MadPSI Posted February 26, 2005 Report Share Posted February 26, 2005 Car: '92 3.1L Cutlass Supreme S... (bone stock, O2 sensor about 2 months old) Had to go to emissions, so I thought that I'd do some routine maintenance on it before I took it in by changing the plugs and wires. The car ran fine beforehand... Totally failed emissions the way it is now, though... Here is what happens now: Cold start-up - Car acts like it's missing, I have to keep my foot in it to keep it running. Sounds like it has a wicked cam in it, which would be a good sound if that were the case. This phenomenon lasts about 30 seconds before the car decides to fire on all cylinders and idles fine at about 500 RPM without any help from the throttle. Driveability: Car acts normal under 25% throttle and WOT. Anywhere in between it lunges erradically, RPMs jump up and down constantly. At 50-75% throttle it's like power, no power, power, no power, power, no power. etc... Almost like the torque converter is slipping randomly, In-drive Idle: Car idles fine sometimes, but most of the time it bounces off the "stalling point" and dies occasionally. No rhyme or reason to what it wants to do next... I've done a few searches and found a bajillion possible causes for this behavior. I'm just hoping that the specific problems that I'm having can be traced to a specific component. TIA, MadPSI Quote Link to comment Share on other sites More sharing options...
Brian P Posted February 26, 2005 Report Share Posted February 26, 2005 Check to be sure you didn't break, crack, loosen a vacuum line at the back of the engine, going to the HVAC system, MAP sensor, canister purge, etc. That would be the first thing to check. Are you getting the check engine light any? Next just be sure all the ignition wires are routed properly. Front cylinders from L to R are "2, 4, 6" Back 3 are "1, 3, 5" Quote Link to comment Share on other sites More sharing options...
MadPSI Posted February 26, 2005 Author Report Share Posted February 26, 2005 Check to be sure you didn't break, crack, loosen a vacuum line at the back of the engine, going to the HVAC system, MAP sensor, canister purge, etc. That would be the first thing to check. Are you getting the check engine light any? Next just be sure all the ignition wires are routed properly. Front cylinders from L to R are "2, 4, 6" Back 3 are "1, 3, 5" I get a check engine light frequently. Usually comes on when the car's running alright. I'll pull those codes today and tell you what I find. The wires are routed correctly. It's kinda hard to screw that up doing them one at a time... Come to think of it, I did screw around by that MAP sensor quite a bit, I'll check those lines... Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted February 26, 2005 Report Share Posted February 26, 2005 Sounds like broken MAP sensor vacuum line to me. Quote Link to comment Share on other sites More sharing options...
MadPSI Posted February 27, 2005 Author Report Share Posted February 27, 2005 Sounds like broken MAP sensor vacuum line to me. You hit the nail right on the head... Codes 33 & 34 popped up (bad MAP readings) Also codes 44 & 45 (02 Rich & Lean, hmmm, wonder what caused that?) Popped the hood and, sure enough, the hard vacuum line was broken. Patched it up and all issues disappeared... What was throwing me for a loop was the car sounding like it had a miss just after startup, thought it was ignition for sure. Never knew the MAP would cause that. Oh well, back to emissions. Thanks... Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted February 27, 2005 Report Share Posted February 27, 2005 Ha, I win again! I did the same thing about two years ago changing plugs on my old 92, same symptoms you described. If the ECM doesnt get a correct MAP reading, it has no idea how much fuel to deliver. Quote Link to comment Share on other sites More sharing options...
Brian P Posted February 27, 2005 Report Share Posted February 27, 2005 Ha, I win again! I did the same thing about two years ago changing plugs on my old 92, same symptoms you described. If the ECM doesnt get a correct MAP reading, it has no idea how much fuel to deliver. hey slut, I mentioned it within my paragraph! LOL I broke that line on my old '90 cs as well, but a whole section kinda disintegrated. I used a clear piece of tubing that was pretty flexible, so when vacuum was high it would "pinch" and I was still getting issues. What a PITA that was! Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted February 27, 2005 Report Share Posted February 27, 2005 Ha, I win again! I did the same thing about two years ago changing plugs on my old 92, same symptoms you described. If the ECM doesnt get a correct MAP reading, it has no idea how much fuel to deliver. hey slut, I mentioned it within my paragraph! LOL I broke that line on my old '90 cs as well, but a whole section kinda disintegrated. I used a clear piece of tubing that was pretty flexible, so when vacuum was high it would "pinch" and I was still getting issues. What a PITA that was! I dont need a whole paragraph, I just get right to the problem! that sucks about that piece of flexible tube, never woulda thought that. On a side note, STE now has the 92's CD player Quote Link to comment Share on other sites More sharing options...
Brian P Posted February 27, 2005 Report Share Posted February 27, 2005 I dont need a whole paragraph, I just get right to the problem! that sucks about that piece of flexible tube, never woulda thought that. On a side note, STE now has the 92's CD player Quote Link to comment Share on other sites More sharing options...
MadPSI Posted February 27, 2005 Author Report Share Posted February 27, 2005 Ha, I win again! I did the same thing about two years ago changing plugs on my old 92, same symptoms you described. If the ECM doesnt get a correct MAP reading, it has no idea how much fuel to deliver. I'm guessing that the ECM compares MAP to TPS to throw that code, considering that the disconnected MAP assumes that the car's always at WOT... This was especially hard to diagnose due to the fact that I routinely beat the snot out of the car... Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted February 27, 2005 Report Share Posted February 27, 2005 Im not sure if it "compares" the two readings, but it sure would make sense if it did. Actually, an engine at WOT wont produced a negative pressure equal to atmospheric pressure. It will usually produce one a little below atmospheric. From what I have seen, when the MAP vacuum line isnt disconnected, it'll run real rough for 30 seconds or so, then idle normally, but wont have any power. I call this like "safe mode". Its like it has a set of default values of MAP readings that will allow you to limp the car somewhere if needed. Quote Link to comment Share on other sites More sharing options...
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