2003 grand am gt high idle (major issue!)

[Talon69]

well i have searched this forum and all over the damn net and cannot find any info that will solve my issue

So here we go, about 2 years ago my grand am 3.4 would idle high once in a blue moon, 2,500rpm, then about a year later when i took it on trips longer than 30 minutes it would do it every time at 2,500 rpm, now present day it does it as soon as i start it up, idles at 2,500 to 3,000rpm, i cannot figure it out for the life of me. I have changed the TPS,IAC, cleaned the throttle body, checked for vacuum leaks the best i could, i use carb and choke cleaner. MAF sensor seems fine. I unplug the new TPS and no change, still idles high, so the tps is working. My cluster also goes wacky, but has done it for a long time, gauges will bounce around, sometimes they work, sometimes they dont, clucter warning lights will take turns going on and off, but the cluster issue i believe is a bad cluster as grand ams are known for that issue. Would a bad ecu cause my high idle and progressively got worse? I also tried to hook a scanner tool up today and all it kept saying was, link error, tried at least 15 times. Tried it on another car to make sure scanner was good, and worked perfect.

although when i unhook the MAF it will stumble and idle down for a split second then back up, then once i plug it back in, it will idle down for a split second then back up. When i say idle down, it will go from 3,000 down to about 2,000 then back up

Hopefully someone can shed some light on this

[Tech II]

Most techs have an idle air control tool......you disconnect the harness, attach the tool, and you can increase/decrease the opening of the passageway, via the pintle....

Or you look at the IAC counts on a scan tool while the engine is running....if idle is high, but counts are low(under 15), then you have a vac leak......if the counts are high, then the IAC is being commanded high by the PCM.....

One thing I have found, is an intermittent connection in the IAC harness....either the female connectors are spread/loose, or you could have a broken wire inside the insulation making an intermittent contact(usually breaks within 5" of the harness end).....

Sounds like you may have some wiring problems, with your cluster acting up too....

Another thing to try, get the car to normal operating temp...shut vehicle down....turn key to on, don't crank....disconnect the IAC harness...now start car and see what idle does....

[Talon69]

well here is my thread i have going at another place, not sure if this will help out at all.


Originally Posted by melsg5
have you checked for a blown cigarette lighter fuse which powers the OBDII port?
do you have a check engine light on?

(ME) cigarette lighter works fine, thats the first thing i checked. I left the battery unplugged all night, hooked it back up after work today and took it on a 40 mile drive down the highway, got off the highway coming to the red light and was still idling at 3,000rpm, proceeded to the next light same thing, 1 mile further down the road i pulled into autozone and it started idling normal at 700rpm's , i had them put the scanner on it just to see if it would link since my check engine light is not on at this time. There scanner tool would not connect either. I also pulled the ecu out last night and checked the connections, all was good. So i left autozone, brought the car home and still idling normal. No idea what is going on, but i do know damn well it is going to idle high again, i am willing to bet once i get home from work tomorrow and start it up, it will be idling high, maybe not but i do think so

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Originally Posted by richardgriese
Watch it be something dumb like the throttle cable. See if autozone checks for history codes as well.

On the cluster I suppose it's the stepper motors going out? Either buy some new stepper motors and put them in or go to a junkyard and get a new cluster. I think mileage is stored in the cluster on these GA though. I have seen a few people do a work around but on an old car... I would just want it to work.

FYI I picked up a cluster from a jy (for in impala) it was $35 so theses aren't too bad. I'd be curious to see some live data.

Do you do the work yourself? I saw you posted about getting the LIM done.
Not the throttle cable as when it is idling at 3,000rpm, the throttle body flapper is completely closed.

(ME) With the cluster, its not just the gauges that go crazy, all the warning lights in the cluster take turns going on and off as they please. Sometimes all will be normal, then next thing you know, some of the gauges are not working and some warning lights going on and off, then a gauge will start to work and like the fuel gauge wont work, speedo needle will go from like if your cruising at 40mph, it will bounce from 40 to 120 then back to normal.

I cannot see if any codes are stored at all, as I described I cannot get a scanner tool to connect to the car. Keeps saying link error.

yes, I do all the work myself always on my vehicles, I changed the LIM last summer myself, pretty easy to do.

One last thing, not sure if this is a coincidence or not, but when I left autozone and the car was idling perfect, the cluster did not act up at all, was completely normal. So I will see how it will go after work today. Im curious now if this idle problem acts up when the cluster screws up. IF that is the case, then maybe a major ground issue?

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Originally Posted by richardgriese
It seems like some type of an electric issue maybe computer but that's more on the extreme end. Yeah see if cluster issue = high idle.

Interesting you cannot get the car to read... Has anyone sliced into these wire or installed a aftermarket radio strangely? I've seen people do some crazy splicing and other weird electrical re-wiring. Then if cluster malfunctions and car goes crazy would it do it with the cluster attached?

(ME) I bought the car almost 5 years ago now, the first week I had it, I removed the stock stereo and installed a aftermarket one. All plug in play along with the chime box. I think it would be safe to say the stereo is not the issue since I did not have any issues the first 3 years with the car.

I agree, very strange I keep getting link error with multiple scanners that have been tried. ECU is not really to bad if I decided to try one for the hell of it, There is a shop on ebay that sells them and once you click buy it now, you give them your vin# and they will program it to your car for you. $75 shipped.

Well, got home from work and started it up,and of course idling at 3,000rpm, cluster screwy also, drove it again 40 miles and back home, still idling high, cluster still acting up, i let it just sit there and idle high for about 10 minutes, screw it. All of a sudden the idle went down to normal, but the cluster was still acting up. I let it sit there and idle for 16 minutes, then all of a sudden it creeped back up to 1,500rpm and thats where it stayed, i shut the car off, started it back up, now its idling at 3,000rpm , then after a minute it dropped to 2,000rpm. Shut it back off, let it sit for about 5 minutes, started it back up, now idling normal, but once again after a little bit it creeped back up to 1,500rpm shut it off, let sit for 30 seconds, started it back up and idling normal, just went back out after sitting 15 minutes and still idling normal, i know for sure it will be all screwy again after work. I do not understand what the hell is going on.