A little off topic, but I think I would have better luck getting help from the folks around here.
I know guy who is having some idle problems with his 1986 Monte Carlo, 4.3L TBI V6, automatic.

We hooked my laptop up to the ALDL connector and fired up WinALDL to take a look at the sensor readings.
When you start the car in Park, it idles around 1000-1100 RPM.
When you put the transmission in Drive and hold the brake, the engine speed comes down to, oh, 600RPM initialy. After a few seconds, the engine speed begins to climb up to 1500RPM-2000RPM, and the car really wants to go. If you put the car back in park, idle speed stays high, and will come down some if you hit the gas and let off right away. During the whole process, the MAP reading is always at 0.0 volts, around 10-13 kpa. I think it might be the MAP that is causing problems. Although, we did disconnect the MAP vacuum line and connected a hand vacuum pump to it. Initially it read 98 kpa or so, and would come down about 20 kpa with each squeeze of the pump. It would eventually reach 0 volts (10-13kpa) and stay there - there was one point where it did seem to not be responding, but I was not running the pump, I was just watching the display. Also, the ECM is complaining about a code 34 ("MAP sensor signal voltage was too low (high vacuum) when engine speed was over 1200 RPM, or the throttle angle was above 21% when engine speed was over 1200 RPM" according to the BAT Auto Tech code list) - which I suppose I can understand this code if the MAP is always reading 0 volts when connected to the engine.

We have replaced the TPS (it was reading 2.9v at zero-throttle and could not be adjusted down) and cleaned the IAC pintle and passage.

Anyhow, any ideas? I am leaning towards MAP sensor needs replaced - just want to be sure I've got the right ideas.

Also, while I am thinking about it, what are normal MAP readings for certain RPM ranges? Should the MAP be reading high or low voltage at idle? (low voltage equaling high vacuum) High or low at 2000RPM? High or low at WOT?

Thanks!

 

Not that I know much about MAP, but if the computer threw code 34, have you tried another MAP sensor? Have you tested the wires at the MAP sensor to see if it's not the wiring? I don't have a chart for the MAP sensor, though...

Oh, hey, woah, I wonder if I can use the info from my dad's former '87 Oldsmobile GM service manual. He got rid of the car but I think he kept the GM book. Maybe that has a chart in it... I'll let you know.

You made the ALDL cable? Cool! Hey which diagram did you follow? Thanks!

 

Been bouncing things around in my head about this off and on today, and I am really thinking it is most likely the MAP. Don't have another MAP sensor to use for testing, but I've got a friend who has a 1987 Blazer with a 2.8L V6 TBI that uses MAP - I am betting it is the same MAP sensor since the TBI is pretty close (actually my friend was with me last night when we were working on the Monte Carlo and he said that the TBI was the same - something about it being a "TBI 400" vs a "200"). Didn't test the wiring - storm was coming last night. When the MAP is totally disconnected, the car behaves the same.

Yeah, built the cable as soon as I found out about WinALDL last month. Used this diagram right here:
http://w1.601.telia.com/~u60113744/s.../aldlcable.htm
Used the MPS2222A transistor from Radio Shack. And instead of connecting the 10k R3 resistor between A & B RIGHT AT the ALDL, I soldered one end of the resistor to the joint of Pin5 and the transistor's emitter (effectively connecting one side to the wire coming from A or "GND" from the ALDL) and soldered the other end to a wire to plug into B on the ALDL. That way I could put all the resistors and transistor inside the DB9 connector housing and just plug the three wires into the ALDL connector.

So far is has come it pretty handy for troubleshooting and it's just neat to see the data rolling by.

 

Hey, thanks for the link! I think I'll go home and raid the old parts drawers. I know I have about a million 2n2222 transistors, I remember buying a crapload from allelectronics.com (before the internet ever existed)... and if i don't have those resistors at home, I deserve to be shot. So the cable just pokes into the ALDL connector? Good, that means I don't have to buy anything. Hey, I wonder if a regular DB9 could be tapped into the back of the ALDL on the car, and screwed down to the underside of the dash, to allow for a regular M-F Db9 cable? That'd make the connection a heck of a lot more secure! Then maybe the actual electronics could be put into a M-F connector box, like a null modem. So that would mean the DB9 cable should be straight thru. Good thing the fiance' is working tonight... But oh man, I haven't seen my workbench in years Gotta start digging.

And yep, looks like you're right, according to both acdelco.com and partsamerica.com. Both the monte carlo (4.3 vin Z) and the s10 blazer (2.8l vin R) share the same part # for the MAP.

86 monte carlo, 4.3l 262ci vin z
ac delco, 213-185 (acdelco.com)
gp sorenson, 779-11502 (partsamerica.com)
niehoff ignition, fe1602 (partsamerica.com)

87 s10 blazer, 2.8l 173ci vin r
ac delco, 213-185 (acdelco.com)
gp sorenson, 779-11502 (partsamerica.com)
niehoff ignition, fe1602 (partsamerica.com)

I'll see if I can come up with a diagnostic chart tonight. Actually, I wonder if the 2.5l TBI diagrams in my '86 Helms book would help. Lets see...

Yep, acdelco.com says the 2.5l TBI I-4 in the '86 Firebird uses MAP #213-185. I'll type up that diagnostic chart tonight for ya.

 

Hmmmm....I like the DB9 idea, lot easier than trying to connect 3 wires everytime and make sure they don't fall out.

Thanks for doing the part search, I don't know why I never thought of doing that!

About the diagnostic chart:
I've got a Chilton manual for the my Camaros and it has a code 34 chart for the 2.5L engine. I will give it a spin. Actually, looks like the 3.1L V6 Camaros used the same MAP as well, my book has a diag chart for that engine too...hmmm...it is a little bit different though, needs a scan tool about half way through. I think I will try the 2.5L chart first. Anyhow, hopefully I can save you the trouble of having to type so much like you did for the other charts you have posted (BTW, thanks! - I saved a copy of 'em so I have them when I need them). I think the first thing I will do is grab the MAP off of the Blazer for testing, then go through the chart if the MAP swap + ECM reset doesn't help.

Thanks for the help Tom!

 

Hehe, no problem, that's how I find most of my performance 2.8/3.1 parts. For instance, the ignition modules... 2.8/3.1 and 5.0/5.7 both use the same GM module for computer controlled remote HEI (8 pin module). The Holley 891-103 and the Accel modules meant for a remote HEI 5.0/5.7 TPI should therefore work with our 2.8/3.1 motors with remote HEI. (Whew)

How'd the 2.5 chart go? Did it fix the problem, or should I put up the 34 chart from my book?

I was going to make the cable this weekend, but couldn't dig up a db9 without cleaning the basement! Got me thinking, though- ever try one of those DOS based ECM readers? The two laptops I have are very old ('95) Dell 386sx16's... no way they could run Win95 for WinALDL. They probably don't have more than 640k of memory! Er, well, maybe they do; they can run Win3.1.

 

They do. I am using the Holley 891-103 in my '89 RS.

Sorry I didn't update you.
I called the guy about the car the last Thursday and he said that he drove it to work that day and disconnected the battery for the day. Came out after work, reconnected it (ECM should be good a clear by then!) and it has been running fine ever since. The only thing that was every replaced was the TPS, and I don't remember whether or not he reset the ECM when we replaced it. Code 34 seems to have quite occuring as well. Guess it wasn't the MAP.

No, I haven't. What ones are you thinking about, I'd be interested in trying 'em out.

 

I'll see if I can hunt 'em up, I forgot about my bookmark file when I went from Netscape to IE. I think I have a copy of my bookmarks saved -somewhere-, but I'll probably never find 'em.

 

Here's the only one I could find quickly, it was from the prom burning for beginners article (by traxion): http://moates.net/gmecm/software.html There's a few cable diagrams there, too!