PTAaron Posted May 21, 2014 Report Share Posted May 21, 2014 (edited) EDIT to update: The "thumping" in the speakers seems to be present mostly when the blower (vents) is on. The lack of power comes on when the thumping is present. It seems to happen when the car has been driven, then parked for 10-15 minutes and driven again. If it sits for longer than about 30 minutes the problem does not occur. Also noticed today that the "battery" gauge is reading extremely low - when the AC is on it drops almost to the 8v mark, when the engine is at idle and the blower is off it bumps up slightly to maybe "9"? I"m including pictures later in the thread. Original post: Okay - this was a strange one last night. Drove the '94 Cutlass Supreme to work, stopped off at the store near home to get some things, got back in the car to go home and on the first attempt at starting the car stalled out immediately. Second attempt it started really rough and there was a loud "thud thud thud" noise coming through the speakers even though the volume was nearly off. I revved it a few times and the idle smoothed out - drove the 3/4 mile back to the house and when I pulled into the driveway I could only make it halfway up the driveway! The engine revved, but the car didn't move! Some friends were coming over - so I let the car sit for about 2 hours, then started it up - no issues - and pulled it the rest of the way up the driveway into the garage with no problems. Drove the car to the gym this morning - no issues. Any idea WHAT would make the car do that?? Within the last 1,000 miles the car has had: new headgasket, new water pump, new MAP sensor, new ACT, new fuel filter, new fuel pump, new plug wires, plugs checked and regapped, several oil changes (because of the headgasket replacement), new starter, and some brake lines replaced after blowing out. I checked the trans fluid level - it looked good, but brown and probably in need of replacement; oil level was good and still clean looking... I know nothing about automatic transmissions - except from the perspective of removing them to install a manual, so they are a magical mysterious thing to me... but it seems like something between the engine and the wheels would be the culprit? but why would it suddenly work fine? Thanks for any ideas guys. Edited June 2, 2014 by PTAaron Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted May 21, 2014 Report Share Posted May 21, 2014 did the thumping through the speakers happen to change with engine speed? or were you not listening for it? Quote Link to comment Share on other sites More sharing options...
PTAaron Posted May 23, 2014 Author Report Share Posted May 23, 2014 It happened right after startup and I turned the radio off because I was trying to listen to the engine... so its hard to say. Before the headgasket replacement and all of the things that went along with that I would sometimes hear that "thud" when sitting in the garage with the key on/engine off trying to listen to the end of a song on the radio though. Quote Link to comment Share on other sites More sharing options...
PTAaron Posted June 2, 2014 Author Report Share Posted June 2, 2014 Today the "thumping" was there off and on most of the drive into work - I figured out it is there when the blower is on, worse when the AC is on, goes away when blower is turned off. Lack of power is there when the blower is on and thumping is present. Also noticed that the battery gauge is reading EXTREMELY low. This is at idle with the blower off: This is with the blower on "bi level": Also when the turn signal is on the needle bumps down each time it blinks... so... alternator? Seems like the most logical thing... but I don't see how that would relate to a loss of power? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 2, 2014 Report Share Posted June 2, 2014 confirm system voltage with an actual multimeter, underhood, preferably using the intake manifold as a ground and the aux positive terminal as positive. those readings are really alarming. if they're anywhere near reality, then you have at a minimum a serious charging problem; charge wire, battery, alt, fusible link, engine/trans to frame ground, something. really low voltage will cause all kinds of problems, including lack of power if the fuel pump can't keep up with the engine's airflow. Quote Link to comment Share on other sites More sharing options...
PTAaron Posted June 2, 2014 Author Report Share Posted June 2, 2014 confirm system voltage with an actual multimeter, underhood, preferably using the intake manifold as a ground and the aux positive terminal as positive. those readings are really alarming. if they're anywhere near reality, then you have at a minimum a serious charging problem; charge wire, battery, alt, fusible link, engine/trans to frame ground, something. really low voltage will cause all kinds of problems, including lack of power if the fuel pump can't keep up with the engine's airflow. It has always read low - but never THAT low. Usually between the line below 13 and the 13... but the level it was at this morning is a new thing. Will confirm actual voltage when I get home tonight with multimeter. Quote Link to comment Share on other sites More sharing options...
PTAaron Posted June 4, 2014 Author Report Share Posted June 4, 2014 Last night I got out the multimeter and tested from the alternator to the intake and got around 13.9v while the gauge on the dash was reading at the first big line above 8. That was with the engine running, headlights on, but blower off (I forgot to turn it on). Reading from the intake to the positive post sticking up near the battery gave me just over 12v. I tested again through the cigarette lighter socket in the car with the AC on, headlights on, engine running with the needle reading just barely above the 8 - restarted car after it sat for a while - and I was reading 13.0 there. Not sure what to think... When the needle reads low I can see the headlights brighten and dim at night... The turn signal makes the other dash lights dim, and that loss of power issue crops up when the blower is on. Only thing that was changed before this started (I just realized this) is that we replaced the starter with a good junk yard starter. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 4, 2014 Report Share Posted June 4, 2014 i think you have some significant resistance on the charging wire..... either a bad connection(since you mentioned the new starter, i would look there since the stock charging wire relies upon the starter post) or a wire that's about to go from high resistance to infinite resistance. Quote Link to comment Share on other sites More sharing options...
PTAaron Posted June 5, 2014 Author Report Share Posted June 5, 2014 I will check out the connections there and figure out what the charging wire is and report back! Thanks for pointing me in a direction! once I remembered that we just did the starter a few days before it started acting I figured that would be a logical place to start but I didn't know how it fit in with the charging system. Quote Link to comment Share on other sites More sharing options...
1990lumi Posted June 11, 2014 Report Share Posted June 11, 2014 to me it sounds like you have a ground loop someplace in the car Quote Link to comment Share on other sites More sharing options...
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