HELP-low idle misfire
HELP-low idle misfire Hey all,
I have a low idle issue with my 97 Trans Am and its starting to aggravate me.
After about 15 minutes and the car warms up, it starts to misfire and hesitate at idle...if you give it some gas, it goes away and runs smooth. When its cold, it runs smooth.
I changed out the coolant temp. sensor mounted on the pump but that didnt help.
I need to change the plugs and wires in it (125K miles on them!), but if it were ignition, woudnt the hesitation be all the time and not just when it gets warm?
Could it be O2 sensors, they are original on the car as well.
Optispark was replaced about 17K miles ago as well as cap and rotor.
I am lost....................
I have a low idle issue with my 97 Trans Am and its starting to aggravate me.
After about 15 minutes and the car warms up, it starts to misfire and hesitate at idle...if you give it some gas, it goes away and runs smooth. When its cold, it runs smooth.I changed out the coolant temp. sensor mounted on the pump but that didnt help.
I need to change the plugs and wires in it (125K miles on them!), but if it were ignition, woudnt the hesitation be all the time and not just when it gets warm?
Could it be O2 sensors, they are original on the car as well.
Optispark was replaced about 17K miles ago as well as cap and rotor.
I am lost....................
definitely sounds like O2 sensors, and if you're not sure just have autozone scan it for free--I'm sure you'll see the codes. The whole "warming up" thing indicates problems once she's in open loop.
Thanks, I will head there on the way home and have them scan it. I think the LS1 cars have 4 if I am not mistaken......are there two or four on the LT cars...sorry, I just bought it and I am up in my office at work right now. Thanks again!
I looked it up and found that there is only one part number at the local autozone but have researched and that GM has two part numbers.......what the difference? I assume it has to do with the temperature of the exhaust???
Thanks for the help.
Thanks for the help.
On The Tree
Joined: Feb 2005
Posts: 116
Likes: 0
hey if you figure this out let me know!! ive been having the same problems out of my 95 ta. ive done plugs,o2s and changed out the PCV valve and its still there. no ses light at all..
when its cool outside the car runs fine. warm weather the car starts up and idles funky and then goes away after about a minute
when its cool outside the car runs fine. warm weather the car starts up and idles funky and then goes away after about a minute
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I will post up my findings.....advanced auto guy tried to put the OBD II scanner on it and said my ecm was bad..his scanner couldnt pick up the computer....I am like huuhhh? local shop said they didnt know their a$$ from a hole in the wall.
I just met another wrenchhead that lives about 5 minutes from me and he has one...we are going to diagnose it...if its not the O2 the next step would be to check the EGR out. We shall see.
mike
I just met another wrenchhead that lives about 5 minutes from me and he has one...we are going to diagnose it...if its not the O2 the next step would be to check the EGR out. We shall see.
mike
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Staging Lane
iTrader: (6)
Joined: Dec 2006
Posts: 87
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From: lockhart texas (30 min from austin)
I've got the same prob with my car. So far I have replace the opti, cap and rotor, plug wires, plugs, injectors (used but with less miles), cleaned the iac, cleaned the map sensor, cleaned throttle body, and tried some other little tricks. I ran the car last night after the injector swap and coul not get it to start missing out like it usually did, but I will try a longer cruise today cause I am sure I am still going the wrong direction with it, but don't have a scanner for obd 1 (95 model t/a). My car does the same exact thing although. After some warm up time, it starts to miss at idle, sometimes like it wants to die and then it kind of chugs once I hit the gas until the rpms spin up just a bit to cruise speed.
Staging Lane
iTrader: (6)
Joined: Dec 2006
Posts: 87
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From: lockhart texas (30 min from austin)
Injectors didn't help at all. My egr was deleted from the computer during the tuning process so I pulled the egr and built a block off plate. Figured the egr may be hanging open even though the syptoms I am accustomed to of a malfunctioning egr aren't what I am having. Yep, it didn't help. I am thinking o2 sensors for sure now. Gonna pull em to inspect and clean. For all I know, one of them could be melted. I've seen it before.
Staging Lane
iTrader: (6)
Joined: Dec 2006
Posts: 87
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From: lockhart texas (30 min from austin)
I have roller rockers with poly locks. I readjusted them and even replaced two puch rods until I found out that the clicking was a header bolt that fell out. Still not the cause of my miss. Plus I would think that a misadjusted valve would cause a miss at higher rpms also rather than just at idle and low rpm takeoff.
Staging Lane
iTrader: (6)
Joined: Dec 2006
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From: lockhart texas (30 min from austin)
Pulled the o2s tonight. Soaked em in solvent and cleaned with carb cleaner. Will see if it helps. Broke from all the damn parts I've replaced so far so new o2s will have to wait.
Staging Lane
Joined: Dec 2005
Posts: 59
Likes: 0
From: San Antonio, TX
As of yesterday I noticed the same issue. I haven't driven the car in 3 days and it's been raining like crazy and really humid so I went to start it up and once the rpms dropped and it heated up I got what feels like a miss to me. It comes in surges and the but the tach are not jumping around when it happens. Car never dies and when I gave it a drive around the block it ran smooth giving it gas.
I was begining to fear mositure got into the opti or somthing but I just replaced it a few months ago and I would think it would mess up not just at idle. There is no hesitation at start up either.
My car isn't tuned yet either since my rebuild so i'm sure that isn't helping.
I was begining to fear mositure got into the opti or somthing but I just replaced it a few months ago and I would think it would mess up not just at idle. There is no hesitation at start up either.
My car isn't tuned yet either since my rebuild so i'm sure that isn't helping.
