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This was weird. ‘05 sat for a few weeks while I tweeked on a couple non-related odds and ends(bumper paint and alt replacement).
Go to warm it up this morning and it idles fine, let it run for about 5 mins while I bolt in the bumper and feed the pups. Hop back in and notice it’s sputtering, heavy rotten egg smell too.
I turn it off to get ready for work and try one more time, this time taking it for a quick run down the block. It runs fine but gets a heavy sputter, almost backfire, again then the blinking CEL at an idle, heavy egg smell still. Putter it back in then let it sit.
put the code reader on it a few hours ago.
It warmed up with no misfires, then sputtered again when it got warm, maybe 160*. I saw cyl’s 4 & 5 misfiring pretty bad and others were good except for a few counts on another cylinder.
I then swapped coils to cyl’s 1 & 2 and it stopped misfiring altogether. Let it idle and took it for a quick run around the hood and it never counted another misfire, still smells like egg though.
Seems to pull fine though there is a slight sputter and can’t say it accelerates as smooth as it probably should.

Bad cats ya think?

Haven’t checked back pressure or cat temps. Vacuum was a steady 26 mmHg or so at rev and fuel trims look real good when warm, within 2%. What’s also weird is that the cats is working according to the rear O2, with a steady .7V at both.
 

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This was weird. ‘05 sat for a few weeks while I tweeked on a couple non-related odds and ends(bumper paint and alt replacement).
Go to warm it up this morning and it idles fine, let it run for about 5 mins while I bolt in the bumper and feed the pups. Hop back in and notice it’s sputtering, heavy rotten egg smell too.
I turn it off to get ready for work and try one more time, this time taking it for a quick run down the block. It runs fine but gets a heavy sputter, almost backfire, again then the blinking CEL at an idle, heavy egg smell still. Putter it back in then let it sit.
put the code reader on it a few hours ago.
It warmed up with no misfires, then sputtered again when it got warm, maybe 160*. I saw cyl’s 4 & 5 misfiring pretty bad and others were good except for a few counts on another cylinder.
I then swapped coils to cyl’s 1 & 2 and it stopped misfiring altogether. Let it idle and took it for a quick run around the hood and it never counted another misfire, still smells like egg though.
Seems to pull fine though there is a slight sputter and can’t say it accelerates as smooth as it probably should.

Bad cats ya think?

Haven’t checked back pressure or cat temps. Vacuum was a steady 26 mmHg or so at rev and fuel trims look real good when warm, within 2%. What’s also weird is that the cats is working according to the rear O2, with a steady .7V at both.
I'm not an expert in this category and it's hard for me to relate to you since I have no cats and I'm running e85 but I will offer some suggestions.
I would first suggest maybe trying to adding some fresh fuel. I know you said the car has been sitting for a few weeks but how long has it been since you fueled up? It's possible that maybe it's just bad fuel. If you wanted to get anal about it you could disconnect the fuel line at the engine bay and route that into a fuel bucket via hose. Then remove the fuel relay in the engine bay fuse box and use a wire to hot wire the fuel pump to run and drain the fuel.
How, many miles does the car have? If you don't have a lot of miles then I doubt that your cats would be clogged.
You could also possibly have dirty injectors with built up crud, which could also be related to bad gas. It would make sense cause it sounded like it improved the more you drove it, (maybe loosened up some gunk)?

If it's not related to fuel then the only other possibility I can think of is the maf not working 100% correctly throwing off the mixture causing it to be rich causing the sputtering and smell. But, this would most likely throw a code.
 

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I would have said to pull your plugs and check them, but you swapped around coilpacks and it went away... seems pretty obvious it was an ignition problem. Might want to replace the coilpacks that you swapped around, or at least see if you can have them tested.

Your cats were probably overwhelmed with raw fuel. If the misfire symptoms are gone and your ignition checks out, take it for a good run on the highway. If it still smells then maybe you need to replace your cats.
 

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Discussion Starter #4
Good ideas y’all. I had just gased up before it sat. It’s been my 2 mile a day commuter for about 4 months now.
I’ll pull plugs tonight and check MAF readings also, forgot to do that last night. It’s been cleaned but I always suspected it was acting up because of how it pulls. It was summer then and chalked it up to the hot air k&n and ecm pulling timing.
It has 101K on it now and don’t know if it’s been modded before. It’s bone stock aside from the K&N.
Gonna give it a go now & hope for the best.
Thx
 

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This was weird. ‘05 sat for a few weeks while I tweeked on a couple non-related odds and ends(bumper paint and alt replacement).
Go to warm it up this morning and it idles fine, let it run for about 5 mins while I bolt in the bumper and feed the pups. Hop back in and notice it’s sputtering, heavy rotten egg smell too.
I turn it off to get ready for work and try one more time, this time taking it for a quick run down the block. It runs fine but gets a heavy sputter, almost backfire, again then the blinking CEL at an idle, heavy egg smell still. Putter it back in then let it sit.
put the code reader on it a few hours ago.
It warmed up with no misfires, then sputtered again when it got warm, maybe 160*. I saw cyl’s 4 & 5 misfiring pretty bad and others were good except for a few counts on another cylinder.
I then swapped coils to cyl’s 1 & 2 and it stopped misfiring altogether. Let it idle and took it for a quick run around the hood and it never counted another misfire, still smells like egg though.
Seems to pull fine though there is a slight sputter and can’t say it accelerates as smooth as it probably should.

Bad cats ya think?

Haven’t checked back pressure or cat temps. Vacuum was a steady 26 mmHg or so at rev and fuel trims look real good when warm, within 2%. What’s also weird is that the cats is working according to the rear O2, with a steady .7V at both.
A steady .7v at the rear O2's means you are dumping a LOT of fuel... Running extremely rich. The egg smell is also a sign of being extremely rich. What do the front O2 volts look like? Be willing to bet when you did the Alt, you either left a ground wire off, or busted a ground wire for the front O2's. Rears should stay about 0.5v and once the cats are hot, when they change, it should be much slower than the fronts.
If there isn't an issue with a ground, having 101k miles, I'd replace both upstream O2's
 

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A steady .7v at the rear O2's means you are dumping a LOT of fuel... Running extremely rich. The egg smell is also a sign of being extremely rich. What do the front O2 volts look like? Be willing to bet when you did the Alt, you either left a ground wire off, or busted a ground wire for the front O2's. Rears should stay about 0.5v and once the cats are hot, when they change, it should be much slower than the fronts.
If there isn't an issue with a ground, having 101k miles, I'd replace both upstream O2's
i thought the front o2s were case grounded, unless you're talking about the heater circuit ground.

i also don't think there is a ground near the alternator... it itself is grounded to block, has 1 positive main to the battery and then the F and L terminals.
 

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Discussion Starter #7
Yeah - haven’t gotten back under the bonnet but good observation nonetheless on voltage readings. I’m pretty sure the fronts were flopping back and forth but the torque app probably doesn’t show the frequency like a scanner would, front O2 might be getting lazy.
still might stand to reason that the cat might not be as efficient as it should due to being clogged but still not enough to throw a code.
going to check plugs, cat temps, back pressure and sensors(visual & scan) next.
 

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Discussion Starter #9
Ah - will do, I did unplug that when messing with the alt. It’s plugged in but will double check it
 

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Discussion Starter #10
Quick update after some more tinkering. I have some extra parts that are known good so I swapped plugs(NGK TR55’s) and a newish Delco sensor on bank 2 - same results as far as rear sensor voltage at idke(.7vish) but sputter isn’t as bad.
the burns and frustration may make me want to think it sounds better but the sputter has nearly gone away - no misfires.
I also did check cat temps and when at 2k rpm post cat temp was at least 100* hotter.
with fuel trims in line, I suspect the cats to be partially clogged. I ordered a back pressure gauge and will check that when I get it.
Any other ideas - sputter em out.
thx
 
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