gmrulz4u Posted June 16, 2004 Report Share Posted June 16, 2004 Today I confirmed another clue as to what is wrong with my 89 Supreme. For some reason, VERY small voltage drops are causing the engine to hesitate and "stumble" while idling. For example, the engine is up to operating temperature...I pull into a drive-way and put the car in Park...while I'm sitting there idling, I turn ON the four-way flashers...each time the lights flash ON, the engine hesitates and stumbles a LITTLE, and the vacuum drops 2" hg...each time the lights flash OFF, everything smoothens-out and the vacuum goes back up...now imagine this happening back and forth every 2 seconds as the lights are flashing ON and OFF... It's not JUST the four-ways...it's any electrical load...even opening the door(turning interior lights ON) causes the same thing... And NO it's NOT the battery or alternator. I have verified multiple times that both are working perfectly. Both are not even 1 year old and I'm getting a steady 14.5 volts while running... If I sit and watch the voltage as the four-ways are flashing and the engine is "stumbling" slightly...I can see with my digital multi-meter that the voltage is hardly dropping at ALL...it might go from like 14.5 to 14.1 but nothing major... So why the heck is the engine being so affected by this!!?? Is it the ECM?? So far I've discovered the following about the ECM: 1) Engine is "stumbling" slightly when voltage dips a half volt or less 2) ECM is setting codes even though criteria for code is NOT being met 3) ECM is losing control of IAC or "forgetting" IAC positioning I'm guessing it's time to get a NEW ECM?? Anyone ever experience this type of thing?? THANKS! Quote Link to comment Share on other sites More sharing options...
THe_DeTAiL3R Posted June 16, 2004 Report Share Posted June 16, 2004 have you tried cleaning or replacing the IAC? When mine was reallly dirty it made my car run really weird and would stall all the time. I didn't pay attention to the voltage, cause of the stalling. Anyways, good luck Quote Link to comment Share on other sites More sharing options...
GP1138 Posted June 16, 2004 Report Share Posted June 16, 2004 I notice the exact same thing. If you turn on the interior light you can see it better. Turn on your turn signals or hit the brakes and watch your volts drop and your lights dim the slightest bit. Why the hell a turn signal takes so much voltage to work, I don't know. Quote Link to comment Share on other sites More sharing options...
THe_DeTAiL3R Posted June 16, 2004 Report Share Posted June 16, 2004 Heh... when I drive at night (headlights on) and turn my stereo to "safe maximum" (according to me).. Kenwood 460w RMS bridged to a 12" Pioneer sub, and a 40w x 2 amp for the doors.. the voltage guage bounces up and down a little, especially with hip-hop But yeah, for some reason signal lights seem to take up the most.. who knows. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted June 16, 2004 Report Share Posted June 16, 2004 I notice the exact same thing. If you turn on the interior light you can see it better. Turn on your turn signals or hit the brakes and watch your volts drop and your lights dim the slightest bit. Why the hell a turn signal takes so much voltage to work, I don't know. Well, the whole car runs on 12V so its not the volts that are being used, its the current (amps). I think the turn signal bulbs on the rear of the car are between 30 and 40 Watts each. There are 3 (on my STE for example) on each side of the rear part of the car, all drawing around 3amps of current. So 6 times 3amps is 18amps just for the rear. The front signals dont require near as much, but total, Im going to guess about 20-25 amps is needed to run the signals.....this is about 1/4 of what the alternator puts out. It also has to run other things on the car, so 20-25amps extra is a pretty good load. I know I made of a lot of simplifying assumptions, but it should still be pretty accurate. (To get the 3amp number for the rears, I took the power 30-40 Watts and divided by the voltage 12. Since P=V*I, I can do that:) ) Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted June 16, 2004 Author Report Share Posted June 16, 2004 Yeah but I don't understand why the engine itself is affected so much...I understand that maybe the voltage will drop and the lights will dim...but why in the hell does that make the engine hesitate and stumble!? That's what makes no sense... Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted June 16, 2004 Report Share Posted June 16, 2004 try a new ECM. Its like the only thing you havent replaced on that motor, right? Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted June 16, 2004 Author Report Share Posted June 16, 2004 try a new ECM. Its like the only thing you havent replaced on that motor, right? Yeah...pretty much...there's a few sensors I have changed like the ECT or TPS...but I've already verified they're fine... I'm going to check the injector resistance next... Quote Link to comment Share on other sites More sharing options...
Canada Posted June 16, 2004 Report Share Posted June 16, 2004 What codes are being set? Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted June 16, 2004 Author Report Share Posted June 16, 2004 The code that gets set most often is 45...indicating a Rich exhaust...but I'm only running Rich at idle because I have a A/F gauge installed... Quote Link to comment Share on other sites More sharing options...
loominaz34 Posted September 19, 2004 Report Share Posted September 19, 2004 Hey guys, my car's doing the same thing except it dies completely when I turn the lights on, the voltage goes from 14.2 at startup to 13.7 about 2 minutes after but the battery itself is not charging. In addition, it's running really rich. help. please? Quote Link to comment Share on other sites More sharing options...
loominaz34 Posted September 19, 2004 Report Share Posted September 19, 2004 Also, how do I clean the IAC Quote Link to comment Share on other sites More sharing options...
Regal_GS_1989 Posted September 21, 2004 Report Share Posted September 21, 2004 It sound like you could have a weak alternator. If it seems to charge fine, put a load on it and then check. If it the voltage is less than 14 volts, the rectifier is probably gone. Quote Link to comment Share on other sites More sharing options...
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