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starting problems 2003 STS

2K views 19 replies 3 participants last post by  sts 03 
#1 ·
I've been having starting problems lately, sometimes it will click when turning the key other times it will start to turn over then stop .it will also crank but act like or will cut off.yesterday when it cranked it started idling under 500 rpm and was about to stall and the messages started coming across the dic I can't remember word for word but one said service charging system and the other I think said battery not charging and the warning light came on.it finally started idling around 500 rpm and if I kept my foot in the throttle the warning messages and light went away.the only two codes I have are p0621 history- generator lamp L control circuit malfunction, the other p0506 current- iac system rpm lower than expected.if iac sensor is faulty causing a low idle could that cause the p0621 or vice versa?
 
#3 ·
Yeah I cleaned both of those last year, but I checked them today just to make sure and both are still clean .today when I started the car it kept cutting off as soon as I cranked it, if I kept my foot on the gas it would stay on then after it warmed up some it would stay on by itself idling at 500rpm.could this be the iac?
 
#4 ·
Yes. If it won't stay running unless you have your foot on the pedal, keeping the throttle plate open, the engine intake is being choked off. By holding the throttle open you are doing what the IAC valve is supposed to do, and that is provide just enough intake air to keep the engine running.
 
#6 · (Edited)
Yep it was clean in there when u checked yesterday,a dirty tb wouldn't cause the car to just click sometimes when I try to start it sometimes would it? Sometimes it clicks before it finally starts then sometimes it stalls or wants to stall after starting.but like yesterday I had to hold my foot on the gas to keep it running till it warmed up then it idled at 500 rpm.I've been having random high/low idle for the past year.is there anyway to test the iac without using a scan tool?
 
#11 · (Edited)
Forgot to mention I had a random miss fire code twice recently, both times when the car was acting like it was going to cut off.so today only current code is p0506 iac rpm lower than expected.same thing today also when I crank it it starts then stalls right out unless I hold steady throttle for a few then it will idle at 500 rpm and if I rev it it will stall .also there was a strong gas/exhaust smell when I first started it.I found a new Delphi iac for only $57 does this sound more like a bad iac?
 
#12 ·
Well the Idling issue is definitely the iac ,I took the iac out and the car didn't stall even though the idle was Choppy due the the vacuum leak, then the iac plunger shot completely out across the engine.I screwed it back in and when I start the car the Idle is high so maybe I screw the plunger in to far.could a failing iac cause a random miss fire code due to the low idle/stalling ?
 
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