1997 Civic DX

Never in my entire life has a MAP sensor stumped me like this one. Car runs fine for about 75 miles, then all of a sudden throws map code and runs like garbage (Code 3). Tried 3 different computers, converted to obd1, ran wires directly from pin, tried different map sensors. Pretty much stumped right now. I'll figure this out, but in the mean time any useful tips would be appreciated. The part that gets me is after the car sits for about 4 hours it will run fine again. BTW, the voltage is correct.

 

How is the gasket/seal.

Try running a seperate ground to it.

Try driving it around with the voltmeter attached and see if you see anything unusual like a voltage dropout or something.Maybe a spike.

The ECU is seeing something that has to do with the voltage either none or too much at a certain time.

When is it setting off the CEL? Full throttle or at idle or cruise?

 

THe CEL comes on when the car is cruising, at idle, or at WOT. I checked the voltage as soon as it happend and it was correct. Looking for a voltage spike makes no sense because i tried 3 different computers, with map directly run from the ecu. Idk. I dont think 3 different computers would send a voltage spike, if it does exist. Bump for some more ideas.

 

Directly run to the ECU. You have bypassed the harness then, OK. I was thinking that somewhere in the harness you had a bad connection or something.

We are talking about the map mounted directly to the IM correct?
So different ECU's. wires, and MAP's hmmm. Sorry just thinking...

Let me think about this more and I will see if I can come up with something else.

 

Lol, please do. I'm going to fix this either tomorrow or Sunday and i'll post what was wrong just for future reference, but this is really a mind boggler.

 

I don't have any ideas for you. Booo!

What could be throwing off the map?
Do you have the EVAP can and solenoid hooked up? Maybe during purge it is confusing the MAP?

I'm thinking it's not the MAP but something else. It has to be! Vacuum leak?

 

Yea, im running out of ideas as well. Im thinking that the harness, because it was touched, could have been pined backwards. Sooooo with that said, im running the wires directly to the MAP, but maybe the positions are wrong (from when i got the wrong voltage readings) (and when it fully warms up, it glitches). If you can, can you check for me. Do this with the clip facing up like it is in the picture. I dont need the colors. Just the voltage readings according to the position. Like the middle is ____volts, the right is ____volts, and the left is ____ volts. Lol, long story. Thanks for your help.

 

So you can fully understand what im saying, let me better clarify it. Maybe when i took the original voltage readings, the 3v and the 5v wires on the map were backwards bc the harness was touched by someone. So now i ran the wires directly to the Map from the ECU based on those original voltage readings.

 

You should have 5v on the positive D17 (Supply)
0v on D21 (Ground.)
You can check these 2 with the connector disconnected using battery ground as the black side.
And the signal wire I believe it is the middle one will be varying.
With the engine off the reading will be different with it running.

I don't have a voltmeter here but I can get you the spec's that my books say.

It looks like at idle w/18in.hg. it should read 1.4-1.6v on the signal wire connected to the sensor. And with the motor off it should read 2.7 - 2.9v
This would be with the red connected to the signal wire and the black to -batt.

Hope this helps. Sorry if I simplified it to much.

 

Lol, no i know the voltage at the pins, but maybe i have it wrong on the map end if you get what im saying. On the MAP sensor, i just want to know which position is suppose to recieve which voltage.

 

I don't have your model of MAP sensor My 88 is on the firewall so they are not in the same position.

Find the ground it should be one of the outside pins. Look for continuity between the ground pin and the negitive on the battery.

The other outside pin would be the 5v and the middle pin is the signal or output.

 

GOT IT .....Here it is for anyone who needs this in the future:

 

I new there was a little difference between them now I know.

So it is all fixed? Cool.

 

Turns out it was a bad ecu which was sending the wrong voltage and destroying the MAP. THe voltage was always perfect every test, but it must have spiked at times. Moreover, when i would switch the comps, the MAP was already burnt. Lol, sometimes we overlook the simpliest of problems.