Stalling Cadillac 1994 STS Northstar

94 STS with 85K has given flawless performance for two years. Two weeks ago it stalled and stalled and still does. The engine guns itself to keep up the rpm's while I am at a stop "while I am braking to keep it from running away": It will eventually die unless I can get out on the open road again!  The OBD1 is giving the performance snapshot of codes P032(Eo32) Open MAP Sensor Signal, P071(E071)Intermittent MAP Signal, and P073(E073)Intermittent Coolant Sensor Signal. Where do I go to start looking and checking? Where is the MAP Sensor? Can somebody help me with this problem?


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MAP sensor under intake manifold cover. Check connector at sensor and condition of harness to intake manifold. Coolant sensor is on drivers side of rear head. Check coolant level and sensor connector. Do you have FSM, know how to monitor data with on board or obd I scanner?

Thanks for the fast reply. Sorry for the delay for answering. I do not have a Factory Service Manual (FSM) for the 94 STS. I only have the Chilton's repair manual for 90-98 for the Cadillac illiterate, like me. I can readily scroll through all the funtions of the On Board Diagnostic (OBD1) on the instrument console and get data.  Most of it though,  I don't know what they mean. I have a print out from Anthony Haukap's list of Powertrain codes (PCM) and Engine Control Module (ECM). Am I missing something? Tell me what you want me to know? I'll get into the engine work this weekend. Thanks again!

 
The codes are listed in the FAQ .. write them codes down and see what each one is.
The Factory Service Manual is about the best gift you can get yourself and for $30 or so .. cant beat it.

you can pay as much as $120 if you like, but I get any FSM for around $20 to $40, slightly used.





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MAP is PD02 what does it read at idle and while driving. Coolant sensor is PD04 monitor it also, it should be stable 

MAP is giving 39-40 at idle on the OBD conrol: it ranges from 11 to 60 while warm and test driving. I assume these are kPa's (pressure) or something else.  I haven't gone inside yet to read voltage on the multimeter at the sensor. ALSO; Temperature sensor seems stable and reads 103 on the OBD at the climate control center (CCC). Again, I don't know what 103 is as I have not gone inside yet to read the voltage on a voltage meter. ???  Will send more info as I can get it.

Data is normal - a good thing, dont worry about DVM yet. You looking for a spike up or down.

I mulled over all the advice that has been given and read some more in links and FAQ. Haven't got the Factory Service Manuals yet.  I did get into the engine.  Took off the intake manifold cover and probed around looking and looking for problems.  I only have OBD1 and no scanner so I did not get too far. If I wiggled something to make a spike or an "open" circuit I would not have known about it since the OBD1 is inside the car and not out under the hood where I am.  I have a couple of multi-testers but without proper pigtails I didn't want to use them for testing. I didn't want to break into any of the wiring for the MAP sensor or harness.  Everything I found looked good but very delicate, especially the harness.  I knew I was really getting out of my league of repairs and ability. I put it all back together and have been running it since.  The stumbling and stalling is present especially when it is hot and been run for awhile. 
 
Last night it (the STS) stalled going up a hill at 30mph on a curve in the dark and, there I was trying to start it up with cars coming up behind me without my lights on a blind curve.  It scared me and my pride got down sized a bit. Realized I got to get this situation under control and warmed up an old VW Rabbit I keep for a spare car.
 
Made contact with a not so local shop that specializes in Cadillac service (not a dealer service). I chatted with the owner of the business for a few minutes and somehow feel comfident that I can do business with him and his crew; Also, the local GM service shop here adviced me to take it to a specialist or Cad dealer who has the Caddi manuals and has had experience with that year and some of it's problems. I will take the STS to the specialist guy this week for further diagnosis and repair; if that is what is needed. I will keep you in mind and I will report what they find wrong with my 94 STS Caddi. I'm thinking that besides intermittent MAP sensor failure maybe the EGR valve is stuck open when everything is warmed up? Oh well! More later!

I have a '94 STS and got the same symptoms, random stallings and error codes. Just changed the MAP sensor and all got back to normal.
You can find the MAP sensor online at www.rockauto.com

The curious thing the Cad specialist found was that their scanner would not communicate with the PCM in my 94 STS Northstar and that worried me.  Instead they used my On Board Diagnostic center on the dash to bring up a code for a MAP failure.  The MAP was replaced and most of the symptoms disapeared. After a 40 mile drive they were getting a code for a Trottle Position Sensor failure for idle speed control. The car was really running out of whack now! It tested fine out of the car but when replaced again it was still acting erratic.  It was replaced with a new one.  Still not running right and now a new code for coolant temperature sensor came up so I had it replaced too.  Still not running right with the new TPS and motor, a replacement remanufactured (PCM) Power Control Module was tried.  The R/R of the PCM solved any remaining problems and their scanner was now able to communicate with it.  No new codes came up and the car has run beautiful for the past week. It was pretty expensive diagnostics and repairs but it seems worth the peace of mind of a fine running trouble free Northstar.