MS woes

[323driver]

So, saturday, the map sensor in my MS crapped out, it's now always reading a constant pressure, between 100 and 150 kpa. I was wondering why my car was soo lumpy and I had major backfires, I hope I didn't wash the cylinder walls with gas... anyone heard about that happening before?

[therieldeal]

never heard of that

did you try replacing the vacuum line?

[Lex]

Check the vacuum line first. Does it read 100 with the engine off?

[323driver]

It reads 117 on the table in my room with nothing connected to it, just power and gnd. I'm trying to find that thing locally but no one has it.

[Lex]

That doesn't sound right. I wonder if there is a soldering problem? Have you opened it up?

[323driver]

I checked the specs for the MPX and it only uses 3 pins, power, gnd and signal. it has power and gnd as it should, the signal is an output obviously. I'll order another one install it remotely in the engine bay with 3 wires running from the sensor to the MS. I think it broke because of me pulling the vacuum line all the time at -15 (rubber is really hard at that temp).

[Shades]

That doesn't sound right. I wonder if there is a soldering problem? Have you opened it up?

Yeah have you opened it up and does it look like this?... Click Here!

[323driver]

^^ LOL. no, it doesn't look like this, I've built it myself and I know electronics well.

[therieldeal]

suggestion....

i took a short piece of vac hose and "permanently" attached it to the map sensor with a zip tie. then i used a plastic vac line coupler to connect to the rest of the hose. that way i can take the MS out without having to put any stress on the sensor.

[Lex]

I checked the specs for the MPX and it only uses 3 pins, power, gnd and signal. it has power and gnd as it should, the signal is an output obviously. I'll order another one install it remotely in the engine bay with 3 wires running from the sensor to the MS. I think it broke because of me pulling the vacuum line all the time at -15 (rubber is really hard at that temp).

I'd like to suggest against having it in the engine bay due to a few reasons:

1. The temperature characteristics are not friendly. Yes it is rated from -40 to 125 deg C, but you don't want to be close to those values because error becomes worse over 85 deg C.

2. There is no good way to mount it or protect it - it is meant to go on a PCB.

3. It may introduce some unwanted noise in the signal - the engine bay is not an electrically friendly place.

If you prefer an engine bay automotive grade sensor, getting an RX-7 or similar 3 bar map sensor from the yard might be a better option.

[323driver]

Thanks. I really want to use an external one though, I don't like the vac line going to the cabin. The GM 3 bar MAP looks tempting and it's meant to go under the hood.