My old IAC was stuck at 160 so i replaced it with a new one. now the counts bounce around between 118 and 160. Im still getting a MAP low code, excessive vacuum. the car does not want to idle with the new IAC installed, however i can get it to idle by manually adjusting the old IAC about half way open but it is rough and about 200 rpm higher than its supposed to be. im now thinking that my map code is causing the pcm to add too much fuel making it bog down at idle but i dont understand my MAP code seeing as datamaster shows MAP KPa at a steady 10.7. can anyone help with any ideas?

 

Are you sure Datamaster is showing 10.7 kPa? That's way below the "normal" value for a stock cam, which will run about 35kPa at idle. 10.7kPa would correspond to a vacuum of about 26-27"Hg, and there's no way an engine can pull that much vacuum. With the cam you list, I'd expect about 45-50kPa at idle, if you have a really good tune. 10.7 kPa would set the code, since I think in the 93's, the code sets when MAP goes below 20kPa.

Are you sure Datamaster isn't reading in "inches of Mercury", because 10.7"Hg might actually make more sense for your car (19-20"Hg vacuum)?

Low MAP/high vacuum would cause the speed-density system to provide too liitle fuel at idle, since it thinks the air entering the cylinders is very thin, and has less mass than it actually does, so it would supply very little fuel.

 

its deffinately showing 10.7KPa, ive done several runs and all of them show the same. MAP sensor and pigtail are new and the wiring checks out fine. im at a loss as to what the problem could be right now.

 

Looking at my manual, DTC 34 sets when the MAP reads less than 14kPa.

Have you verified that the ECM is supplying 5.0V between the gray and black wires at the harness connector? If you have that, measure the voltage between the lt green and black wires with the engine idling. Should be getting something in the range of 1.5-2.0V.

What does DataMaster show as the "barometer" reading? That comes from the MAP sensor as well.

 

barometer is showing a pretty steady 11.1 KPa.

should this be done with the connector pugged in tha MAP sensor or unplugged?

 

Plugged in otherwise how would you get a feedback of less then 5 volts?

 

I was not sure. on the diagnostic aid i have access to it says,

-ignition off
-disconnect electrical connector
-jumper harness terminals B to C
-ignition on
-MAP voltage should read over 4.7 volts, does it?

Ive done all of the checks on this page http://home.comcast.net/~fastbird/Tr...Aids/dtc34.jpg courtesy of fastbird. everything seems to check out.

I haven't measured the voltage between the lt green and black wires with the engine idling yet. I'll get to that sometime today.

 

Barometer (assuming you are near sea level) should be about 100kPa. Your sensor or the wire is definitely screwed up.

Leave the connector on the sensor. Use sharp pins held by the meter's alligator clips to pierce the wires.

 

im seeing 5 volts on on the gray and black wires.

the engine will not run long enough for me to measure the volts between the grn and blk wires. when it fires up it jumps to about 1200 rpm and dies instantly (1-2 seconds between start-up and dying). i had no-one to start the car while i was under the hood.

today i put in a spare MAP sensor i had and it showed the same readings.

i checked continuity from end to end of the grn MAP signal wire, it checks out fine.

if the gray and black wires are supplying the 5 volts as needed would rule them out as being damaged?

 

Yes supply is ok. Keep in mind that a bad MAP sensor should not cause the engine to shut down.

Since you checked continuity of the MAP sensor wire from end to end, unless you have some sort of connector issue, then the only thing left is PCM.

Try this for giggles, jump from the grey wire to the green wire and see what the pressure indicates. Then jump from the black to the green wire. If you are sure about the wire continuity and connection of the green wire if it still doesn't swing you know the PCM is bad.

If you really want to be sure about the PCM, jump directly from the PCM pins instead of at the MAP.

 

Is it possible you crossed the wires when you installed the new MAP pigtail?

You can still check the voltage across the lt green and black wires with the engine not running. Should be at least 4.5V and more likely close to 5V.

 

Ive checked the wires several times, they are connected right. Ive got 5V across the grn and black wires.

I'll try playing with the wires tomorrow to see what i can find out.

 

Just to make this clear.... you measured between the green and the black wires, with the key on, engine not running, and you got 5V? That would correspond to a barometer of 103kPa. Either the signal isn't getting to the PCM, or the PCM is not interpreting the voltage correctly.

 

im sorry, that was a typo. ive got 5V on the gray and black wires with the ignition on, engine not running.

i have not checked the voltage on the green and black wires yet.

thankyou,

 

Then that's what you need to do. The green wire is the signal wire. It will put out ~1.5V at idle, up to 4.8V at WOT and about 4.9-5.0V with key on/engine off, at sea level. You will get less voltage key on/engine off if you live above ea level.