexx · Post by **alexx** » 26 Apr 2004, 15:41

Well, it's hard to tell. I also have a slight problem with my Xantia (1.8 16v), which didn't show up on the diagnostic device - when I push the throttle quickly, there's a short delay before the engine reacts, and then it reacts abruptly, on off/on fashion. This delay is short (about 1/4 of a second), but a bit disconcerting. I'm planning to check MAP sensor and throttle potentiometer manually, but didn't have a time yet.
About the lambda sensor, when you push the throttle quickly and/or fully, it's input is disregarded anyway, and ECU relies on main fuel and ignition map (manifold pressure vs. rpm).
It would be a good idea to test voltage on the MAP sensor with engine stationary and ignition off also - should be about 4.5 V or above. With engine idling, voltage should also reach near that value on brief throttle kick (on my case, diag. device was showing up to 980 mbar, which I suppose is normal, since there's almost no vacuum at that moment).

XM-V6 · Post by **XM-V6** » 26 Apr 2004, 16:38

When I drive a long down hill traject without pushing the throttle, the mileage never comes under +/- 3.0 litres/100km on the bord computer so I think the fuel cut-off is not working.

alexx · Post by **alexx** » 26 Apr 2004, 18:32

Hm ... Assuming that fuel cut-off is incorporated in ECU (as it's a relatively new car), maybe the problem is in worn throttle potentiometer, so that ECU doesn't know that the throttle is off.
It's not easy to trace this kind of problems.

David Goddard · Post by **David Goddard** » 27 Apr 2004, 02:44

For the ES9J4:
5V feed to the MAP
4V signal from the MAP with engine stopped.
When engine starts it should quite quickly drop to 0.7V
No drop equals faulty sensor.
Or:
4-5.8V at 0 m/bar vacuum
2.5 - 3.7V at 300 m/bar vacuum
1.3 - 2.0 V at 600 m/bar vacuum
Source: Car Mechanics Magazine - February 2000

XM-V6 · Post by **XM-V6** » 27 Apr 2004, 02:59

Thanks David