11 mpg

quicksilvr · Post by **quicksilvr** » Wed Feb 13, 2008 9:37 pm

I just got 11mpg on my last tank of gas. Me thinks something is wrong.

After installing my 2.5" stainless exhaust (it got installed behind a FF long tube header, 1 upstream O2 in the #2 header pipe, no cat, no downstream O2), I reset my stock '00 ECU, and pretty much right away threw code 0171. Previously, I woudln't throw any codes, except an 0140 if drove on the highway, and even with the code driving on the highway, I could average 29-31mpg.

So obviously 0171 is dumping a TON of fuel. I could have told you it was running rich just from the smell, but I wouldn't have guessed I was going to only go 130 miles on a whole tank. It's so bad that even if I turn the car off and COAST into the garage, the whole garage smells like uncatalyzed exhaust for a couple minutes.

Any suggestions?

03blackrt · Post by **03blackrt** » Wed Feb 13, 2008 9:42 pm

Suggestions? Get Megasquirt!

Whats code 0171? EDIT: Nevermind, I looked it up.

INVUJerry · Post by **INVUJerry** » Wed Feb 13, 2008 9:49 pm

I guess try getting a new 02 sensor maybe.

quicksilvr · Post by **quicksilvr** » Wed Feb 13, 2008 10:23 pm

03blackrt wrote:Suggestions? Get Megasquirt!

Whats code 0171? EDIT: Nevermind, I looked it up.

That was my first thought.

And it totally depends on how much tax money my wife and I get back....if any. If we owe, then the MS idea is screwed for a while.

invujerry wrote:I guess try getting a new 02 sensor maybe.

That was my other thought, but I wanted to see if anyone else thought it was a decent idea before I spend good money on a new one. I'm thinking about going ahead and installing a second downstream bung, using the non-fouler trick and plugging in another O2. But that's even more work and money. arg

Post by **occasional demons** » Wed Feb 13, 2008 10:38 pm

By #2 header pipe do you mean the primary tube, as in it's only reading 25% of the exhaust output? Could be why the PCM thinks it's lean, dumping fuel. I think if you get a bung in the collector or after the header it will improve. Just my humble opinion.

aperson · Post by **aperson** » Wed Feb 13, 2008 11:47 pm

^^^ Do what he says. Or replace the sensors.

Adionik · Post by **Adionik** » Wed Feb 13, 2008 11:48 pm

Same here. I'm throwing the same code and I can smell the gas at idle.

Damn LTH's

gilly02le · Post by **gilly02le** » Thu Feb 14, 2008 1:58 am

just use the non-foulers, they are a couple bucks a piece and will work perfectly, as i used to have the same problem.. i also bought my o2 sensor for eBay , i think its a borg warner, anyways, its been good for 15,000km now, no CEL.. so dunno, its worth a shot for ya, plus i only paid 37 dollars for the sensor... think the eBay user was Evalero.. just thought id share my .02c

BlackRoseRacing · Post by **BlackRoseRacing** » Thu Feb 14, 2008 6:07 am

What brand O2 sensor are you using for the upstream?
Do you have the correct upstream O2?
2000 models have there own Upstream and Downstream while the 01/02 models are different. If you have an after market Bosch O2, have the place you got it from check to see if there listing shows that same O2 sensor for the 2001/02 model. If it comes up as the same sensor, its the wrong sensor...

2000 Neon
5269866 - Upstream
5293037AD - Downstream

2001/02 Neon
5269868AB - Upstream
5033039AA - Downstream (Fed emissions)

I wold start with the above first....
P0171 - Fuel system LEAN
Even though he is getting a reading off of one cylinder, that cylinder should still give a correct A/F reading to the O2 sensor. And if he is getting 11mpg to the gallon, either that cylinder is running lean all the other 3 are rich as hell, or that cylinder is functioning properly and the O2 sensor is not giving the correct reading to the pcm.
If it really mattered which cylinder the O2 sensor was in, they all would be mounted into the collector Vs one primary tube....

Post by **occasional demons** » Thu Feb 14, 2008 7:46 am

It has to affect it some what otherwise I doubt GM would waste the expense of putting one in each bank on their dual exhaust vehicles.... My theory is that it isnt getting any input for that 720* of crank rotation, causing the PCM to think it's lean, but like I said it's theory...

quicksilvr · Post by **quicksilvr** » Thu Feb 14, 2008 9:32 am

thanks for the PN's BBR. I'll check into that today. I'm about 95% sure that the sensor I currently have installed in the upstream is a replacement Bosch from when I first bought the car and replaced both sensors. The car was in stock form at that point, and I just replaced them as insurance and normal maintentance.

turbodudey · Post by **turbodudey** » Thu Feb 14, 2008 1:27 pm

occasional demons wrote:It has to affect it some what otherwise I doubt GM would waste the expense of putting one in each bank on their dual exhaust vehicles.... My theory is that it isnt getting any input for that 720* of crank rotation, causing the PCM to think it's lean, but like I said it's theory...

EGO correction isn't really that fast though. And even at idle you still have an ignition event on that cylinder every thenth of a second or so. I don't think the LTH is the problem...

Dave, did you fill up the fuel tank before this happened? Or was someone else driving your car? Also, are you sure all the unburned fuel you're smelling is gasoline?

If somehow the tank got filled up with alcohol, that would certainly make it run lean.

quicksilvr · Post by **quicksilvr** » Thu Feb 14, 2008 2:12 pm

Here's another big thing I forgot to mention. When it threw the 0171 code, it started idling rough, like it had a huge cam with tons of overlap. Plus the engine runs rougher even off idle....revving freely or under load when driving, it's not as smooth as it's always been in the past. At idle, it almost feels like it's missing....and then I can still feel the "miss" as the revs climb. By about 3500, I can't feel it or hear it anymore.

I'm wondering if something else went belly up. I'm pulling the plugs this afternoon (I've been putting it off because I don't a have a socket). If the plugs all look good, then I'm stumped.

EDIT: Yeah, the plugs are as black as midnight. There was enough fuel residue on them that I could light them with a lighter and they'd burn for awhile. I don't even want to drive it when it's running this rich....because it's gunking everything up.

BlackRoseRacing · Post by **BlackRoseRacing** » Thu Feb 14, 2008 7:14 pm

throw out the Bosch O2's and get the Chrysler one's.....

quicksilvr · Post by **quicksilvr** » Fri Feb 15, 2008 9:28 am

Another update: I reset the ECU last night when I pulled the plugs and cleaned them all off. Driving home after working on the car (it's a 4 minute drive through town) the car ran smooth and normal. Idle normal and smooth, revs normal.

This morning: Car was in the garage over night, so it was ~60 degrees for startup. Immediately after startup, it started idling really lumpy again, like it has a huge cam or something. When I stopped at one stoplight on my way to work, I shut it off and checked the codes. NO CODES! So it's idling horribly and has not yet thrown a code.

I am going to get a new O2 sensor today, but besides that, does anyone have any other ideas? I'm pretty sure that today with it running poorly it will throw code 0171 again. But it doesn't make sense now, because I assumed it threw the code, and THEN started running rich and like crap. Turns out it starts running like crap before it even throws that code. I'm confused.

gilly02le · Post by **gilly02le** » Fri Feb 15, 2008 10:12 am

dirty injector? improper fuel pressure... It does sound like its the o2 sensor.. my car ran like that when i had the stock upstream go bad.. car would idle really heavy, and would turn my back bumper black in no-time...plus id get about 250km to a tank instead of 450...

quicksilvr · Post by **quicksilvr** » Fri Feb 15, 2008 7:39 pm

I ordered a new O2 today, PN#5269866. $120something retail, but I ordered it through wholesale parts and got it for $74 delivered to me at work through our account with the dealer. I hope it's the problem.

kc2005ptgt · Post by **kc2005ptgt** » Sun Feb 17, 2008 9:23 pm

I think you need to get a downstream o2 on there as well Dave, and run that non-fouler mod!!!!

Post by **occasional demons** » Mon Feb 18, 2008 4:48 pm

gilly02le wrote:dirty injector? improper fuel pressure... It does sound like its the o2 sensor.. my car ran like that when i had the stock upstream go bad.. car would idle really heavy, and would turn my back bumper black in no-time...plus id get about 250km to a tank instead of 450...

I was thinking that, too, but the 0171 is a lean condition code. Causing the PCM to add fuel because it thinks there is a lean condition. It's either the o2 or the placement of the o2. If the FPR went bad or an ijector was dumping fuel, then the PCM would throw a rich condition code and try to lean the mixture. being that it's that rich I would think that the o2 isn't picking up on it or the PCM isn't getting the message from the o2.

quicksilvr · Post by **quicksilvr** » Mon Feb 18, 2008 7:30 pm

occasional demons wrote:
gilly02le wrote:dirty injector? improper fuel pressure... It does sound like its the o2 sensor.. my car ran like that when i had the stock upstream go bad.. car would idle really heavy, and would turn my back bumper black in no-time...plus id get about 250km to a tank instead of 450...
I was thinking that, too, but the 0171 is a lean condition code. Causing the PCM to add fuel because it thinks there is a lean condition. It's either the o2 or the placement of the o2. If the FPR went bad or an ijector was dumping fuel, then the PCM would throw a rich condition code and try to lean the mixture. being that it's that rich I would think that the o2 isn't picking up on it or the PCM isn't getting the message from the o2.

It's running rich right now, and has not yet thrown a code. Which tells me the O2 is just shot, and unable to regulate a proper AFR. That lean code I got before was most likely because the AFR was varying to both extremes due to the sensor not working correctly.

Post by **occasional demons** » Mon Feb 18, 2008 11:31 pm

I hope the o2 does the trick, having to drive my Cherokee, because the other guy's insurance (Westfield) hasn't gotten off their tired ass, is killing me. I have put $70 in it since the 12th. I feel your pain....

Adionik · Post by **Adionik** » Tue Feb 19, 2008 1:42 am

How can you run the non fouler if there is no room to plug the sensor in the bottom LTH 02 hole?

snkmug · Post by **snkmug** » Sun Apr 13, 2008 6:47 pm

what was the verdict? My car is doing the exact thing, P171, engine revs up and down, sounds like its camming at idle...will go to redline with the car in neutral.....help!!!!

Adionik · Post by **Adionik** » Thu Jun 26, 2008 1:46 am

Any updates?

Jerome Adams · Post by **Jerome Adams** » Thu Jun 26, 2008 7:58 pm

sounds just like what my car just did...only mine got real loud. Turns out the upstream O2 had vibrated out and was laying next to the pipe... 0171 and strong fuel smell. I would put money on the upstream being bad. Sounded like it was cammed cause the pulsing exhaust out the O2 bung.

I have the OBX LTH and was able to get a downstream in after extending the wires about 18" ...but just barely. It is a tight fit, but if you push the heat shield over as far as possible and kind of pull on the pipe a little ...you can get it in there.