I've posted a few times on here about a stalling issue with. No code but just today at a light with the clutch in and in first it started to bog and sputter and the ses light came on and when I took off I had a severe loss of power. Same thing has been happening for a while and it sputters and dies unless given gas. I got home and read the code with my fancy paperclip scanner and got only one code: 33 since my bird is a 1991 tpi wouldn't it be the map sensor or what else could it be? How would I test the map sensor? Fuel pressure is good and I just replaced the idle air control valve and set it. Thank you for any answers!

 

test the 5v reference voltage and feedback voltage based on altitude.

 

http://www.robietherobot.com/storm/mapsensor.htm

 

Thanks for the reply, if I get bad voltage on the map and I replace the map, and it's still bad how do I test for bad vacuume or relay? Also do I unplug the map for the test or do I jump the wires?

 

If you check 5v reference unplug the map connector.
if you testing voltage based off altitude koeo backprobe the map.
could be map, faulty ecm or low compression.

 

am I probing the map itself or the connector? has a new ecm and it runs perfect 60% of the time so wouldn't a compression issue be all the time?

 

Both

 

Okay, I did the test by jumping the middle wire with the map plugged in. Set my multimeter and tested it on the battery, works fine. I tested the jumped wire with the negative clipped to the negative battery terminal and turned the key to the on position. No voltage. Checked multiple times I had good connections and tried it with and without the vacuume line. No voltage. Does that means my map sensor is fried? And if so would that cause the issue all the time or intermittently? Because the ses only came on once and it only has idle issues after about 15 min of city driving.

 

Also, how would I probe for ground? I found a guide but it is vague with no pictures and is also vague about how not to fry the pcm. Any ideas?

 

No voltage on the grey wire key on when backprobed ?

 

whoops, I probed the middle wire because I used a guide I found. I'll prove the c or gray wire tomorrow.

 

Okay, I have a solid 5 volts on the gray wire but does that mean my map sensor is fine? Would that mean I have a vacuume leak? Cause my idle issue is still there and that doesn't solve the code 33

 

The 5v ref is good how about the light green and what’s your elevation?

 

isn't the light green the signal wire? I didn't know that was part of the test. And I wouldn't know how and my elevation is 800 ft above sea level. So would that leave low vacuume? And how would I test for bad vacuume?

 

investing in a service manual would be good. yes the light green is signal

 

 

I will try to use this diagram, but I'm having some issues using tuner pro rt to retrieve data. Also i have a Chilton's and Haynes manual what is this diagram from? I couldn't find anything in mine. And tuner pro rt isn't displaying gauges for some reason after I load the adx file and without gauges I can't see what my car is doing.

 

Get a helm manual Hayes and chiton are worthless.

 

thanks! I've been wondering why they never give me the info I need. Also can you send the section the right tree of the flow chart mentions? My problem is intermittent and usually has no issue on start up.

 

so I went on helm's website and they don't make a shop manual for my car. The closest one is for a 1989 firebird but not a 1990 or 1991 and they switched from maf to map in 1990. Where did you get yours?

 

As an alternative to the Helm's manual: there are almost always used factory service manuals for sale on EBay. Just do a search for 1991 firebird service manual. Usually around $35.

 

This is the voltage coming off the middle wire while running to check for good vacuume to map sensor. Do these voltages look good for idle and revving up to 3k?https://photos.app.goo.gl/pFKraednsXooz5PRA
Altitude is 800ft and first voltage is with key on.