Thread: lean at idle

just got done with a rebuild of my 02 gp gtp. N* TB, xp cam, zzp tune, 3.4 pulley, pacesetters, 180* tstat. i installed my wideband O2 sensor and its showing a lean condition at idle. no codes. as soon as i bring it off idle it goes stoich. the car has been sitting for 9 months with 3/4 tank of gas. this issue is confusing the h*ll out of me. im wondering if its old gas... vacuum leak... im not sure. any help would be appreciated. i lost the first engine due to a lean conition cuz im a retard and slapped the pulley on it with no tune.

does that tb have the maf installed on it? if so, make sure it has the screen in it. i removed my screen and ran lean at idle.

lean at idle is normal....

its also lean when crusing, as long as its not lean when WOT things are okay.

What was your wideband showing? Mine sits at 14.7 or 14.8 when its warmed up at idle.

XP Cam.

Originally Posted by FoSHO99

XP Cam.

Is the issue...its not big enough That and ZZP tuned the PCM.

a lean idle is normal

the wideband is reading 17-18:1 at idle. and yes the screen is in the maf and the maf is in. besides the zzp pcm is temporary until i can get it dyno tuned. but its a long drive to the dyno.

lean idle doesnt matter so long as its not a symptom of another issue.

hmm well im gonna go look for other issues later tonight. homework comes first :-(. any suggestions on where i should start looking? vacuum leaks? iac? mini tazmanian devils stuck in the throttle body :-) any suggestions will be helpful.

my first thought is a vacuum leak.

ok thanks bio ill prolly start there

The boost gauge was dis-connected (very small vac. leak) reconnected= no difference. When I touch the throttle its goes stoich. then fastly creaps back down to lean (17.1-18.1) at some points my AEM UEGO wide band will not even read the extreme lean mixture. All this is happening with the engine cold. With it running this lean i do not want to keep it running so it does not get up to operating temp.

I have tried:
*putting the stock TB unit with all good sensors = same thing
*disconnecting vac. line from fuel pressure regulator (both TH units) = same thing
*northstart throttle body with and without TAC chip in harness = same thing
*Both stock and ZZP ecu's = same thing

is it missing at idle??? i know a guys truck that did this and one of the push rods was not seated right and the valve hung open. but it also had a mis at idle.

no misses, when you start the engine its runs at about 13:1 and it slowly leans out and you can hear and watch the engine run different as the AF ratio leans out.....

i just cant figure out if the engine is supposed to lean out when it idles, maybe a little but not over 18:1 thats a little extreme.....

18 does seem a little high

yes, very! at some points it wont even read on the wide band..............
!!!!ANY OTHER THOUGHTS OUT THERE!!!!

Try to get a scan up, mainly where the fuel trims are.

With an xp cam, you are going to have misses at idle, that is partly why the lope is, this is also why they disable the engine misfire trouble code when installing higher lift cams.

What type of wideband is it? Some of them need to be calibrated in open air before install. It's normal for the wideband to take about a minute or so to warm up and read the correct reading. Usually you will see it go from 14 to air in a minute or so if you hook it up and leave the sensor in open air.

it is a AEM UEGO wide band kit........