Bizzo Posted October 9, 2003 Report Share Posted October 9, 2003 :cuss: Ok so I bought the car a week ago and today the alternator goes bad....no big deal i've changed a few alternators before. So i take the old one out bring it down have them test it and it was putting out like 11 volts...so i buy a lifetime warranty one and go home to install it...start installing it and realize now would be a good time to change the back 3 plugs and wires...since my cousin changed the front but never did the back...so i change the plugs and wires...get the alternator in...and fire her up. The car started right up but then sputtered revved to 2k rpm's and the dropped down and kept fluctuating between 200-800. At first I figured it needed an idle relearn so I did that and it helped to stablize the idle somewhat. I then noticed the service engine soon light was on so i shut it off and started it back up. This time it reved to 2500 rpms then dropped down to 200 and died. Started it up and it tried to die again but i gave it some gas and it stayed running at around 1000 rpm but was running rough, then it smoothed out and the light came on again. Oh yeah, I forgot to mention it only stalls when it is in drive. Any ideas? Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted October 9, 2003 Report Share Posted October 9, 2003 How come you haven't got the OBD codes yet?? Check the codes 1st, then re-post. You may have dis-lodged the MAP Sensor vacuum hose because the MAP Sensor is RIGHT in the area where you would have been working... But check the damn CODES! Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted October 9, 2003 Report Share Posted October 9, 2003 How come you haven't got the OBD codes yet?? Check the codes 1st, then re-post. You may have dis-lodged the MAP Sensor vacuum hose because the MAP Sensor is RIGHT in the area where you would have been working... But check the damn CODES! Yeah, I broke my MAP line changing the back three plugs before. And, since you would then have a vacuum leak, AND no way for the ECM to know how to deliver fuel, the symptoms you said make sense Quote Link to comment Share on other sites More sharing options...
Bizzo Posted October 9, 2003 Author Report Share Posted October 9, 2003 The only code stored in the computer was code 33 which is MAP sensor low-vacuum. Can someone tell me exactly where on the 3.1 the map sensor is and where any vacuums line run, so I can try and pin this down. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted October 9, 2003 Report Share Posted October 9, 2003 The only code stored in the computer was code 33 which is MAP sensor low-vacuum. Can someone tell me exactly where on the 3.1 the map sensor is and where any vacuums line run, so I can try and pin this down. Alright. The MAP sensor is attached to a bracke that is held onto the back of the plenum by two bolts. The MAP has one vacuum line and one electrical connector going into it. The MAP is how the ECM determines how much fuel to deliver. It measure engine vacuum, and from that it sends a voltage to the ECM to tell it how much fuel to deliver based on the engines vacuum Quote Link to comment Share on other sites More sharing options...
Bizzo Posted October 9, 2003 Author Report Share Posted October 9, 2003 Ok i'm gonna go double check the connections and make sure they are good. If they aren't does that mean the sensor itself has gone bad? Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted October 9, 2003 Report Share Posted October 9, 2003 Ok i'm gonna go double check the connections and make sure they are good. If they aren't does that mean the sensor itself has gone bad? No, more than likely you broke the vacuum line going to the MAP Quote Link to comment Share on other sites More sharing options...
Bizzo Posted October 9, 2003 Author Report Share Posted October 9, 2003 Yep the stupid vacuum line to the map sensor was off...reconnected it fire it up and it's running good and the SES light is off. Thanks guys for the help. Next I will investigate the TPS because it has a little hestitation when i'm taking off from a stop. Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted October 10, 2003 Report Share Posted October 10, 2003 Yep the stupid vacuum line to the map sensor was off...reconnected it fire it up and it's running good and the SES light is off. Thanks guys for the help. Next I will investigate the TPS because it has a little hestitation when i'm taking off from a stop. if you look at/remove your throttle body(you don't have to remove it to see it....check the inside and make sure the throttle plate is fully closing, lots of times it won't due to carbon build up in the intake and oil residue coming from the pcv system...running a can of GM top end cleaner through the car helps(the 60degreeV6 website probably still has the info on how to do the top end cleaner)or just spray some carb cleaner into the throttle body(it's recommended to remove it first and remove the sensors as the IAC I know shouldn't be cleaned w/ anything due to it's special coating)...you can check the TPS if you have a DMM/DVOM(digital multimeter/ohm meter)..this will tell you if it's receiving proper voltage, you should have a dark blue wire, a gray wire, and a black wire...the gray wire is the reference voltage signal from the ECM which should be ~5volts, the dark blue is the input for the TPS, and the black is the ground...put the postive lead on the multimeter(if you have some smaller pins to attach, they would come in handy) into the signal/input line(the dark blue wire), insert the negative lead into the pin for the ground(black wire), then turn the key to the "run" position but do not crank the car...then manually open and close the throttle plate and observe the voltage to see if it changes(your multimeter should be set to DC voltage)it should go from around ~.2volts(closed) to ~5 volts(fully opened)..after that you can test the reference voltage from the ECM by removing the connections you've made already, disconnecting the connector/harness from the TPS sensor and then insert the postive lead into the pin for the gray wire, simply touch the ground lead on the multimeter to a good chassis ground or to the engine block....It should at least show you that everything is working, if it is causing a slight hesitation you likely can't diagnose that w/ a DMM/DVOM..a lab oscilloscope(visual voltmeter) is needed to show you variations in voltage at a smaller interval in time that wouldn't be detectable by a digital or analog multimeter....anyways, hope this helps Quote Link to comment Share on other sites More sharing options...
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