running lean...

[Camaro Dom]

i've posted this ongoing problem a few times already without getting any real answer. Ok, for i dont know how long, i've had codes for all three o2's running lean. I looked at the fuel trim with one of those rent-a-scanners and it said i was running like 15% lean (i forget the units so % may not be right). anyways, so its not the o2's. i did a seafoam; plugs, wires, pcv, and fuel filter all got changed last x-mas time (so like 5k miles ago). it doesnt seem to lack power except when i start it from dead cold and drive immediately. if i let it sit for a minute and idle it's fine. if i dont, i barely get any throttle response and it takes forever for it to shift to second. i did a vacuum test and the needle was at about 20 mm but vibrating pretty eratically +/- 1mm. its got a pretty rough idle, ESPECIALLY when i do that start from dead cold. it sounds like it has a monster cam for about 30 seconds before it settles down. PLEASE help me get this figured out! its driving me crazy that its taken so long to begin to figure it out!

[slow6]

Re: running lean...

intake leaks, bad o2s, ported maf?
if it lacks power at startup, it would be in Open loop until the coolant got to 68*F.
Open Loop doesnt rely on o2s, its purely MAF

[97rs4life]

Re: running lean...

have you replaced your 02 sensors yet? If they are bad then the pcm is getting bad reading from the sensors and not adjusting the fuel correctly.

[Camaro Dom]

Re: running lean...

i replaced the post cat one but that didnt do jack. the thing is, when i had the scanner, it gave me the voltage readout from the o2's. they were bouncing b/w rich and lean at idle. i know that thats called "toggling" and they're supposed to do that. If i clear the codes, they dont set until i'm on the highway passing someone (i.e. hard prolonged acceleration). I dont know how else to test teh maf sensor. I ran some electrical cleaner on it. i smacked it with a screwdriver (haynes says if the engine stutters when you hit it you know its bad). its not blowing codes for the maf and i dont feel like shelling out 200 bucks just to find out it wasnt the maf after all...

[slow6]

Re: running lean...

the pre-cat and post-cat o2 sensors dont have anything to do with your AFR (Air to Fuel Ratio %) (fueling). All they do is tell the PCM (car's computer) that the cat is working or is not working (clogged or not).

What were the readings of that scanner? Narrowband o2 sensors cannot be trusted cause they arent that accurate(they have a limited margin of being accurate 0-5v).
How long has it been since you changed o2 sensors? They are only supposed to last 60k miles

[Camaro Dom]

Re: running lean...

the stock ones are as old as the car (100K+). when i saw them they were bouncing back and forth b/w like .200 and .800v. i dont remember the number exactly but i know that it said rich-lean-rich-lean-rich-lean. before i shell out 150 bucks for new o2 sensors i wanna be SURE i'm not overlooking something stupid. i got the car at 60k and it was sending the same codes. i've only been getting concerned with it now cuz of the rough idle and weird start up routine. that and the engine seems to "come alive" at 4000 rpms. it seems to have mediocre pick up but once it hits 4k, i feel it really pull me into my seat. that my be my ram air but i doubt it...

[slow6]

Re: running lean...

dude, please get new o2 sensors
it will save gas
when the o2 sensors switch lean/rich/lean/rich thats normal
they are just narrowbands
if it was a 2002 and you brought it to my city, ya dam right i would tune it for free (kind of like an internship) so i could get extra experience

[97rs4life]

Re: running lean...

yea the exhaust manifold o2s are what control air/fuel ratio

[Camaro Dom]

Re: running lean...

ok but then why is it acting so weird when its in open loop?? haha slow ya damn right i'd be over there with ya trying to learn how to tune... too bad we're only like 1500 miles away LOL

[Camaro Dom]

Re: running lean...

AH HA! heres something: just blew this code today: P1518. The code reader was crappy so it abbreiviated everythign but z28.com said: DTC P1518 Electronic Throttle Module to PCM Communication. now what the hell does that mean? bad ground? bad throttle motor? what?

[Camaro Dom]

Re: running lean...

ok... i've given up. to the dealer it goes. it sounds (and feels) like i busted the cat (again). I'll bet it'll be the result of all this running lean...i cant figure out what the problem is and I cant deal with this anymore.
If it turns out i did bust the cat, i'm gonna put a magnaflow muffler on in place of it. i'm sick of breaking cats (this one will be 3 in two years) and MI doesnt do inspections. where do i get an O2 sim at? are they plug-n-play or is there crap i gotta do b4 it'll work?
*sigh* this just sux. i'll give an update in a week or so when i get back from outta town.

[slow6]

Re: running lean...

no way a cat could make you go lean, its gotta be something else
i'm not sure if a shop will want to not put a cat on
yes its P'n'P

[Camaro Dom]

Re: running lean...

i know the cat wont make it run lean, i'm just thinking that whatever problem i have probably killed the cat. it might explain why i've already gone thru 2 of em and maybe a third.

[Camaro Dom]

Re: running lean...

:UPDATE:
ok... so i'm back from the dealership finally. ok ok. i'm too lazy to look who said O2's but i'll admit... you were right. they did all 3 O2's, an injector, an ignition coil and the wiring to my throttle. also said there was some corrosion on some wire or another that they cleared out. they also changed out my fuel level sensor. she purrs like a kitten now. its beautiful.
apparently #5 cylinder was in a world of hurtin'. Bad injector AND bad ign coil. poor lil guy... :p