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| hard start, idle fluctuation (Page 1/1) |
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katie80
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JAN 29, 06:22 PM
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I have an 84 SE and since I bought it, the idle would never stay smooth. when I'm at a stop it sometimes will stumble and drop to around 500 rpm on the gauge and then climb up to around 2000 rpm and just keep going back and forth. sometimes it stabilizes after this but not usually. this happens more often when the headlights are on. it also starts hard when it's hot and hasn't been sitting long (if I give it like 10 minutes it starts like nothing.) im asking about them together because it seems like something could be causing both issues. any ideas what would cause it? the idle screw thing was adjusted by the previous owner and I have I set to a little under 1000 on the gauge, any less and it will not idle normally at all, any more and my idle is too high. here's a link to a video I took of me starting it, it shows the idle fluctuation as well.
https://youtu.be/VaEp7TFpwes
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katie80
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JAN 29, 10:03 PM
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I have discovered it only stumbles like that when the brake/turn signal is on. would replacing the bulbs with LED bulbs help with this issue? since the rear lights are run through a relay I imagine i wouldn't even need to replace the flasher. is that correct?
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Patrick
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JAN 29, 11:04 PM
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| quote | Originally posted by katie80:
I have discovered it only stumbles like that when the brake/turn signal is on...
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I'd perhaps check/clean up the ground for that wiring, located on the upper frame rail in the passenger side rear wheel well.
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theogre
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JAN 29, 11:53 PM
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Is called Hunting Idle and often cause by power ground(s) or both w/ problems. More so as turn on Headlights and/or brake lights affect crap idle.
"fan belt" maybe iffy too.
Worse, is 84 so don't use most electric diagrams for 85 - 88.
Check/clean all grounds in the engine bay and coat end bolted/screwed to whatever w/ silicone or brake grease.
Check/replace battery cables w/ ACdelco cable.
Check wires to starter solenoid. 2 are main power to rest of car.
Have alternator bench tested at local part store.
Also See my Cave, Alternator Sense
If C500 has damage where alt wires are... get worse and soon and could start a fire.
------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave[This message has been edited by theogre (edited 01-30-2022).]
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theogre
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JAN 30, 12:11 AM
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| quote | Originally posted by katie80:
I have discovered it only stumbles like that when the brake/turn signal is on. would replacing the bulbs with LED bulbs help with this issue? since the rear lights are run through a relay I imagine i wouldn't even need to replace the flasher. is that correct? |
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Don't do this.
LEDs as "drop in replacements" for external use on vehicles are Illegal in most US states and other countries and have many problems of their own and doesn't solve your problem.
some highlights, See my Cave, LED poisoning[This message has been edited by theogre (edited 01-30-2022).]
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katie80
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JAN 30, 06:15 PM
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| quote | Originally posted by Patrick:
I'd perhaps check/clean up the ground for that wiring, located on the upper frame rail in the passenger side rear wheel well.
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not a bad idea. the car is very rusty around the wheel well area so I wouldn't be shocked if I had a bad ground.
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katie80
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JAN 30, 06:20 PM
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| quote | Originally posted by theogre:
Is called Hunting Idle and often cause by power ground(s) or both w/ problems. More so as turn on Headlights and/or brake lights affect crap idle.
"fan belt" maybe iffy too.
Worse, is 84 so don't use most electric diagrams for 85 - 88.
Check/clean all grounds in the engine bay and coat end bolted/screwed to whatever w/ silicone or brake grease.
Check/replace battery cables w/ ACdelco cable.
Check wires to starter solenoid. 2 are main power to rest of car.
Have alternator bench tested at local part store.
Also See my Cave, Alternator Sense
If C500 has damage where alt wires are... get worse and soon and could start a fire.
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I think since it's whenever the rear lights are on the bright setting (for turn and brake) it could be a bad ground for that circuit. I will see about the other stuff come spring, it's too damn cold. i already had an issue with the wires to the solenoid, the rubber had fallen off at some point and it shorted out and melted, I replaced that part of the wire and installed a fuse since for some reason there is no fusible link there anymore.
with the alternator, I know the other gauges are not very accurate so I wouldn't be surprised if the volt gauge was too, it reads a constant 15v (the actual is closer to 14v. I have noticed recently in the cold, the voltage is closer to 18v on the gauge, but only when it's really really cold so I'm not sure why that would be.
this car has a lot of electrical gremlins already due to the previous owner having no idea what he was doing and trying to fix things.
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katie80
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JAN 30, 06:23 PM
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| quote | Originally posted by theogre:
[QUOTE]Originally posted by katie80:
I have discovered it only stumbles like that when the brake/turn signal is on. would replacing the bulbs with LED bulbs help with this issue? since the rear lights are run through a relay I imagine i wouldn't even need to replace the flasher. is that correct? |
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Don't do this.
LEDs as "drop in replacements" for external use on vehicles are Illegal in most US states and other countries and have many problems of their own and doesn't solve your problem.
some highlights, See my Cave, LED poisoning
[/QUOTE]
I was thinking to use low amperage LED bulbs that don't get very hot, but I'm not going to do that anymore. I have had good luck with the only LED bulbs in my fiero, the previous owner had installed them as footwell and map lights so I swapped them for those behind the gauges. I hate the piercing white color of LED so this is fine for me. I busted one of the tail light bulbs trying to see if it would still blink without any resistance from one bulb, but instead I broke the light. replaced with an incandescent bulb.
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theogre
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JAN 30, 11:46 PM
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"Perfect" volts w/ engine running is 14.7
Dash gauges or real meters can read a bit lower or higher.
Alt's regulator can be set a bit lower or higher too but over 15 you pushing many electric parts to die.
Read the cave link.
Iffy sense wire or output wire will cause high volts.
Jump alt output to A, large red wire, in side plug.
Jumper bypass 84 sense circuit w/o cutting/mod'ing.
if still has indeterminate high volts then likely iffy side plug or iffy alt.
Even then still likely has iffy ground etc causing hunting idle.
See my Cave, Wire Service
Adding fuse to alt output?
Exact fuse?
Alt out can push 50 to 105 amps depending exact unit used just staying with OE GM alts.
Wrong fuse or poorly install it won't help you.[This message has been edited by theogre (edited 01-30-2022).]
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katie80
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FEB 02, 03:02 PM
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| quote | Originally posted by theogre:
"Perfect" volts w/ engine running is 14.7
Dash gauges or real meters can read a bit lower or higher.
Alt's regulator can be set a bit lower or higher too but over 15 you pushing many electric parts to die.
Read the cave link.
Iffy sense wire or output wire will cause high volts.
Jump alt output to A, large red wire, in side plug.
Jumper bypass 84 sense circuit w/o cutting/mod'ing.
if still has indeterminate high volts then likely iffy side plug or iffy alt.
Even then still likely has iffy ground etc causing hunting idle.
See my Cave, Wire Service
Adding fuse to alt output?
Exact fuse?
Alt out can push 50 to 105 amps depending exact unit used just staying with OE GM alts.
Wrong fuse or poorly install it won't help you.
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normally the voltage is just under 15 on the gauge, so likely around 14.7v I don't remember where I read it but somewhere I saw that it's sometimes higher than that on startup. maybe I do have a faulty voltage regulator though, my ignition coil failed the other night after only 6 months of being installed on the car. the fuse is a 30 amp I believe, so far its been fine (that's all I had on hand). it's the wire to all the electronics (ecm, radio) when the wire melted the only thing that still worked was the lights so those are a different circuit as far as I can tell. should I swap for a bigger fuse?
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