View Full Version : Bad MAF ?
01-09-2005, 07:19 PM
Ok after going through the money and time the car was idling slow and missing, throwing p0300, broke down and replaced brand new bosch platinums with new
ac delco pro platinums and it idles smooth babies behind. I did not believe plugs
could cause this.
Ok my kids 00 ga se1 3.4 through the SES on today, and the idle is a little surgy, and pulled codes for TOO RICH P0172, multiple missfires, and HSO2-1 bank one
oxygen sensor failing to switch.
So I replace the O2 sensor in manifold, and codes not clearing, pull battery as
my predator is for my v8's and won't reset the v6, codes clear and I watch Long trims heading rich fast, you know from 0.00 to -18.50 in a few minutes and according to my manual over -18% will throw a code. So it's too rich, I checked fuel rail, it's 42 psi at idle 48 off idle. Then pulled power from MAF and numbers
started to head lean, went to about a 3.00 long term , so is the maf gone?
Must be reporting a crap load more air than it really is getting. The idle showed
I think about .6 to .8 lbs.
01-11-2005, 09:50 AM
OK still looking for guidance, ther MAF helped (maybe), the LT after being reset quickly runs to about -10% now , which keeps any codes from setting but WHY is
it so far off ? My other cars/trucks run within 3% of Zero. I mean if it was correcting
for a LEAN I could start looking for leaks etc BUT RICH means lack of air or too much fuel, and I know the fuel pressure is OK. It appears to all across the fuel trims as I can see it go into different trims and start pulling fuel till the same -10%.
So I'm getting to much fuel from ?? Did plugs recently and no single fouled plugs noticed so it seems injectors are normal, replaced oxygen sensor first.
Idle still slightly surgy, vacuum running 17-17.5 and idle SEEMS low, 700-750.
Also checked intake system, no blockage.
Please GURU's jump in here.
01-12-2005, 08:06 AM
OK still looking here for help, last night we pulled the TB off completely, cleaned it up, replaced pvc, checked over entire intake system. Still not throwing the codes but saw it get close at a LT of -14% . FYI the car runs fine, idle could be smoother, but at 89K miles and such it's a tad low, 700 rpm, in or out of gear.
01-12-2005, 08:21 AM
I'm no guru, but unless your MAF is descreened (had the screen removed), that's probably not it. You mention that you have replaced the pre-cat o2 - did you use a bosch replacement sensor? I have heard that they are hit-and-miss; some people have no problem with them, others have nothing but problems with bosch sensors. If so, I would recommend using an ACDelco o2. Also, what plugs did you use? MANY people have problems soon after replacing stock plugs with Bosch platinum plugs. If so, I recommend NGK or ACDelco.
01-13-2005, 04:37 PM
OK got another maf from autozone, it made a big difference, the LT is now -3.4 to -4 , BUT my kid was going to school and through the ses, Now a p0300 MAF
to low, and his idle is 650 , why doesn't the pcm through a code for IAC not working? Or what else causes a low idle?
01-13-2005, 04:48 PM
its normal for it to idle that low...my car has idled at 550-650 ever since i got it...same as everybody else i know that has a GA 3.4
02-01-2005, 09:51 PM
plugs with multiple tips/ gaps can cause idling probs run probs i had that with ngk and bosch now i only use ac delco double platinums they are like $6-$8 a plug here
02-25-2005, 01:30 PM
Does anyone know if a bad o2 sensor would cause your car to idle like it has a misfire? I changed my spark plugs a couple of weeks ago and the car was running fine. A couple of days ago it seemed like my car was misfiring while idling and my SES light was on but it didn't show a cylinder misfire, instead, it showed a P0141 code for an O2 sensor. If I replace the O2 sensor, would the idle return to normal or should I get it checked by a mechanic? Also, someone told me I might have a bad valve but that's more stress I don't need. Any suggestions, please let me know.
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