Air Fuel ratio at 10.0 before and after chaning O2 sensors, smelling like rotten eggs - Dodge SRT Forum
 
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post #1 of 15 (permalink) Old 05-14-2019, 04:55 PM Thread Starter
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Air Fuel ratio at 10.0 before and after chaning O2 sensors, smelling like rotten eggs

Hello so on my 05 SRT4 I have changed both O2 sensors with brand new Bosch sensors (CEL codes were on before and after change... yes after clearing the codes as well... they would pop back up), catalytic converter was recently changed out done at a local shop, and as well I changed today the Temperature sensor with a factory Mopar sensor and factory Mopar sensor connection as well. (Changed it out because a CEL code appeared and the connection was broken as well) But there are still 2 symptoms: the exhaust still smells like rotten eggs and the AF ratio is still at 10.0 (maximum rich.) I remember someone told me on a previous post that the Bosch Sensors arent good enough and I should put NTK O2 sensors instead? Because theyre factory? Thanks in advance for the help!!! Feel free to ask any questions
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post #2 of 15 (permalink) Old 05-15-2019, 09:04 AM
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Use OEM O2 sensors. The upstream O2 sensor is the one that matters, it tells the PCM the air/fuel ratio. The downstream isn't important, it just tells the PCM if the cat is working. What else is done to this car? Where is your wideband sensor?



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post #3 of 15 (permalink) Old 05-15-2019, 09:23 AM
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The Bosch narrowband sensors used to be known for having a slightly different response curve than the NTK sensors like what was used stock. While I'd prefer the NTK sensors, the Bosch ones shouldn't be causing the car to run pig rich.

Have you tested fuel pressure to the rail to make sure the pressure regulator hasn't gone bad and is providing too much pressure? If you have the stock fuel system with a 2005 car you can get an in-line adapter since the stock fuel rail doesn't have a Schrader test valve on the '04+ cars. I thought AutoZone used to carry these as part of their loan tools so it might be worth checking. (Just be careful about removing and not bending the stock nylon fuel line that goes from the firewall area over the engine to the rail. As the cars age there's a chance they will get brittle and you don't want to break is as I think they're discontinued new from the dealer.)

If you have access to a scan tool or something like a DiabloSport that can display live computer data, you can also see what the short-term and long-term fuel trims (STFT and LTFT) are reading. If they are all max negative values that might back up the idea of a mechanical problem like too high fuel pressure or a stuck injector, showing the computer is reading the O2 sensor data ok and is trying to pull (reduce) fuel but can't take enough out.

Eric H. - '04 Neon SRT-4 (eBlue/S2) - '92 Dodge Daytona IROC R/T
'91 Dodge Spirit R/T - '19 Pacifica Hybrid Limited - '14 CTS-V Wagon
'08 Cobalt SS Turbo - '14 Cruze Turbo Diesel - '02 SVT Focus (S/C)
'04 SVT Focus (EAP) - '07 Ram 1500 - '81 & '85 Chevy Citation X-11
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post #4 of 15 (permalink) Old 05-15-2019, 11:50 AM Thread Starter
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I don't know if my car has a wideband sensor or not... I thought the O2 sensors are the ones that work as wideband sensors? (If you buy em and install them of course)
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post #5 of 15 (permalink) Old 05-15-2019, 11:56 AM Thread Starter
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Yeah from what I know the window sticker in the front says "Cobb" so I'm guessing at one point the previous owner had it Cobb tuned, maybe he just never gave me the Cobb Access port. Also, it has a Injen Turbo Timer. I've been trying to get it to work... I can adjust the AF ratio BUT once I turn off the engine and turn it back on the AF ratio goes right back to 10.0... as well I cant get the turbo timer to work either. I've followed all of the instructions on the Injen website pdf. So yeah those are the two major things I think that have to do with like tuning and stuff.
But yes most likely I will have a mechanic I know hook it up to a fancy scan tool so he can tell me what's wrong with it (if the O2 sensors end up not being the problem, I already ordered them from Rock Auto) because I think my scan tool may let me see some live data but honestly I aint too trained in this and have no idea what to look for lol

Last edited by Hamlet; 05-15-2019 at 12:01 PM. Reason: Additional info
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post #6 of 15 (permalink) Old 05-15-2019, 12:35 PM
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The stock engine uses two oxygen sensors, one right off the turbo housing/exhaust manifold before the catalytic converter and a second downstream O2 (oxygen) sensor after the cat. They are both narrowband, which means they accurately measure oxygen levels to determine air/fuel ratio only at the stoichiometric point, or ~14.7:1. They can only tell the computer if the car is richer or leaner than that point.

The computer uses the upper O2 sensor to adjust fuel enrichment at idle and partial load cruising conditions that are around the 14.7:1 air-to-fuel ratio they can read. When you go into boost the computer runs calculations off pre-programmed tables to determine how much richer it needs to run for safety and to prevent knock. The computer learns if the car needs slightly more or less fuel at light load cruising conditions and can apply a corresponding adjustment to the fuel applied under boost or during wide-open throttle, but can't use the stock narrowband O2 sensor to verify.

The downstream O2 sensor after the cat isn't directly used for fuel calculations. It's primarily used to verify the efficiency the catalytic converter is operating and make sure it's in a safe operating range.

If the car has a third, aftermarket wideband sensor installed, it would be used to drive a gauge showing the actual air/fuel ratios since they can measure across a wide-range, generally from 8 or 10-to-1, so if you're watching a wideband showing 10:1 that may be as rich as it can read and the car could actually be running much richer than that. Note that some wideband O2 kits install their sensor in place of the upper stock O2 sensor, than provide a simulated narrowband sensor output from the wideband gauge/controller to feed the stock computer.


It sounds like you recently picked up the car and don't know much about the history. If that's the case, it's possible the previous owner pulled some or all parts off. If the computer has an aftermarket tune that doesn't match the hardware installed (i.e. expecting different fuel injectors, MAP (manifold absolute pressure) sensor, etc.) it won't run correctly.

When you say you adjust A/F and then it resets, what exactly are you adjusting? Some old turbo timers displayed A/F if tapped into an O2 sensor output, but most turbo timers (that keep the engine running a short period of time after it is shut off) would have nothing to do with air-fuel settings. Back when the cars were new and before the computers could be tuned (reprogrammed) owners used to install piggyback fuel controllers like the APEXi SAFC and others that slightly altered the MAP sensor reading to trick the computer into thinking there was more or less pressure in the intake manifold, which then allowed for less or greater fueling.

Eric H. - '04 Neon SRT-4 (eBlue/S2) - '92 Dodge Daytona IROC R/T
'91 Dodge Spirit R/T - '19 Pacifica Hybrid Limited - '14 CTS-V Wagon
'08 Cobalt SS Turbo - '14 Cruze Turbo Diesel - '02 SVT Focus (S/C)
'04 SVT Focus (EAP) - '07 Ram 1500 - '81 & '85 Chevy Citation X-11
'90 Pontiac Turbo Gran Prix (ASC/McLaren) - '93 Olds Achieva SCX W41
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post #7 of 15 (permalink) Old 05-15-2019, 01:09 PM Thread Starter
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Thanks for the info! I'm so sorry I meant Apexi Turbo Timer (not Injen). I believe it's pretty old but yeah it seems to let me change the AF ratio settings but when I turn off thr car and turn it back on yeah it resets. I remember when I took off a old O2 sensor I saw it had a extra wire crimped onto it.
And yes I just bought the car about 1 month and half ago, but I remember I randomly took a picture that had the AF ratio gauge in it the first day I bought ut and it was still at 10.0. And it has been smelling like eggs since I bought it as well

And no I havent tested the fuel pressure regulator yet but I'm going to the dealership today to pick up a wastegate solenoid I ordered so I'll ask if they have the fpr and if it's under $100 I'll buy it

Last edited by Hamlet; 05-15-2019 at 01:44 PM.
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post #8 of 15 (permalink) Old 05-15-2019, 02:29 PM
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If it's the stock fuel system, the permanent filter/regulator assembly is at the tank. Just in case you happen to have any Stage 3 or modified filter/regulator installed now, I wouldn't throw it away if you replace it. I'd still suggest measuring fuel pressure first before throwing parts at the car.

For the air/fuel, if the Apexi Turbo Timer is attached to a the stock narrowband O2 sensor the computer uses it's pretty much worthless. The narrowband O2 sensors can only accurately ready the air-fuel ratio (AFR) at ~14.7:1, so without a wideband O2 sensor and wideband gauge, you're just getting a guestimate.

If you can smell it that bad it very well could be running that rich or possibly even worse. The only way to tell would be to install a wideband or if you dyno the car and the dyno operator can measure it at the tailpipe.

I'm trying to remember off memory if there were any variants of the Apexi SAFC (Super Air Fuel Controller) that were integrated with a turbo timer. Assuming you have one, if it keeps resetting that might indicate an internal battery backup for the settings has gone bad, but I don't think they have one though, so that would mean it might not be getting constant power with ignition off to keep it's memory.

Either way you should remove it and put the car back to stock. You'll want to verify which injectors you have, which MAP and TIP sensor you have (TIP = throttle inlet pressure; also used to measure atmospheric barometric pressure), make sure none of the wiring is hacked, no "MAP clamps" installed, then verify you have a stock tune. If you don't know what tune is installed you probably want to have the computer flashed back to stock and tune from there after everything is running perfectly.

Eric H. - '04 Neon SRT-4 (eBlue/S2) - '92 Dodge Daytona IROC R/T
'91 Dodge Spirit R/T - '19 Pacifica Hybrid Limited - '14 CTS-V Wagon
'08 Cobalt SS Turbo - '14 Cruze Turbo Diesel - '02 SVT Focus (S/C)
'04 SVT Focus (EAP) - '07 Ram 1500 - '81 & '85 Chevy Citation X-11
'90 Pontiac Turbo Gran Prix (ASC/McLaren) - '93 Olds Achieva SCX W41
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post #9 of 15 (permalink) Old 05-15-2019, 02:48 PM Thread Starter
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Alright yeah I'm most likely gonna have a mechanic I know give it a good inspection this week to figure out why it smells like eggs and why it's at 10.0. I'll definitely share the info you have told me with him (like to test the fpr, and that the Apexi Turbo Timer seems to be useless) I'll also ask him if it needs Wideband sensors or not (because I mistakenly already ordered the NTK sensors yesterday)
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post #10 of 15 (permalink) Old 05-15-2019, 08:15 PM Thread Starter
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Hey Blackbird I have 1 last question before I stop posting 50,000 posts in 1 day... would you happen to know which solenoid is the Wastegate solenoid on the Solenoid Bracket? Because I changed what was supposedly the wastegate solenoid with a Mopar one from the dealer and after changing it I cleared the code but the code popped back up 5 seconds later. I kinda expected this as the solenoid doesn't have a vacuum line to the wastegate actuator... while (I believe) the one on the very left does have a vacuum line from the solenoid to the wg actuator. (theres 3 solenoids btw) So yeah do you think maybe the dealership has the wrong part names in their computer? Because I went back today and I verified that they supposedly gave me the right part. He showed me the part number I bought and showed it was indeed a WG Solenoid. But yeah as mentioned maybe the dealer is wrong? And I should get the solenoid that has the vac line that goes to the wastegate actuator?
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post #11 of 15 (permalink) Old 05-19-2019, 12:22 AM
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It should be the green, #2 solenoid for the WGA boost control. The 2005 PL (Neon) parts manual shows 04606599AA but the last letter may have changed if they updated it. You should still be able to download a copy of the factory service manual from one of the sticky threads at the top of the "How To" section here on the forums. The solenoid diagrams are under the "Exhaust System and Turbocharger" section.

Which code is coming up for the boost problem? If it isn't building boost correctly the car shouldn't be dumping extra fuel, so that's likely not why it could be running super rich. The manifold absolute pressure (MAP) sensor on the intake manifold pressure how much pressure and air is going into the engine and determines how much fuel is needed.


By the way, the stock computer can only use narrowband O2 sensors. If you want a wideband O2 sensor you'll need to get a kit with a wideband gauge that mounts in the car. That will show you the actual air/fuel ratio. Even if the stock narrowband sensor the Apexi should be tapped into can't measure air/fuel accurately, if it's showing a solid 10.0:1 it probably is rich.

Before dumping more parts on the car you really should have someone familiar with the SRT-4 go over the car to see if there's anything obviously broken or modified, but if your mechanic doesn't specialize in them I'd start with checking fuel pressure and then use a scan tool to check the fuel trims to see if the computer is trying lean the car out but can't due to wrong injectors, fuel pressure too high, etc.

Eric H. - '04 Neon SRT-4 (eBlue/S2) - '92 Dodge Daytona IROC R/T
'91 Dodge Spirit R/T - '19 Pacifica Hybrid Limited - '14 CTS-V Wagon
'08 Cobalt SS Turbo - '14 Cruze Turbo Diesel - '02 SVT Focus (S/C)
'04 SVT Focus (EAP) - '07 Ram 1500 - '81 & '85 Chevy Citation X-11
'90 Pontiac Turbo Gran Prix (ASC/McLaren) - '93 Olds Achieva SCX W41
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post #12 of 15 (permalink) Old 05-19-2019, 11:01 PM Thread Starter
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The CEL code is P0243 Turbocharger Wastegate Solenoid A... yeah thanks for letting me know about the solenoid diagrams I'll definitely check them out right now, theres a chance that I may have put some vac lines in the wrong places or who knows. But yes I have an appointment tomorrow with a mechanic, I'm pretty sure he isn't a specialist in SRT4s but hopefully he can narrow down the problem. Also I found out recently that BOTH the AF ratio gauge and the Turbo Timer are ONLY connected to the battery. They have no signals connected to them. Only a power source. Lmao. So this problem has gotten even stranger... but yeah hopefully tomorrow the mechanic can somehow see if the AF ratio is correct or not and adjust it accordingly (if that's even the problem) but yeah idk if I mentioned this or not but I installed both NTK o2 sensors and about 70 miles later the o2 sensor codes have yet to pop up! So yeah those codes are gone so thats something else to not worry about.
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post #13 of 15 (permalink) Old 05-20-2019, 04:38 AM
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Yeah from what I know the window sticker in the front says "Cobb" so I'm guessing at one point the previous owner had it Cobb tuned, maybe he just never gave me the Cobb Access port.
As far as i am aware, COBB has never offered tuning options for our cars.

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Also I found out recently that BOTH the AF ratio gauge and the Turbo Timer are ONLY connected to the battery. They have no signals connected to them. Only a power source. Lmao.
you may have mentioned this earlier, but what kind of A/F gauge are you using? is there a sensor in the exhaust somewhere for that gauge?

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yeah idk if I mentioned this or not but I installed both NTK o2 sensors and about 70 miles later the o2 sensor codes have yet to pop up! So yeah those codes are gone so thats something else to not worry about.
thats a good step in the right direction!


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post #14 of 15 (permalink) Old 05-21-2019, 08:20 AM Thread Starter
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The AF ratio gauge is Hotsystem brand. But yeah as mentioned earlier I believe it's just connected to the battery for show and tell. It is currently sitting in a mechanic's shop and I'll update you guys with what the mechanic finds is the cause of the smell
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post #15 of 15 (permalink) Old 05-21-2019, 08:34 AM
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The AF ratio gauge is Hotsystem brand. But yeah as mentioned earlier I believe it's just connected to the battery for show and tell. It is currently sitting in a mechanic's shop and I'll update you guys with what the mechanic finds is the cause of the smell
ah ok... that is a shitty $24 narrowband a/f gauge. It doesnt even come with its own sensor, it taps into the wiring for the stock sensor. Those things are essentially a fancy light show at best.


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