I paid a shadetree to do the plugs…couldn’t reach the back ones with 10 blown discs Cavell, and 2 coil packs, $200
I always appreciate your help Bing, especially since you know Auroras. Any mechanic will tell you this is a very challenging car to repair. My mechanics are now friends i visit almost daily just to chat, learn about modern cars
(I was great with cars in the 70’s 80’s but no more, my first car was a balanced and blueprinted '77 Camaro Z28 with glass packs, I did all my own work in my 20’s)
Anyway, please read my latest post to George San Jose to see all the work I’ve had done, we have a new problem, code 171 since I had my serpentine belt replaced yesterday, they had to replace the motor mount that the tensioner attached to, the tensioner itself and one coil, $380 parts and labor. The code is running too lean bank 1. My mechanics think it’s the O2 sensors because we got O2 sensor fault codes last week. There are no vacuum leaks, the injectors seem fine, what’s your take? Thanks for everything
By the way, you were dead on with why it wasn’t running right, once the coils were replaced (2 of the 4) then all my misfire codes went away. The car now runs great, but after the boys replaced my serpentine belt yesterday (and the tensioner, motor mount and coil) we are getting a code 171 bank 1 running too lean.
A few weeks ago we got 2 bad O2 sensors, I never fixed these, so that’s possible. My 2 mechanics are now buddies (a Tuneup Masters owned by his dad), and they had a pain just doing the belt. We did find a slow leak at the water pump which explains why I have to top off the coolant every 3-5 days. One of them told me he once rebuilt a tranny for the Aurora and he would “never do it again!” (good thing my tranny is ok). I do, however have a nasty oil leak from the valve cover gaskets, maybe oil pan gasket too, it’s so covered with wet oil we cant tell. How “big” is the valve cover gasket job?
Hey Cavell, I found a broken wire, it began under the “beauty cover” , top left hand corner and came out to attach to a bolt on the block, my shadetree mechanic clearly broke it off when he was changing the coil packs and plugs, I can say it was no more than a 16 gauge size wire. I can send a photo of where it was mounted on the block, but i dont know where it was mounted under the cover, I wonder if it was an important wire.
Does “Pick Your Part” sell any items already pulled? I dont know how to pull O2 sensors and couldnt get to the ones underneath anyway? Thanks
If you’re convinced the oxygen sensor is bad, buy a new one
There’s every reason to think a junkyard sensor will have a bad heater circuit, be skewed, contaminated, etc.
As far as that P0171 . . . hook up a scanner
It could be bank 2 is also quite lean, maybe not lean enough to generate a P0174 code
There are many things which can cause lean codes, such as low fuel pressure, vacuum leak, faulty mass airflow sensor, etc.
A shop would perform the pcm self check first, then use freeze frame data (measured real time values of engine operating parameters) to see what conditions are causing the code to appear. In particular they’d look at the fuel trims, which are a measure of how much fuel the computer thinks it should be injecting based on everything besides the O2 sensors, vs how much it has to inject based on the O2 sensors. This discrepancy is why the code is being registered.
Presumably you don’t have that sort of real time scan-tool capability, so a visual inspection is about the best you can do. Look for vacuum hose breaks, splits, kinks, throttle body, intake manifold, egr, pcv system, injector o-rings for vacuum leaks, including loose or gasket missing on the oil filler cap or dipstick not seated. Internal engine problems and maf sensor problems can cause this too.
Since you only got a problem on bank one, start off by focusing on stuff that affects bank 1 only:
- bank 1 exhaust leaks, loose exhaust hangers, etc
- bank 1 o2 sensors properly installed and connected
- spray starter fluid in the bank 1 intake manifold and fuel injector area to see if the rpm increases, indicating a leak
Beyond that you can either try replacing the bank 1 o2 sensors , see if that helps. I’d probably seek out a pro w/a scan tool before that. They’d be able to do a quick test on the o2 sensor function w/their scan tool or other diagnostic equipment they have.
If the prior coil problem was causing a misfire on bank 1, it’s possible the cat was damaged by the misfire. This is something a shop could test by comparing the pre-cat o2 signal to the post-cat o2 signal.
One other idea, you mention you have an oil leak. if oil gets on the o2 sensor, that can cause it to not register the exhaust system o2 levels accurately and could cause this code.
Did you read my earlier comment . . . ?!
Until looking at live data, I would not make any assumptions, as to fuel trims on bank 2
I’ve seen plenty of instances where there’s lean conditions on both banks, but one was just below the threshold for setting a code
Yes , no disagreement on that point. My comment applies for the case the OP doesn’t have access to live data.
You’ve given me a lot of great info and suggestions, so you have the “tools” you need, know the following;
A few weeks ago, my entire exhaust system hit the ground, dragged 100 feet until I could clear the roadway. I’m talking about the entire muffler body, all 7 feet long and about 75 lbs. Turns out it was strapped up with baling wire when I bought it and I never noticed. My mechanic hooked it back up and strapped it far more securely.
I had to replace the intake manifold last year. The fuel code did not exist until 48 hours ago, the morning after my mechanic put in a new serpentine belt, tensioner, motor mount and a coil. He also pointed out a broken vacuum line he repaired. Based on this, the repairs that day literally caused the obd 171. He noted a slow leak coming from the water pump (which explains why I have to top off the antifreeze every 4-5 days), and tells me my primary oil leak is coming from the valve cover gaskets, but the oil on the undercarriage is so dense that he can’t tell if it’s coming from the oil pan gasket. My Aurora is idling slightly faster than I’m used to hearing, say 800, and my fuel pump is louder than normal (not grinding bearings just working harder
Hey Bing.
Almost bought the two manuals off Ebay recently, but my ability to use one is so limited. I haven’t read a wiring diagram in over 30 years (and I was in aircraft electronics in the USAF!) and I can’t do any engine work with
10 blown discs…but any help from you would be awesome. My mechanics are excellent, but I can see they have trouble with the entire Northstar layout. I think they disassembled like the entire left half of my block just to change the serpentine belt, and he’s clearly guessing on the new fuel code the OBD picked up (PO171).
I’m not poor, but I also can’t just replace unneeded parts either. The belt cost $380 when he had to change the tensioner, some coil and the motor mount.To be fair, I broke 3 belts in as many years so I knew the tensioner was shot, and he showed me how “sloppy” the motor mount was (the coil, not sure, but it did offer resistance when he moved it by hand). I can definitely use your help, you’re one of the few who doesnt reply “time to get rid of it”). I’m not in a position to, and after all the work to date, I know what I’m facing, another used car will just be someone else’s problems.
George, in what order would you chase this? My mechanics are both clearly having trouble with the Northstar layout. They did find and repair one broken vacuum line, but it was while they were replacing the serpentine belt, so the code came the next day (171). Are many of the vacuum lines visible from the top of the block or will it need to be on a lift? Do you think something happened when the muffler fell off last month? The only code we had after was the O2 sensors (2 of the 4) but they are gone, just the 171 remains. I know the spray test, good idea and easy enough…Thanks
BTW, he has a nice OBD ($5k I think he said) but it is just a handheld, he has no computers etc at the shop for “real time” if that helps you. George San Jose gave me a list of bank 1 troubles to test. I can say it’s idling slightly faster than normal (800, usually 600) and my fuel pump is louder than normal, I can hear it kick on, and it’s not the sound of failed bearings or anything, it just sounds like it’s working harder. The car is running twice as strong since we replaced the serpentine belt, tensioner, motor mount and a coil next to the power steering reservoir.
I missed your comment here, the extra noise from the fuel pump might be in play then…they did repair a broken vacuum leak the other day they found when replacing the belt. FYI, the Aurora has 4 flippin O2 sensors, and a code last month said 2 had issues, one upstream, one down. When my muffler fell off last month, it could have disconnected or damaged one of the downstream O2’s…This is kinda fun!
Cavell, was it a mistake to only replace 2 of the 4 coil packs? I had a shadetree do them to be honest, and he said he believed 2 were still good…but he also left one of the bad ones just sitting on my block after the job. I found it 2 days later while checking fluids, so he’s not the sharpest tool…I also found a broken ground wire (only about a 16 gauge, not very thick) that was bolted to the block, top left if you are looking at the cover, and the other end disappears under the cover, I wonder what that wire was grounding?
Hey Bing, to update you, i recently had all the plugs and wires changed , he also changed 2 of the 4 coil packs while he was at it. On Wed, my mechanics replaced my serpentine belt, the tensioner, the motor mount that they connected to and one coil (I don’t know which, it was below the power steering reservoir. He did tell me my AC compressor was tight when he moved it by hand, but I just replaced that a couple of years ago, and my AC works just fine. It only blows cold on the passenger side, but I’m sure that’s just the blend door, and I can’t afford the labor to pull the entire dash, nightmare job.
I desperately need your help with the electrical Bing, here is the list;
The cruise control is dead, it worked intermittantly for a few months then died
All interior lights are dead, every one, including the exterior side lamps
Power mirrors, dead
Drivers side power seat, dead, just the part that moves it forward and back, the lumbar stuff works
The gas gauge is intermittent. it will “turn on”, bounce around and stop, but that’s been so for years
My dash lights take a few minutes to kick on at night, but they always activate eventually.
If you were looking at the fuse box by the drivers left knee, the entire row on the far right (numbers 16, 12, 8 and 4) won’t light my test lamps, fuses known good. These are all "interior lamps and exterior lamps and perimeter lights, so we have an idea where to begin, yes? I would tell you I had a history of leaving my windows down and rain surely got into the inner door, this may explain the power seat and mirrors since the controls are on the drivers door. I would really like my interior lights back and my cruise control (it helps with 10 blown discs) Where can I start with the cruise control? Since it worked on and off, is that a clue that it’s the switch or some sending unit? How about the fuse panel, I saw no damage at all behind the fuse panel (wiring). Thanks
Yep. There is a specific procedure to change the belt in the service manual. There is about a 2" square opening at the splash panel that you feed the belt through. That’s why it takes an hour to do it, part of it laying on your back. When I had the shop change it, I brought the service manual with so they could read the procedure, and while they grumbled about doing it, was happy to see the procedure.
I’m not big on electrical and have trouble reading a schematic so I mostly bumble on looking for clues. It sounds like you might have a ground issue since more than one circuit is affected. Most of the main circuits are in the box under the rear seat though. I had a problem with the door lock and traced it to a particular wire by running a temp wire from under the seat. Problem was there was no room to feed a new wire through the door.
I understand your reluctance but I gave up on ours when the fuel pump went. I got $100 from the junk yard when they hauled it away and I got my garage stall back. And that was with good glass, engine, trans, sheet metal and interior. I understand tight funds but you can lease with a warranty for a couple hundred a month.
Did I say I hate wiring? Some people hate plumbing but I hate both. For cruise I guess I would suspect a switch issue and maybe unrelated to the rest. If the cruise light comes on especially and you just can’t engage it. If the light comes on, there is power getting to the unit.
For all of the other stuff, like I said I’d suspect a ground issue. I took a look at the book and there are at least ten ground connections and a bunch of other ground splices. The ground splices are all wrapped inside the harnesses so that would be very difficult to deal with unless you knew for certain there was a bad splice. There is at least one behind the dash but it didn’t look like that ran to the systems you are having trouble with. I guess I would start at the battery under the seat and follow the ground (black) wires where ever you can to make sure they are clean and tight. Also there should be several under the hood that need to be checked. It would be better to focus on one particular circuit though and maybe get lucky, or run a new ground wire to by pass the whole bunch.
Sorry but I never really liked that car. My wife picked it out because of the styling and color and it was a nice car to drive, but was a beast to work on. Remember that old country song, “thank God and Greyhound, she’s gone”? The car, not the wife. We agreed that anything she buys should have a warranty.
If the mechanic had a scanner that cost 5K, it can DEFINITELY display real time data
If he’s got a pro-level scanner like that, he should hopefully know how to effectively use it and perform proper diagnosis.
Has he hooked up his smoke machine to look for vacuum leaks yet?
If there’s a split or disconnected vacuum hose/line, he’ll find it REAL fast using the smoke machine
based on the fact your fuel pump is noisey AND the gas gauge is intermittent, there’s a strong possibility you need to replace the entire fuel sending unit, which consists of the pump, float and sock
as far as the fore/aft seat motor, is it getting power when you push the switch?
If not, does it move if you manually supply 12V yourself . . . ?
What about the exhaust . . . did your mechanic secure it with proper exhaust hangers?
If in doubt, take it to an exhaust shop, and they’ll take care of it for a reasonable price