2003 50th Anniversary Convertible 59K miles, I purchased from a friend who took it in on a trade for a Hot Rod. I needed something to piddle with and the price was right. The car has a Vararam intake, BBK short tube headers and a Billy Boat axle back exhaust, factory H pipe still in place. I also think a 160 degree thermostat was installed as the temp rarely goes above 165 while driving and stays below 180 at idle. The check engine light was on when I purchased, codes were P0134 and P0154 (O2 Sensor related). Seller provided 2 new sensors. It's out of character for me to purchase a vehicle with mods but they seemed to be quality mods from proven names so I took the chance.

Problem: I replaced sensor 1 in bank 1 and bank 2 as the codes indicated, cleared the code and after a couple of drives the same codes returned. I figured the new sensors were provided so nothing to loose in the simple fix option. Where to go next? There are many threads that indicate the Vararam system plays hell with the emissions system, as I didn't install the mods I have no idea if a tune accompanied them when they were installed. I'm thinking I need to find someone who can tune car to the correct specs as to not trip the check engine light. My county requires emissions so can't register the car until I find a solution.

The car drives great otherwise, accelerates and shifts perfectly. Only other symptom is the rich exhaust smell which I'm sure is related to the O2 sensors/check engine light.

Any advice is greatly appreciated...Also, I'm in the Chattanooga TN area so a good tuner rec would also be appreciated.

 

I'm sure C5Diag will chime in but you need to find out if you have powers and grounds to the o2s and also your signal wire. Do you have a scan tool to read what the O2s are doing?

 

First thing I'd find out if the P.O. had these DTC's pop up soon after his header installation...any exhaust leak upstream of front O2 sensors will drive those sensors lean and the PCM will schedule more fuel (closed loop only and a false lean O2) so that is probably the rich smelling exhaust symptom you have...also these aftermarket headers will cause all kinds of O2 sensor issues especially the LT's !!...also what brand O2 sensors were installed ??...if not OEM that would be suspect too....usually bad O2 sensors cause 90% of these DTC's...I would also check the O2 heater function...if you have a scan tool you just watch the O2 sensor Millivoltage with key ON...should drop from 450 mV to below 200 in 2 minutes I believe...you can buy one of those cheap amp clamps at Harbor Freight and put it around either wire of the heater circuit...you should see around 1.5 Amps and if not working the car will stay in "open loop" at idle until you raise the RPM to like 3000 RPM...the car will usually go into "closed loop" in roughly 1 - 1.5 minutes give or take with a good heater circuit...yes, I'd find out if a tune was done...if so I can't help with the diag...let the tuner fix I!!...you really need a scan tool to look at those O2's and your fuel trims....now you can have a lean condition (P0171/P0174) which can set an O2 low activity DTC such as yours but only if the long term fuel trims have not exceeded 23% so no 0171/0174 set...so it's NOT always the sensor that's bad just because a DTC says "O2 SENSOR" in it like this one doesn't always mean it's that part that is bad !!

 

C5 Diag...Thanks for the quick response, unfortunately I have no access to the owner that had the mods put on the car. I think I'm going to take it to a local speed shop that comes well recommended and does tons of LS1 work and let them see what they come up with with their scan tools. I'd rather get it done once correctly then me and my amateurish skills playing the hit and miss game. Frustrating because it runs great but I know that adjustments are needed because it is definitely running rich.

Thanks again

 

Sounds good !!...keep us updated as to what the fix was...it may help other Forum members with the same issues...Good luck !!

 

Great recommendations C5 Diag!!!!!!!!!!

 

Follow up (hate it when threads have no resolution or ending) Took the car to In Tune Motorsports in Charleston TN (Scott is the owner) Turns out the O2 sensors I was provided by PO were bad (brand was MostPlus, should have been a red flag but they were free). Replaced with OEM sensors and tuned accordingly. Scott said the car had a previous tune that was done well but needed some tweaking. Low end was rich and high end was lean. Long story short...car is fine, codes are gone and passed emissions this morning. Thanks for all advice given...moral of the story, don't trust cheap aftermarket O2 sensors and if you have bolt on mods that weren't done by you, it's worth the peace of mind to let a good tuner look at the car to make sure everything is as it should be. I've never seen a tuner at work and it was an eye opener as to all the systems that can be accessed and manipulated to change the dynamic of the car.

 

Great to hear !!....moral of story....”DON’T BUY AFTERMARKET SENSORS” !!

 

"Scott said the car had a previous tune that was done well but needed some tweaking. Low end was rich and high end was lean" Pffft! A tune that is low end rich and high end lean is NOT a tune that was done well! He was trying to be nice to a previous tuner. Glad he got you straitened out though.

 

Again, the whole "tune" world is very foreign to me. Scott mentioned that the car seemed to be set up for an aftermarket cam which is no longer present. Car runs great and passed emissions so I'm happy