imgn tht

2004 coupe with Blackwing, catted LT's, ghl exhaust. Started it up for the season a few weeks back and ran very poorly. Wanted to stall out when stopped and in drive. Worried I got condensation in the fuel lines as I somehow didn't realize I only had 1/2 tank of gas while it sat for the winter. I poured some Techron in the gas tank and also found a worm clamp between the MAF and cai completely loose. Proceeded to clean MAF (off car with crc mass air flow cleaner) , TB (on car with tb cleaner) , and tighten all clamps and the silicone coupler. Ran better after all this but still not right. No longer wanting to stall, but idle is still lumpy (like I have a mild cam) and running very rich. Haven't seen this much black soot coming out of the exhaust ever. Side effect of Techron?

Next steps I did was look for exhaust leak. Headers were tight to heads, and all connections post O2 sensors looked clean.
Codes currently thrown are PO131 and PO171.

I pulled the all the plugs and they were solid black. Changed all plugs with same kind (a.c. Delco iridium 41-110) and new wires (Taylor Thundervolts). No real difference.

I have a new O2 sensor on order for the driver's side upstream...in the header, hoping that cures the PO131. Assuming it too is loaded with carbon buildup for some reason.

Still need to check for vacuum leaks, though I replaced the pcv line off the passenger valve cover to the tb as that line showed some cracking on the end.

I feel I've done most of the common fixes. Only things I haven't touched are fuel filter (2004 is in tank so I can't replace?). Pcv valve is under valley cover or doesn't have one??? Cracked valve spring...is that a stretch? Test MAF for faulty, will be doing soon. Figure out possible vacuum leak.

What else could be causing the rich conditions and choppy idle?

neutron82

if you clear the codes do they immediately come back?... do you have headers and if so were they installed recently?... there isn't a lot of room to work with where the o2 sensor wires are routed and it's very common for them to get melted by the headers and cause o2 codes to pop up

04zjimc

I would replace both O2s sensors..code 131 i believe is misfires probably caused by the O2 sensor..

neutron82

p0131 is low voltage bank 1 sensor 1 (driver side front) which could be caused by damaged wires to that sensor, that's where I would start

imgn tht

The headers were installed about 2 years ago. I wrapped the wires and connector away from the collectors and was under there today to look at the area. No damage to the wires or connector. All tied up away still. Looked to see if the connector had loosened up, but was still clicked together.

I had sprayed the TB cleaner in the TB and it went into the intake while cleaning. Would that cause any long term issues? The next time I started the car after that it didn't want to start the first and second time. Then it came back on the next try and hasn't been an issue since. Could that have caused the PO131?

Codes don't come back right away after clearing. But maybe the next 1-2 drives. The last time I drove it the CE light flashed and then went solid. I cleared it and drove about 5-10 miles and the CE light did not come back. Was started at least 3 times since (while at trans shop, just moving around lot/lift) and the last drive also about 5-10 miles I got no CE light, but is was getting rougher idle at stop signs the longer I drove.

foggy

I would also suspect that your fuel has gone bad...
Techron won't help that situation
You could have enough moisture as well to cause issues.
Did you put in some sort of stabil before you stored it for the winter???
If not, I'd think about getting that fuel out.. And getting fresh NO Ethanol fuel in

imgn tht

I'm pretty sure I put a bottle of stabil in, but the more I scratch my head at the cause of my issue, I'm worried I may not have. It was a busy time of year for me and I ended up driving it more than I thought I would after I considered it "in storage". Hence having only 1/2 tank left once I started it this year. I have no idea how to get the old out now and I've since topped it off when I added the Techron. Could it be that I'll just need to burn through all the gas that's in there? Interestingly enough it's gotten better since I filled it up, less codes, doesn't want to die at stop signs, but still running rough at times.

The new O2 sensor is on the way, so if that doesn't resolve it, I may have to look more at the gas.

foggy

I would try to burn more gas out of it before you put in new O2 sensors..
The bad gas may contaminate the new ones..
Try to burn out at least 1/4 tank more and add fresh in.. See what happens then.
Just don't push it hard until it's running normal..You dont need to complicate problems.
Take it out for a nice 100 mile cruise or something

imgn tht

Thanks, will look to burn more fuel out of it.

04zjimc

how was the car running before you stored it? My o4z was stored with a half a tank of fuel also..it sat for afew months started it up ran like ****..i too thought bad gas but in my case 2 broken spark plugs wires..and they were no old at all. So just check everything. My car ran great before i stored it.

imgn tht

Ran perfectly fine before storage.

C5 Diag

Would you consider yourself an advanced DIY'er ??...131 is O2 sensor low voltage bank 1(upstream sensor) and 171 is lean bank 1...do you have a scan tool ??...you need to look your upstream O2 sensor waveforms and your fuel trims...if the 02 sensor is reporting LEAN (low millivolts) your fuel trims (long and short term) will be way positive...your rich condition...let me know if you can do this and maybe I can help...if your O2 sensor is reporting a lean condition you can spray some propane or carb cleaner into your brake booster line and see if the O2 sensor now reports rich (higher millivoltage)...at least you'll know if your O2 sensor is working properly...upstream sensor should be oscillating between 100-900 millivolts if operating normally...a shorted control sensor wire could be driving the sensor lean !!

C5 Diag

it's NOT the fuel filter so don't bother changing that...if you think you have a vacuum leak you can spray some carb cleaner around all your vacuum lines...a vacuum leak WILL give you a lean bank 1 DTC...then that will drive your fuel trims way positive and there is your RICH condition !!...bank 1 is drivers side so concentrate on the left side with your leak !!

imgn tht

I'd say mild DIY'er. I've installed all my mods myself, and have worked on cars sporadically my adult life. But when it comes to technical stuff, I'm not as comfortable and don't have the proper tools to measure. I do not have a scan tool either.

Glad to hear you don't think fuel filter, was reading about the process today and wouldn't be something I'd want to tackle.

Still need to do more to look for vacuum leaks. Can't be the loose oil cap could it? Also getting both PO171 and PO174 regularly now. Drove it at lunch today to burn off some fuel and within an hour they came back 3 times (I cleared it shortly after it threw the CE light each time). No more PO131, but picked up PO300 again.

Thoughts on injectors being clogged or simply a bad maf? New plugs and wires installed over the weekend, no change.

04zjimc

unplug the maf and see if if runs better..

imgn tht

I just read one way to test for a bad maf was to unplug the harness with the car running. If the car continues to run, it is a sign that the maf is bad. Is this correct?

I just tried it and my car continued to run and stayed just as, if not slightly worse with the rough idle. And the smoke coming out the exhaust was heavy. Airing out my garage now (detached, in case anyone is worried about the family inhaling fumes).

So could that be it?

04zjimc

i would try clean it first..

imgn tht

Cleaning it was actually the very first thing I did back when this all started. I can try to do it again, but wondering now if it isn't just bad. What about electrical connections/fuses for the maf? Anything there to check before I source a new maf?

C5 Diag

Hi,
Without a scan tool you are probably just "guessing"...NOT a loose oil cap...P0300 is a generic misfire code...not cylinder specific....the P0174 is bank 2 lean so now you have BOTH banks lean...DON'T drive the car too long with these codes or will will CERTAINLY burn up your cat's !!....very expensive...my recommendation is bring it to a shop or buy yourself a scan tool...I have a small Actron but I just upgraded to an Autel MS906 which is bi-directional and will do everything but brush your teeth !!...since you are throwing the left and right bank lean I'd spray the carb cleaner on both sides of the engine near any vacuum lines...a smoke test is the gold standard for finding leaks but since your tooling is limited you're kind of sunk. If it is a vacuum leak the car will run better at higher RPM's ...looking at your long and short fuel trims would point this out definitely....I'd say buy a scan tool for a few hundred !!...keep me advised !!...oh, and if you smoke cigars you can smoke test with that...blow smoke into the brake booster hose !!

c6miller

Same thing happened to me last year. The car ran very rough and wanted to stall.I think there was enough condensation in the tank to make the engine run poorly. I filled up with fresh gas and Techron and it was better in short order. Try that before you start throwing away your $$ on new parts