stubborn SES light costing me a lot of $$$

[Stangboy017]

ok, so I have a 99 GT, put a Steeda cat-back on about a month ago, about a week ago had a Magnaflow cat'd X installed. After I got the car back the service engine light soon popped on. I went back to the shop, they scanned it, front passenger side O2 sensor is reading lean, they tighten them all up and say if it comes on just get it replaced

so I take it to a local mechanic I go to here, he replaces both right side O2 sensors, I pay 300 bucks for that and a tune up, and about 50 miles later that *****ING light comes on again, I did recently install a T.I. CAI but the light originally came on before this was on, I still have the stock MAF

can anybody point me in the right direction here?! is the T.I. intake causin me problems here? I'm sposed to leave for school next week and this car is pissing me the ***** off right now, it's been such a pain in the ass recently and I'm gettin sick of dumping money into it just to make it run, any input is much appreciated

 

[jstreet0204]

You are better off getting codes read first for free at autozone. Lean codes don't usually point to the o2 being faulty, as it looks like you have found out. Check for vacuum leaks, possibly around the throttle body where rubber sleeve goes around it. Mine wants to curl up on the bottom side some times when I put it on, and unless I check for it, it is hard to see. If you can't find any leaks try putting the stock tube back on. If you have the kind that has an eblow in front of the MAF, they tend to throw off the MAF reading sometimes.

 

[Stangboy017]

ok, i guess i'll go back to the stock intake and see if it comes back on

the weird thing is, is that it originally came on with the stock air box on there, then I disconnected the battery for a while, reconnected it, no light, drove about 50 miles, it came on, had the O2's changed, no light, drove about 50 miles and it came on again

I figured it wasn't the CAI because it came on originally with the stock air box, but who knows

 

[2000BLKGT]

IMO..it's your rear 02 sensors.

You can "turn them off", but you'll need a custom chip to do so.

It's going to cost you money, but my adivise would be to go to a qualified tuner...(I prefer SCT)...they'll run the codes to be sure...burn a custom chip for you...disarm the rear 02s and make her run a bit better.

My rear 02's didn't act up with my Bassani catted X-pipe until the 2nd year I had the pipe on...and every Stang shop I visited were surprised it didn't happen sooner.

This is typical with an aftermarket mid-pipe.

Don't waste your money putting new rear 02s in...my bet is they'll be throwing the same codes in no time...get a chip and turn them off.

 

[jstreet0204]

Get the code scanned and then let us know what it is.

 

[tomustang]

ok........ you got MIL Eliminators?

 

[Stangboy017]

went to auto zone, same code, running lean, should I just cough up the money to go to a dealer? i'm pretty pissed considering I just paid around 300 bucks and nothing has been fixed

I dont get how it could be a rear O2, the scan said it was running lean, I didnt think the rear O2's had anything to do with A/F ratio

 

[streetstang03]

this is what you need.
http://www.partshopper.com/shop/item.asp?itemid=262&catid=

/end thread.

 

[tomustang]

http://eleanor.pro3i.com/showpost.php?p=5372403&postcount=6

start reading.

 

[jstreet0204]

Rear o2's will not throw a lean code. Something else to check for is an exhaust leak.

 

[Stangboy017]

i dont get it, like jstreet is saying, rear O2's don't throw the lean code I'm getting, how does an MIL eliminator fit into this

and how come I've never come across this same issue happeneing? I spend a lot of money on the Magnaflow because I've read nothing but good reviews about it, and now I spend 300 bucks on new O2's, and i'm still SOL

this *****ing sucks, i quit

 

[jstreet0204]

i dont get it, like jstreet is saying, rear O2's don't throw the lean code I'm getting

Cause jstreet knows the the rear o2's will only trigger certain codes, and none of them are these.
P0171 System Too Lean - Bank No. 1.
P0172 System Too Rich - Bank No. 1.
P0174 System Too Lean - Bank No. 2.
P0175 System Too Rich - Bank No. 2.


There rear o2's have one function only, and that is to give a voltage reading when the eec cycles through the series of obdii tests and gets to the one that checks for cat effenciency. It will throw codes indicating that it has failed the test, or it can throw codes if the rear o2 isn't functioning.

P0420 Catalyst System Efficiency below Limit - Bank No 1.
P0421 Catalyst System Efficiency below Limit - Bank No 1.
P0430 Catalyst System Efficiency below Limit - Bank No 2.
P0431 Catalyst System Efficiency below Limit - Bank No 2.
P0156 Downstream Heated Oxygen Sensor circuit fault - Bank No. 2.
P0158 Downstream Heated Oxygen Sensor circuit Voltage High - Bank No. 2.
P0160 Downstream Heated Oxygen Sensor circuit fault - Bank No. 2.
P0161 Downstream Heated Oxygen Sensor Heater circuit fault - Bank No. 2.
P0136 Downstream Heated Oxygen Sensor circuit fault - Bank No. 1.
P0138 Downstream Heated Oxygen Sensor circuit Voltage High - Bank No. 1.
P0140 Downstream Heated Oxygen Sensor circuit Faulty - Bank No. 1.
P0141 Downstream Heated Oxygen Sensor Heater circuit fault - Bank No. 1.



The lean code can be cause by a few things.
1. You really are running lean, which may be due to the MAF reading being off, or a vacuum leak.
2. An o2 sensor that is out of range and reading high. (not likely)
3. An exhaust leak that is allowing air to seep in and mix with the exhuast and throwing off the o2 reading.

The exhuast leak sounds the most likely if the car generally runs good otherwise, and you are getting the code only on one bank, and the fact that it happend right after the midpipe install. Even a pin hole size leak can throw off the o2's.

 

[Stangboy017]

well the car has been idling goofy recently, and today when I was going to work, up a hill in 4th in low RPM, the car was pretty jumpy, thought maybe it was just bad gas or somethin, i used 87 for the first time inna long time, just to see what would happen, and ya it felt really, for lack of a better word, jumpy, kickin forward and backward, when I put the clutch in the RPM's hang and drop slow, then when I finally stop the RPM's drop all the way to about 500, then come back to about 800

maybe a leak of some sort?


and, i realize i'm probably stupid for not saying this sooner, but i was just so pissed earlier i completely forgot to mention this

 

[Jinx]

The lean code can be cause by a few things.
1. You really are running lean, which may be due to the MAF reading being off, or a vacuum leak.
2. An o2 sensor that is out of range and reading high. (not likely)
3. An exhaust leak that is allowing air to seep in and mix with the exhuast and throwing off the o2 reading.

I'd agree with #3. Especially since they told you it was the passenger side sensors. I know that the passenger side is the most difficult to seal-up when installing an aftermarket mid-pipe. I even believe there is supposed to be a gasket involved at that connection. Start there.

good luck

 

[Stangboy017]

well i gave the shop a new gasket, maybe they messed it up

 

[jstreet0204]

well the car has been idling goofy recently, and today when I was going to work, up a hill in 4th in low RPM, the car was pretty jumpy, thought maybe it was just bad gas or somethin, i used 87 for the first time inna long time, just to see what would happen, and ya it felt really, for lack of a better word, jumpy, kickin forward and backward, when I put the clutch in the RPM's hang and drop slow, then when I finally stop the RPM's drop all the way to about 500, then come back to about 800

maybe a leak of some sort?


and, i realize i'm probably stupid for not saying this sooner, but i was just so pissed earlier i completely forgot to mention this

If an exhaust leak is throwing off the o2, it can screw with closed loop operation and mess up idle. Does it run alright the first few seconds you start it up when it is cold and then get worse after a few seconds? If so this is when closed loop kicks in and would definately make me think it is sensor related, and you aren't really running lean.

 

[Stangboy017]

well i called the shop, they said when they installed it there were no leaks, and I haven't come across any clicking sounds

but i do have this weird "psssshhhhhh" as I drive along side medians or curbs, i dunno maybe it's just wind blowing over/through something on the car, but it sounds like a pssssssss

 

[tomustang]

so where's the poster codes? i don't wanna hear guesses i wanna see the code.

 

[Stangboy017]

i dont have it, autozone scanned it and said "yup, the front passenger size O2 is reading lean"

I said ok and left

I'm bringing my car back to the mechanic and going to have him check for exhaust leaks and vacuum leaks

 

[tomustang]

I spent 3 years finding out a combo of codes with the o2's all relating to the passager side. I found out it was a pulled wire out of the o2 harness. Make sure you get the code, i don't trust a autozone guys word as far as i can throw them.