Suddenly, Rough Idle And A Bunch Of Codes /Shrug

[SeikenFreak]

It's a 2003 Mach 1 but this shouldn't be something specific to that. I want to summarize this the best I can to keep it short and sweet. I have a more specific odd situation and, unfortunately, the weather is BS so I can't go mess with this myself. I thought I'd ask and maybe save some time.

Codes: P0130 P1130 P1131 P1150 P1151 P1152 etc

The questions I have before the tl;dr story:
1. Does it matter which upstream O2 sensor is plugged into which plug of the harness (is there a left and right)? Maybe they are plugged in backwards?
2. Will the car throw all these codes and behave this way if NONE of the O2 sensors are plugged in? Because my other guess is that maybe I somehow yanked the main trans/O2 sensor harness plug loose when I was getting the new extension plugged in. I don't see how, I wasn't rough, but who knows.

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Essentially, reinstalled the engine a couple weeks ago, we had a brain fart and didn't think about laying out the trans harness before lifting the engine/trans back up into the car. So we were unable to get the driver's side upstream O2 sensor plugged in because the plug was no where near it.

I drove the car for a couple days and it ran perfectly. The passenger side and both rear O2 sensors were plugged in during this time. Due to some small oil leaks, I parked it in the garage, started working on it and ordered an O2 sensor extension which I figured would be easier than lowering the engine/trans to adjust the harness.

Fast forward about a week later, I fixed the oil leaks underneath and the O2 extension finally arrived. I plug it in and run the car. After idling for a bit, it starts to run rough, sounds like its down a cylinder, almost stalling etc. Eventually, it throws a check engine light with those 4-5 different codes. Sometimes, the engine will suddenly clear itself up and run completely smooth. I disconnected the MAF and the engine did change its pitch/revs but still ran mostly the same.

I just went out, wiped the ECU, let the car idle, it ran fine, and then as the car warmed up it started to idle rough and acts as if it's down a cylinder. Drive it around the block a few times, definitely feels down on power. Idle in my driveway more, still rough, tap the throttle, perfectly smooth again.. etc No Check Engine Light came on during this but it seems to take like 30 mins for it to finally trigger.

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So yea, I have no idea why all of a sudden its behaving this way. I didn't do any work around the engine except for repairing oil hoses, so it's not like I accidentally created a vacuum leak, messed up a intake gasket somewhere, or yanked some MAF/Intake sensor wire out etc.

Before anyone lists the code definitions, I already looked around online a bit and read diagnosing etc. Really just looking for answers to the questions above.

 

[SeikenFreak]

Update: I quickly messed with it some more just before the rain hit.

The problem appears to be intermittent no fuel on the driver's side?

Had the car running, started pulling ignition coils one at a time seeing if it was a specific dead cylinder. When the car was running rough, pulling any of the Driver's side coils had no affect. I was getting spark. When I pulled any of the Passenger side coils, the engine would run worse.

So.. the entire driver's side was dead.. Which now seemed familiar because this is how it was behaving when I broke down. That ended up being a snapped secondary chain on the Driver's side and hence why the engine was out (I had the head off and rebuilt as well) So now I'm thinking.. Omg.. it better have compression. So I check the compression: 220 on all four so that's good. Fhew.

So I have compression and spark. Next I star unplugging and replugging injectors, checking with test light. They appear to be getting power. If I ground out the white wire, the engine has a slight change in tone. Also, when I pulled the plugs for the compression test, they weren't fuel soaked. Looked real dry.

Finally, if you hold the RPMs at say 2k for a bit, the engine will start running normally again. At that point, if I pull a coil on the Driver's side, it'll run worse. Rev the engine up a bit again, hold RPMs, let it back down and it'll nearly stall and start running rough again.

So why is it intermittent? Is it an electrical thing or a physical fuel flow problem.. Only guess I can come up with is the car sat for a few months while engine was refreshed, it had a full tank in it, everything was fine for a couple days, I parked it in garage, had the front jacked up, and when I ran the car for a bit like that it started sucking up some gunk or something from the tank. No idea. Or for some reason the ECU is not firing the injectors on the Driver's side.. for no reason.. sometimes. I was reading 40 on the FRP at idle via my OBD2 tuner.

Update 2: Tested a couple of the injectors with a noid light while it was running rough. They are getting the signal. So it has to be a physical thing? But it's just a single rail for both sides.. I don't see how one side wouldn't get fuel and the other would.

You can literally sit there and it'll be running perfectly, then you give it a quick rev, and like a light switch, you'll feel it kill that bank and it'll run rough. After that, you can rev it and hold the RPMs for a little bit and, again like a switch, it'll pop into normal smooth operation. I just don't get it. I want to get under it and double check the O2 sensors but it's pouring rain. /riphairout

 

[snakeplisskin93]

O2 sensors by themselves won't cause these problems. You can unplug them all and car should run the same except for running a richer mixture. When a car is cold the o2 sensors are in open loop and provide a richer mixture to help heat things up. Once computer see's certain parameters are met it switches to closed loop and leaning the fuel mixture.

Sent from my SCH-I535 using the svtperformance.com mobile app

 

[snakeplisskin93]

It sounds like when it switches to closed loop your problem shows. In closed loop the computer uses all sensor data but in open loop it ignores certain sensors.

Sent from my SCH-I535 using the svtperformance.com mobile app

 

[snakeplisskin93]

It does sound like a fuel problem or fuel sensor problem.

Sent from my SCH-I535 using the svtperformance.com mobile app

 

[nxhappy]

sounds like a vac leak. check ALL lines.

 

[decipha]

it sounds like u have an x pipe that isnt set correctly in your tune

 

[SeikenFreak]

Still looking into it. Swapped the plugs for the two upstream O2 sensors and filled the tank with fresh gas Thursday night. Can anyone tell me if the passenger or driver side O2 sensor uses the green connector on the harness? One is black and one is green (the one I have to use the extension for.) I guess the O2 sensors don't have specific left/right connectors on them as they are not original.

Check Engine Light was on in the morning (was like a P1130 and P1150, I can't remember exactly) But I took it to work yesterday (roughly 20 min drive). Everything smooth in the morning. When I left work in the afternoon, I think it was running rough when I started it, but once I pulled out of the parking lot it seemed to be normal the rest of the way home.

Once I got home, I checked the codes again and it was only a P1150 now.

I did look around for vacuum leaks or loose plugs the other night. Wasn't seeing anything but I can check again and spray some carb clean around.

In terms of the tune, I'm not sure how that would suddenly cause a problem? It's a custom tune via Big Daddy Performance. Been running it on the car for years now and didn't have any issues.

Taking it to work again. Fuel pressure tester should also be arriving today. Weather looks nice tomorrow.

Thanks for the responses.

 

[Sluggie24]

Both of the O2 sensor connectors on the harness side are green on my 04 GT. The sensor connectors however are green on drivers side and black on passenger side.(bought car used so not sure if one was replaced) it will matter if you plug them in the wrong sides since the PCM adjusts each bank individually.

Unless you have long tube headers you should not need an extension harness to plug a sensor in. If you had to do that then your harness is twisted and you might be plugged in at the wrong connectors.

When you say you had oil leaks, did the oil leak onto the sensors and/or connectors? Did you look at all the wiring to make sure nothing was pinched or shorted to ground?

 

[SeikenFreak]

First: Yes I do have long tubes And I'm pretty sure the upstream O2 sensors were replaced because they look clean and new.. so probably when I got the car years ago and headers were installed. I can't remember.

Second: In terms of the oil leaks, I installed a remote oil filter and oil cooler setup. I was just getting some seepage from the lines on the new AN fittings etc. Nothing big and the only connector that got wet was the factory oil sensor there.

I was able to look at Alldata at work today and study various diagrams and connector pictures etc. The conclusion that I came to is that the Passenger Side (Bank 1) upstream connector is actually on the engine harness itself? And then the Driver's Side (Bank 2) upstream is on the trans harness (green connector).

If you use this image as a reference:

You can see three O2 sensor connections. Green, blue, and purple. Blue and purple are at the end of the harness, so obviously are the downstream sensors. The grey connector to the right is where it plugs into the main harness up above the bellhousing. That thick stupid plug is stuck up behind the engine and there isn't enough space to move it because it's wedged between the firewall and my cooling head mod crossover hose. I could probably unplug the harness but it just seems like it would suck to get it plugged back in with no space back there.

Anyway, the point of the picture is to show that the green connector is the one that is way up at the top of the bellhousing. Since I have the extension plugged into that Green plug now, I don't think I need to adjust the harness itself as I can get either plug to either side.

I'm not sure why/how the other O2 sensor connector (pretty sure it was black for me) looked as if it was on the trans harness, because it was right there and I plugged it directly into the driver's side sensor. I need to examine it again now that it won't be cold, raining and I have a better understanding. Fuel pressure tester arrived so I'll be check that tomorrow as well. (Note: I replaced the fuel pump/sending unit/filter a couple years ago/5-10k miles)

For an update on the behavior itself: On cold start it seems to have a rough/high idle for like 30 seconds and then clears itself up. Sounds like a bad misfire or something and can feel the car running rough and then it smoothes out. I took the car to work again. Worked perfectly in the morning. Then, when I took it to lunch and when I went home, both times it ran a little rough on startup and then cleared out after siting for some time or driving away. Car has power and was reving it out to 4-5k RPMs with half throttle no problem.

 

[SeikenFreak]

Worked on the car all day doing various things. Prepping for first track day of the season a week and a half away.

Hooked up the O2 sensors correctly, according to the Alldata information. I can now confirm that both upstream connectors are Green! The part that was messing me up was that there was already an extension on the one apparently. Anyway, that should be done the right way now.

Checked fuel pressure. Had 30 at the rail on startup and idle, even when it was running rough. Again, the idle just cleared itself up after 20 seconds or so. Also looked around for vacuum leaks and sprayed stuff around and didn't notice any revs.

I had the battery disconnected today for other stuff so the ECU was reset (yes, I had reset the ECU a few other times prior to this in an attempt to fix it lol.) It hasn't run rough since then. Took it for a hard drive tonight and its running solid. No check engine light yet either. /shrug

 

[15PSI]

I am glad you got your problem resolved. On Mustangs with Wide Bands, we avoid O2 extensions at all costs as they have caused many weird issues with calibrations. On newer Mustangs (Coyotes), there is enough slack present on the harness after unhooking it from the back of the engine to avoid utilizing extensions.

 

[SeikenFreak]

Ah thanks for the reply.

Yea as a follow up, everything seems to be working correctly now. For whatever reason. I'm not 100% sure what fixed the code issue, but they haven't come back since. All I did was make sure they were plugged in correctly, removed that extra extension, and reset the ECU for the 3rd time or something.

After that though the ABS light started coming on intermittently. After a couple weeks of dealing with that (and one track day), I replaced the ABS module having done some research into it. Got an ebay take-off for $120, swapped that in, and it hasn't come back.

So yea, two track days done now and everything has been holding up. Seems my cylinder head install, timing chain work, and gaskets have all been okay.