Reoccurring P0306 on 2006 TJ 4.0 stroker

[1515art]

I have been getting an occasional check engine light and running out of ideas, thus far I have replaced spark plugs, checked fuel pressure adding an in-line fuel pressure gauge, swapped camshaft position sensors, conducted an engine smoke leak test and compression checked the cylinders. The engine sensors including the 4 O2, IAC, throttle body, MAP, CPS, TPS and PCM are recently new.

the year old spark plugs I replaced did not look bad at all, cylinder 6 could have had some minor arching around the electrode. Pulling the new plugs I just installed they all look the same after 1 week of around town driving.

these are the year old plugs;

but honestly I think I’m looking to close they actually look pretty good?

the fuel pressure was right at 58#’s and stayed there racing the throttle, so I think the fuel pump is good the filters are clear and the line is not kinked.

pumping smoke into the intake with a leak tester I did not see any leak that I should be concerned about.

I had the original MOPAR cps in my newer OPDA switching in the new first cam position sensor I installed after removing the factory sensor set off a different code and the engine would turnover for at least 30 seconds without firing then suddenly startup, but clearly was not right running very smoothly with a hesitation and drop in rpm hitting the throttle? Putting in a third new crown sensor from a spare OPDA everything ran as before and the p0306 returned after hard acceleration, this hard acceleration seems to trigger the code more quickly?

I had two sets of injectors with the same random p0306 and have installed the second set of injectors in in a different order with the same p0306 so I think I can rule out the injectors also both sets of injectors are slightly different size with the same results.

I have been avoiding doing a compression test one because I don’t want to think I have valve or piston issues with the new engine, however running out of ideas I just pulled all 6 plugs again and on visual inspection they all look identical and ordinary. Checking the compression all cylinders tested at 150#’s, with s sigh of relief I can check off that box.

I have a spare crank position sensor I bought a while back but I‘m not exactly sure where it’s located on the 2006, google is sketchy on this sensor constantly cross referencing it with the cam position sensor? Also the p0306 I’m not sure the code even fits the crank sensor wherever it is?

the code is intermittent I suppose it could be a bad connection somewhere? Right after switching the larger .24 injectors with Bosch .22 and doing a hard acceleration freeway test drive the first time right after coming off the freeway and idling down I briefly got, a flashing check engine light with a multiple cylinder misfire code. This symptom has not returned now I only get the p0306 after driving a day or two or driving it really hard.

im about to return the engine to top dead center for the compression stroke and rechecking the OPDA for proper alignment but I think if is is close enough to run the PCM will force the correct cam shaft ignition timing?

the wiring is less than perfect I can continue moving things around trying to locate an iffy connection and spraying the PCM with contacts circuit board cleaner is still an option, any other ideas or suggestions?

 

[ItchyDong]

If the OPDA is out of alignment, you'd get a cam/crank correlation code. Period. It's pretty sensitive too, so if it's not there, I wouldn't fool with the OPDA at all.

Intermittent issues are frustrating. But, there are some clues that you can look at. If it were me, I'd look at live data when the code or misfire was present. The #6 cylinder is on Bank 2. I'd be looking at my O2 reading to see if it's reading more rich or lean compared to Bank 1. I'd also look at STFT to see that it's responding the opposite of whatever the O2 is reading. If Bank 2 is reading leaner than Bank 1, you've got a fuel issue. Possibly an intermittent stuck closed injector. If it's reading richer than Bank 1, you're looking at an ignition fault, or a stuck open injector. A stuck injector would peg STFT to negative numbers, and the 02 would be pegged rich (800mv).

My hunch would be it has something to do with your injectors. First off, our wiring harnesses chafe on the back side of the valve cover. These are your injector power feed, and control wires going to the PCM. If a control wire chafes, it provides a constant ground causing the fuel injector to fire out of sequence and for longer widths than the PCM desires. They cause intermittent faults regularly.

Also, beware that aftermarket fuel injectors are notoriously junk. Yes, even Bosch. Looking at injector waveforms would be an easy test, but most people don't have an oscope in the box.

 

[1515art]

If the OPDA is out of alignment, you'd get a cam/crank correlation code. Period. It's pretty sensitive too, so if it's not there, I wouldn't fool with the OPDA at all.

Intermittent issues are frustrating. But, there are some clues that you can look at. If it were me, I'd look at live data when the code or misfire was present. The #6 cylinder is on Bank 2. I'd be looking at my O2 reading to see if it's reading more rich or lean compared to Bank 1. I'd also look at STFT to see that it's responding the opposite of whatever the O2 is reading. If Bank 2 is reading leaner than Bank 1, you've got a fuel issue. Possibly an intermittent stuck closed injector. If it's reading richer than Bank 1, you're looking at an ignition fault, or a stuck open injector. A stuck injector would peg STFT to negative numbers, and the 02 would be pegged rich (800mv).

My hunch would be it has something to do with your injectors. First off, our wiring harnesses chafe on the back side of the valve cover. These are your injector power feed, and control wires going to the PCM. If a control wire chafes, it provides a constant ground causing the fuel injector to fire out of sequence and for longer widths than the PCM desires. They cause intermittent faults regularly.

Also, beware that aftermarket fuel injectors are notoriously junk. Yes, even Bosch. Looking at injector waveforms would be an easy test, but most people don't have an oscope in the box.

thank you for your reply, Just to double check without changing anything with the OPDA I brought the #1 cylinder to TDC and the alignment and marks on the OPDA were spot on.

I did run side by side graphs on my scan tool on the O2 sensors at idle but need to repeat this test during WOT, since this seems to trigger the engine light more quickly

unfortunately my wide band sensor is only on bank 1 and i have not noticed any thing unusual the values fluctuate 14.3 to 15.1 and I think this is normal different exhaust pollutants react at different values I think this is programmed in. I’m also unsure if the PCM sends different pulse rates individually to each injector or do they get the same duration pulse across all injectors?

The short and long term fuel trim is similar on both banks with the larger injectors short terms were -6 to -12 and the long term trim was -15 to -19 always on the verge of throwing a code now with a size down in injector size the values run half of the larger injectors with long term trim -9 to -12 and short term -3 to -6 but still seem the same basically in range on both banks. The differences I guess may be hard to see if this is only intermittent during acceleration or a vibration induced electrical short

the DTC has changed from system running rich to misfire on cylinder 6 with smaller injectors the first time I installed these injectors I got the same misfire on cylinder 6 and is why I took them out, but this time they went back in a different order with the misfire still on cylinder 6. This change in DTC from system running rich to the single cylinder misfire I think could be important if I can make sense of it? I was very suspicious of my fuel pump but the pressure at idle and racing the throttle look good so unless the pumps performance degrades I think it is not the issue.

still you are right it is some fuel/wiring issue, I can test pulse the injectors check the bleed down to see if they are equal but I don’t think that’s the problem. Is the O2 sensor fast enough to identify a single cylinder from the other cylinders in a single bank of 3?

 

[ItchyDong]

I apologize for the delayed and short response. I’m in the middle of an engine change at work.

Couple questions, what wide band sensor are you referring to?

Those fuel trims are psycho rich if those were observed at idle. Did you have your pcm tuned?

The pulse width varies based on inputs from multiple sensors.

 

[1515art]

I added a separate wide band O2 sensor to the number 1 bank ahead of the precat to get the real time fuel ratio and that’s where I’m getting the actual numbers I posted the range from. The fuel trims are actually where they are expected I think to be running on the ported out stroker with larger injectors and oversized throttle body on a stock untuned PCM according to the builder Chad Golen, except for the DTC my Jeep runs pretty good I just have no reference to know if it is running as good as it should?

 

[Jezza]

Trims look okay to me. ± 10% is generally acceptable for a modified setup. Do you have a large cam with the stroker. Some times that can trigger a misfire. Also check the injector clips. Occasionally they vibrate around causing an intermittent misfire.

 

[1515art]

Jezza, I’m pretty sure it has an oversized hotter cam in it but I’d have to go back to the build sheet an see what they spec out, they build a lot of engines so shouldn’t be hard to find out I could even call them if it’s not on my receipt.

If the cam is the issue I can live with re setting the code I carry a scan tool so it’s no big deal I just want peace of mind something’s not amiss potentially causing harm.

I wonder if I’d be better off with stock injectors if the computer is cutting back fuel but I’m concerned when at WOT and the computer I think at this point stops regulating the fuel ratio the same way, I might go to lean with all the extra air flow my engine has?

 

[ItchyDong]

I think you'd be better off with a tune.

Your STFT are desperately trying to remove fuel which is why they're buried negative. Once they're buried they lose their ability to vary above and below as need. It may be "normal" for a stock tune on a big build, but it's nowhere near optimal. You want your STFT numbers as close to zero as possible. I'd run a tune.

 

[Jezza]

Jezza, I’m pretty sure it has an oversized hotter cam in it but I’d have to go back to the build sheet an see what they spec out, they build a lot of engines so shouldn’t be hard to find out I could even call them if it’s not on my receipt.

If the cam is the issue I can live with re setting the code I carry a scan tool so it’s no big deal I just want peace of mind something’s not amiss potentially causing harm.

I wonder if I’d be better off with stock injectors if the computer is cutting back fuel but I’m concerned when at WOT and the computer I think at this point stops regulating the fuel ratio the same way, I might go to lean with all the extra air flow my engine has?

If it's a cam that Golen installed with the engine it should be mild enough to keep the misfire counter happy. Does it have a big lope at idle?

Out of curiosity did you resync the timing with a scan tool after messing with the OPDA? If I'm not mistaken there is a way to do that. I know on my older style cam sensor I had to do that. Even though I marked everything and was confident it was aligned it was still 7º off. Although I don't think this would cause a single cylinder misfire code, but who knows.

What is your AFR at WOT currently? You indicated that there is a wideband installed. Also have you watched the fuel trims while driving? Are they always in the 0-10% range or does it go much higher and lower. Trims work in block segments different trim values for different RPM and load cells. Sometimes they look good at idle, but under load they drift out of tolerance. Also over about 75% throttle the PCM disables the adaptive trims, therefore they have no effect on WOT.

 

[Jezza]

I think you'd be better off with a tune.

Your STFT are desperately trying to remove fuel which is why they're buried negative. Once they're buried they lose their ability to vary above and below as need. It may be "normal" for a stock tune on a big build, but it's nowhere near optimal. You want your STFT numbers as close to zero as possible. I'd run a tune.

He indicated his long and short term trims are sub 10%. That is hardly buried. IIRC the PCM can operate between -28 and +28% on the long and short terms before it hits the limit, at which point a CEL is triggered. I do however agree a tune would be ideal in getting it dialed in closer, as well as being able to adjust the ignition table.

 

[1515art]

I think you'd be better off with a tune.

Your STFT are desperately trying to remove fuel which is why they're buried negative. Once they're buried they lose their ability to vary above and below as need. It may be "normal" for a stock tune on a big build, but it's nowhere near optimal. You want your STFT numbers as close to zero as possible. I'd run a tune.

I’m sure you are right, the wide band O2 sensor I installed can connect to a laptop I might need and additional cable or something then it can be tuned remotely Chris sent me a name of a tuner that is recommended if he is available It would be worth the time and effort i think it would make a huge difference because the PCM is allowing no where near the horse power to the wheels that I think it could.

I checked wiring as best as I can and slipped new protective covers on in some places given how little room was provided for maintenance and repairs, I you went out of your way to design difficult access getting into and around the front back and many areas on the sides of the 4.0 they couldn’t have done it better, like having to remove a fender just to access a manifold bolt to tighten it the arrangement of lines, hoses, shrouds thwart every attempt at slipping a socket wrench where you need it or seeing what you doing while doing it, not completely but enough to make life difficult in a way no self respecting tractor should, lol.

If it's a cam that Golen installed with the engine it should be mild enough to keep the misfire counter happy. Does it have a big lope at idle?

Out of curiosity did you resync the timing with a scan tool after messing with the OPDA? If I'm not mistaken there is a way to do that. I know on my older style cam sensor I had to do that. Even though I marked everything and was confident it was aligned it was still 7º off. Although I don't think this would cause a single cylinder misfire code, but who knows.

What is your AFR at WOT currently? You indicated that there is a wideband installed. Also have you watched the fuel trims while driving? Are they always in the 0-10% range or does it go much higher and lower. Trims work in block segments different trim values for different RPM and load cells. Sometimes they look good at idle, but under load they drift out of tolerance. Also over about 75% throttle the PCM disables the adaptive trims, therefore they have no effect on WOT.

I don’t know the AFR at WOT on the smaller injectors but the larger ones supplied by Golen at WOT climbing a grade towing would run really rich dipping into the 9’s I have not looked since putting in the smaller Bosch injectors cruising normally it fluctuates mid 14’s to low 15’s my understanding by design to work on a range of pollutants that volatilize at different concentrations (?) not that I understand exactly what it’s doing but the flux is normal.

I don’t notice a lope exactly but it’s not completely a smooth idle Im pretty sure it is hotter than stock, how much I’m not sure? Whatever he did pulled 285hp and 330 ft#’s torque at the crank on the dyno out of the in-line 6 along with stroking porting and polishing I think the cam, pistons and the oversized throttle body are all upgraded and matched to get there. I didn’t delve into the specs of the build trusting more on Golens popularity and reputation, plus I wouldn’t know what to ask for to do it better I have to admit.

I didn’t resync the OPDA, but my concern a year ago I thought I was hearing a little noise from the crown OPDA I had swapped in a year or two before when changing it again I’d accidentally had the nylon pin in the wrong location and had to go back to top dead center realigning everything and then cross checking after with the timing marks on the flywheel. I was just double checking again to see if everything matched going back to TDC and it Was exactly lined up with the holes for the nylon pin and the position of the cam position sensor. No syncing this time or the first time I swapped it. Is this something that might help and how is this accomplished?

I’ll check the fuel trims at WOT. The shift by the PCM you describe was my concern for going to a to small of injector forcing a lean condition at WOT.

 

[1515art]

Think I may have found the answer to my misfire code, putting back in the PCM that I had tuned over a year ago just after the engine went in the Jeep runs much better, has more power and runs a little smoother the fuel trims look perfect. I think long term with only 20 miles data is looking very promising both banks are staying 0/1 range and short term +3/-3, WOT on a brief run getting onto the freeway dropped into the 13’s/1 I‘m not sure yet if it will stay there or run a bit richer pulling a long grade with a trailer, and I’m not certain how rich or lean it needs to be To keep from burning a valve but this feels about right?

I didn’t put this in before because the last time I tried it with the manifold leak i it was acting really wonky with dead spots and power surges the other 3 I’d collected all ran better the newest untuned Wrangler fix ran the best at the time, I just assumed the settings were way to far off from whatever had been done to it. I’d talked to mark about sending it back to be reprogrammed but procrastinated sending it to him now I’m happy I waited.

might be a bit early yet to totally call it fixed but looking really good so far.

 

[ItchyDong]

Think I may have found the answer to my misfire code, putting back in the PCM that I had tuned over a year ago just after the engine went in the Jeep runs much better, has more power and runs a little smoother the fuel trims look perfect. I think long term with only 20 miles data is looking very promising both banks are staying 0/1 range and short term +3/-3, WOT on a brief run getting onto the freeway dropped into the 13’s/1 I‘m not sure yet if it will stay there or run a bit richer pulling a long grade with a trailer, and I’m not certain how rich or lean it needs to be To keep from burning a valve but this feels about right?

I didn’t put this in before because the last time I tried it with the manifold leak i it was acting really wonky with dead spots and power surges the other 3 I’d collected all ran better the newest untuned Wrangler fix ran the best at the time, I just assumed the settings were way to far off from whatever had been done to it. I’d talked to mark about sending it back to be reprogrammed but procrastinated sending it to him now I’m happy I waited.

might be a bit early yet to totally call it fixed but looking really good so far.

Hmm. Seems a tune fixed it. Weird. Glad you got it figured out.

 

[1515art]

Hmm. Seems a tune fixed it. Weird. Glad you got it figured out.

Thanks but I’m not positive it’s fixed, I am optimistically hopeful based on the way it’s running at the moment… Really, I’m just guessing when the LT fuel trims were always in negative ranges and the PCM switch at WOT was dumping a considerably richer mixture at the program limits that if the O2 sensor in bank 2 is reading just slightly different not bad but enough to fool the PCM? Just a guess but opening up the throttle was the most frequent trigger it was coming on pretty quick and so far so good, no codes or pending …yet?

im curious too if my next run out to Arizona gets me an improvement in fuel economy I was averaging 11/12 on the freeway doing 65, I think there’s a little room for improvement.

I know it’s been running rich but I haven’t been sure exactly how much over, so I keep an eye on the oil for fuel in it and change the oil an filter every couple months just as a precaution, I bought 6 qts of oil, filter and a bottle of zink when they rang it up $80 seems about double what I paid last time, be good to get that under control, lol.

there’s another post here about the P0306, talks about cleaning the connections to the computer could be just swapping units might clean up a poor terminal connection for the injector. I keep 2 Velcro straps around the row of socktes to hold them secure but it could still have some corrosion?

my aim when I put the Tuned PCM in was to just see if it was drivable then then retune it and have a tuned PCM with no concern about passing SMOG although be better if it did and a factory tuned PCM as a spare.

I still need to look up and see if there is anything I can find out about running lean just to be positive I’m not switching one small problem for a much bigger one?

 

[1515art]

The check engine light just came back on but not all bad the code has changed from a P0306 to a generic P0152 O2 Sensor slow response. With the misefire on cylinder 6 codes and the generic O2 sensor slow response I’m going to swap out the down stream O2 sensor in bank 2 and kind of like I’d guessed… it’s still a guess bank 1 and bank 2 read fairly close but different enough this is probably my issue?

 

[ItchyDong]

I'm confused. A code P0152 is a bank 2 sensor 1 fault. Your graph is for for both sensor 2's (downstream sensors). The graphs show post catalytic sensors. And those downstream sensors have nothing to do with fuel delivery.

Now, on a side note: Your bank 2 catalytic converter looks like it's toast according to that graph. I can't be 100% certain, because I don't know when this screen grab was taken (closed loop, RPM, etc). But at operating temperature, the downstream o2 should look like the first picture you posted. It should be a relatively flat line post cat. When the downstream o2 sensor starts mimicking the upstream switching, it indicates that the cat is trash. (Not surprising being that you were running so rich for god knows how long. This will destroy a cat in no time.)

Your sensor 1 (upstream) o2 sensors are the sensors used by the PCM to determine STFT which drives injector pulse width.

This is a long winded way of asking... Why would you replace the bank 2 downstream sensor based on this info? Seems that sensor is working perfectly fine, it just happens to be indicating a bad cat. You need to pull up graphs for both of your upstream sensors. If you decide to post them, make sure that you're in closed loop, and that you hold the rpm slightly above idle (about 1500 rpm). Hold that rpm until an entire screens worth of data populates and then snap a pic.

 

[1515art]

I didn’t have my code reader with me when the light came on so this is just after pulling into the garage eng temp 210, at idle closed loop. I did a side by side graph of the upstream sensors and they looked pretty much the same actively moving up and down on the chart the range of movement equal between bank one and bank two, looking at the small screen on the code reader almost identical slightly different synchronization. the only difference being between the down stream sensors drawing my attention there.

I did a typo when I posted sorry it was late, the code is p0153, still the upstream sensor bank 2 then? I was confused about which one to look at so it is obviously measuring the gasses before they are treated by the precats, that makes more sense. Dumping extra fuel into the exhaust would do the cats in pretty quick I guess if it was, they don’t seem to be plugged its running the best it has since the engine went in but I guess they could be burned out without being plugged? I’ll change some sensors first and hope this solves the codes I have a spare set. I noticed the air fuel jumping for just a couple seconds getting on the freeway pretty lean 16.?/1 im not sure if that is just my combination of injectors and tune or more likely the O2 sensor response times?

But the big sign on the side of road points toward the bank 2 precat then as the most likely culprit or should I expect both precats toasted if it was that rich on fuel and this new code warning me of it running lean, I’m not sure if all this fits as the same issue or if the symptoms are just coincidental.

I have these graphs from November of 2020 just after the engine went in the precats would not have been toasted at this point they were fairly new, the O2 sensors were new I was in the process of fixing vacuum and exhaust leaks, missing engine ground straps and a host of bad engine sensors work improperly done by the shop that installed the engine, so it was hard to pinpoint where the issues were coming from.

the sensor graphs I think have not changed much?

 

[1515art]

At least I didn’t think the precats were bad unless the blown head gasket would account for just bank two going bad if the cylinder where the opening occurred was also in bank two and that could clog it?

 

[1515art]

I'm confused. A code P0152 is a bank 2 sensor 1 fault. Your graph is for for both sensor 2's (downstream sensors). The graphs show post catalytic sensors. And those downstream sensors have nothing to do with fuel delivery.

Now, on a side note: Your bank 2 catalytic converter looks like it's toast according to that graph. I can't be 100% certain, because I don't know when this screen grab was taken (closed loop, RPM, etc). But at operating temperature, the downstream o2 should look like the first picture you posted. It should be a relatively flat line post cat. When the downstream o2 sensor starts mimicking the upstream switching, it indicates that the cat is trash. (Not surprising being that you were running so rich for god knows how long. This will destroy a cat in no time.)

Your sensor 1 (upstream) o2 sensors are the sensors used by the PCM to determine STFT which drives injector pulse width.

This is a long winded way of asking... Why would you replace the bank 2 downstream sensor based on this info? Seems that sensor is working perfectly fine, it just happens to be indicating a bad cat. You need to pull up graphs for both of your upstream sensors. If you decide to post them, make sure that you're in closed loop, and that you hold the rpm slightly above idle (about 1500 rpm). Hold that rpm until an entire screens worth of data populates and then snap a pic.

Ok, I ordered one of these should be here tomorrow.

Thanks for posting the link, I don’t know enough about the precast to know if it would have been rendered chemically inactive if affected by the blown head gasket or plugged? Probably both I’d guess and overheating could have easily melted it/them a little.

Is there an average acceptable range of manifold back pressure calculation, or is it an upstream downstream % restriction measurement?

 

[ItchyDong]

Is there an average acceptable range of manifold back pressure calculation, or is it an upstream downstream % restriction measurement?

I'm guessing you're the kind of guy that can overthink a ham sandwich. Remove the upstream sensor, install the gauge. Get your cats hot. Do some throttle snaps while watching the gauge. Anything over 2.5 psi is junk.