Random Misfires 2 and 6

[dscott90000]

So far over the last 500 or so Miles I have received a misfire cylinder 6 code that was pending and now just recently a misfire on cylinder 2 that is also not confirmed just pending.
Note: the cylinder 6 misfire code disappeared

Only other code I have is a P0138 that is confirmed bank 1 sensor 2. The truck also smells a little fumey as well and has a random idle drop and the occasional shut off .


What I've done :

Changed plugs to Autolite coppers
changed oil
sea foamed
cleaned IAC and Throttle body very well.

Oil looks doesn't look milky and I am getting decent mpg

 

[ltd02]

Only other code I have is a P0138 that is confirmed bank 1 sensor 2. The truck also smells a little fumey as well and has a random idle drop and the occasional shut off.

O2 sensor can cause all kinds of issues. Sounds like it's running rich. I've gotten misfires from them before. I'd just swap it and see if things get better. Shouldn't be too difficult to replace as it is a downstream.

 

[dscott90000]

Which sensor is the bank 1 sensor 2?

and would this sensor being bad really cause a misfire? and fumey smells from exhaust... other things can cause 02 sensors to throw codes as well correct?

Its just a little baffling that a sensor can mess these 3.7 liters up like this.

Has any gone cat less and reported better running etc?

 

[ltd02]

Which sensor is the bank 1 sensor 2?

and would this sensor being bad really cause a misfire? and fumey smells from exhaust... other things can cause 02 sensors to throw codes as well correct?

Its just a little baffling that a sensor can mess these 3.7 liters up like this.

Has any gone cat less and reported better running etc?

Bank one sensor two is the drivers side downstream (after the cat). Bad O2 sensor will confuse the heck out of your fuel/air mixture and can easily cause a misfire. I just had this happen over the summer to my 11 Avenger (3.6L Pentastar). Bank 1 sensor 1 high voltage and it was violently misfiring at times. I was getting a P0300 and some other O2 specific codes (PO132). I saw the high voltage on my scanner but figured it was something else since it was bucking so bad. I went and changed it (NTK also for that one) just to see if it would do anything and haven't had a problem since. I had the foul smell and CEL (sometimes flashing) as well and actually feared for the cat.

I would try to change yours and see if it helps. I think a bad upstream sensor is actually worse but I'm not claiming to be an expert. Just passing on my recent experience.

 

[dscott90000]

Ok I appreciate your input. I had 3 different 02 sensor codes at one point and replaced all 3 but the upstream on the drivers side ...could this possibly be the culprit and not the downstrea
m? Even though the code is for bank 1 sensor 2

 

[ltd02]

Ok I appreciate your input. I had 3 different 02 sensor codes at one point and replaced all 3 but the upstream on the drivers side ...could this possibly be the culprit and not the downstrea
m? Even though the code is for bank 1 sensor 2

It's possible that the "new" 1/2 sensor was bad. I'm hoping you used either Mopar or NTK. The one I changed on my Avenger only had 58k on it. I would definitely change the one giving the code but if the one you didn't change is original (not sure of your vehicle particulars) might not be bad to swap that out and complete the set. The 1/2 reading being high means its sensing the rich mixture but apparently can't correct if you smell the unburned fuel. Could be 1/1 or a fuel delivery issue if the sensors don't fix it. Might want to have the fuel pressure checked too. Nice to be able to see live data and watch the sensors cycle.

 

[CactusJacked]

Which sensor is the bank 1 sensor 2?
and would this sensor being bad really cause a misfire? and fumey smells from exhaust... other things can cause 02 sensors to throw codes as well correct?
Its just a little baffling that a sensor can mess these 3.7 liters up like this.
Has any gone cat less and reported better running etc?

Sensor 2 is a post cat (downstream) sensor, and it monitors the efficiency of the catalytic converter. It's the pre-cat (upstream) O2 sensors that monitor the air/fuel.
So no, a bad downstream sensor won't cause a misfire, but it will trip an error code.

 

[ltd02]

Sensor 2 is a post cat (downstream) sensor, and it monitors the efficiency of the catalytic converter. It's the pre-cat (upstream) O2 sensors that monitor the air/fuel.
So no, a bad downstream sensor won't cause a misfire, but it will trip an error code.

Figured the upstreams would be more likely to cause issues like this. Troubling thing is that the misfires are on the other bank anyway.

If you seafoamed the intake, did the op change the plugs before or after the seafoam treatment?

Cat going?

 

[ltd02]

I'd still be suspicious of that upstream sensor you didn't change. If the downstream is reading high and it stinks, it seems logical the upstream should be high as well. You can't add fuel after the upstream sensor and I don't believe they are that different as far as detection sensitivities if they are different at all. I've heard the connectors are not the same but don't know if this translates into a difference in detection levels. In fact all four sensors are the same on my Avenger with the exception of one having a different part number because the wires are longer. Really need the Mopar experts to chime in here. I do believe I am over my head at this point. First step is admitting you have a problem. :shrug:

 

[dscott90000]

Changed plugs before sea foam

 

[ltd02]

Changed plugs before sea foam

More relevant to the pending misfire. So you've never really thrown a true misfire CEL, just pending? Sounds pretty random. I usually use Motorcraft PM3 cause I have it on hand for a different vehicle that is prone to carbon knock, but I've heard it and Seafoam can foul the plugs. Most people recommend changing the oil after but I've also heard some claim the plugs can foul from that stuff too.

Have you ever overheated?

 

[dscott90000]

Not me personally in my 1 month of ownership.
The idles pretty low as well. And there's some clacking going on at 2 000k-3k rpms ... it only seems to do it around these rpms . Seems like there is a knock somewhere too.

The sound of the motor revved isn't too nice once it passes the 3 k or so mark.. but once it gets passed that it smooths out... then does the same metal on metal sound on the downshift / when the vehicle slows back to 2500-3000 rpm. So random pending misfire codes , and an 02 sensor code. My dome lights are flashing occasional as well...

Valve job?
Lifter issues?

 

[ltd02]

Might be time for a visit to a shop for a careful diagnosis. Sounds like there are many issues going on here and too difficult to diagnose from afar. Many of your issues could be related... or not. You could have valve, lifter or timing issues (usually a chatter or ticking) or since you mentioned a knock it could be low end. You also may have some electrical issue on top of this. I'd check the battery and its connections for the electrical stuff first and then I'd take it for a checkup. It will likely be worth a few bucks to find out what a professional thinks is wrong instead of just throwing parts at it. I'm beginning to wonder if its been overheated and things are starting to go south on you.

 

[dscott90000]

I'm thinking I have a bad ground and it's screwing everything up. Where's the best place to add a new ground from motor to frame etc. My mechanic had to cut my neg battery cables and only added on from battery to alternator or the compressor. Also can't I take off the valve covers and inspect for bad lifters springs etc? When you say "low end" ??Also let's say I wanted to keep this jeep for ever...what's a standard rebuild on these 3.7s

 

[MarkJ]

Clamp a jumper cable from the neg terminal on the battery to a good clean unpainted grounding point on the engine and go for a ride.

 

[ltd02]

I'm thinking I have a bad ground and it's screwing everything up. Where's the best place to add a new ground from motor to frame etc. My mechanic had to cut my neg battery cables and only added on from battery to alternator or the compressor. Also can't I take off the valve covers and inspect for bad lifters springs etc? When you say "low end" ??Also let's say I wanted to keep this jeep for ever...what's a standard rebuild on these 3.7s

Do what Markj said about the ground.

You can definitely pull the valve covers and have a look. Not sure if you'd be able to tell much given no full code. Sometimes its even hard to see a busted valve spring and you'd have a full code if that had happened, but wouldn't hurt to look and see how things are under there. Check for any sludge while you are in there.

And low end would be a rod knock. TwoBobsKJ has a great example in one of his threads. Not unusual if you overheat these things and dump some coolant in the oil. Mine is slowly intensifying after I overheated a few years ago. Waiting for the spun bearing. Rebuild prices will vary depending on where you live. Might be easier to find a good running donor or buy a reman engine.

 

[dscott90000]

Eh god dam jeep . Why did they get rid of the 4.0.

 

[dscott90000]

Aright I'll report back once I tinker a bit. I've got a rebuilt title and 135k on the dash. Could this be wrong since it's a salvage \ rebuilt title

 

[ltd02]

Good luck and keep us posted. I've never owned a 4.0 Jeep but know plenty of people who have and heard they were tough motors.

The 3.7 is a great motor if taken care of and not overheated. They can run strong for hundreds of thousands of miles but it's always a crap-shoot when you get an unfamiliar used vehicle and even more so when its a salvage. I have no idea what the disclosure regulations are on selling a salvaged vehicle. I'm guessing as long as it's listed that way on the title that's all you get to know. So it's sort of "as is" and I'm guessing the odometer reading may be irrelevant.

 

[dscott90000]

Ya its still a very good jeep and the transmission is a good one, Mercedes I believe . Any one know why they changed the transmissions out after 2002