MAP sensor ?

[Ttype83]

I've been running rich and after looking at just about everything else(reset TPS to .67 volts), I decided to check the MAP(it's only 1 1/2 years old.
I did Freddie's suck test on it and nothing.....no change in idle.
Is there a fuse for this?????
Jim

 

[b4black]

There's no fuse for the MAP. You were in closed loop right? It ignores the MAP when open loop.

This is when a scan tool is helpful.

The MAP should have an orange connector (key) in it, not blue.

 

[Ttype83]

Yes I made sure that it was warmed up first, I retested again after driving home with same results

Yes it has the orange connector.

I tested the MAP with a volt meter

Idle A ground B .92volts C 5.24volts

car off key on a ground B .001 volts C 5.24volts

OK now if the other MAP(1 Bar) that is in the car is bad will it cause this condition?

Jim

 

[b4black]

The orange MAP should vary from 0 to 5V with 0 psi in the middle (~2.5V). With the volt meter hooked up, you should be able to make it change by sucking/blowing on the port.

The BARO sensor under the dash is identical to a MAP. It's blue, like a non-turbo's MAP. 0 psi is at 5V (it can't measure positive pressure). You can remove the blue key and connect it to the MAP harness to check it while you have the volt meter hooked up.

Orange MAP readings should be roughly ½ the BARO readings, since the MAP uses twice the scale (high vacuum - high pressure vs high vacuum - zero vacuum)

The ECM uses the BARO reading as a baseline to compared the MAP to. This compensates for altitude and changes in barometric pressure.

Your idle sounds right to me. High vacuum, low voltage. The key on/engine off should be higher. 0 psi should be about 2.5V. It appears your MAP is blown Try hooking up the BARO (blue) and see if it reads ~5V.


And after I typed all this out, I remembered I wrote this up before and put it on the website:

1981-1983 MAP and BARO SENSORS - On a NA engine, the MAP and BARO are actually two sensors, but the are the same. Both are 1 bar, blue units. With the engine off, they will read the same. (The BARO is located near the ECM and has no hose connected to it). On a turbo V6, they will not read the same. 0 vacuum is full scale on the NA MAP and BARO, but mid scale on the Turbo MAP. This is because the Turbo MAP needs to go above 0 vacuum (aka boost).

With my OTC scan tool I get
BARO: 100 kPa or 4.70 V (full scale)
MAP Off: 52 kPA or 2.34 V
MAP idle: 26 kPa or 0.68 V
MAP 2 psi: 62 kPa or 2.70 V
(The MAP at 15 psi would be full scale 100 kPA or 5.00 V)

BARO and MAP off pressures are the same ambient air pressure, but different scale, so the Turbo V6 scale is off by a factor of two, because it's a 2 bar sensor (or 200 kPa). 52 x 2 = ~100.

 

[Ttype83]

I did some more poking around yesterday and this morning.
I retested the sensor after making sure that the temp was above 160 deg....I also disconnected the battery and checked the ECM connections(first) When I retested
idle A ground B 1.04volts C 5.24volts
off/key on A ground B 2.38 volts B 5.24volts
idle/suck/blowning thru tube B 2.45 volts (that's the hardest I could blown) sucking I could only get it down to .86 volts

OK so it works...humm..I think that I'm not getting to closed loop with the cooler weather now during normal driving.

Why doesn't C change in volts????
Oh I got water under the coil cleaning the old oil/grease stains

 

[b4black]

C is the power or source volatge. It's this volatge that is lowered by the sensor to produce the signal volatge at B. No C, no B.

 

[Ttype83]

Oh now I see......
I think that I need to get a higher temp for the winter.....
Now I have a darn vac leak some were again.....wouldn't you know it, just in time for the BOP race here.....Well I'll hope for the best and try and find it before 8th Nov...
I'm still working on the WOT rich problem too..
If not I can run up to 7 psi, but nothing over..That should be enough to get me into the 15's maybe.

Rich didn't you something on home made knock & A/F guages?
Thanks
Jim