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rough running issues
2000 I6 aw4 123000 miles. My jeep has been running pretty rough recently. Its not something new though, had a misfiring problem for like 10 months now. so here is what i have done. i had bosch platinum plugs in when it started ( threw codes p0300, p0301, p0303, p0304, p0306). plugs were black as night after 5000 miles. tailpipe is also black. (to lean?) so after reading around i switched to champion copper. worked for a week then engine light came on with codes p0300, p0302, p0304, p0305. cleared the computer thinking it didnt clear before and so far the light hasnt come back on, but the idle is still rough and i feel it misfiring. I did the seafoam twice and then water in the intake twice. smoke test and found no leaks. and cleaned the grounds to no avail. Im gonna get two upstream o2's soon and then 784 injectors. any input from you guys would be great. Thanks
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Here's a little course on what makes a plug dark-black When air and fuel burns completely and efficiently, the results are CO2 (Carbon Dioxide) and H2O (Water). Nothing more, nothing less.... neither of these has color to it. It's not much different that a fire log that has burned completely and efficiently. If you have a fireplace or enjoy camping and have seen the results of a good burn, the results are just a fraction of what you started with...white ash left at the bottom of the pit. I am sure you have also pulled black bits of log out of a pit just like you have pulled spark plugs from your engine that are black on the ignition end. The black is carbon. When carbon is produced so is Carbon Monoxide which can be lethal. 30 PPM Permissible Averaged over 8 hours 200 PPM Maximum for acute exposure 800 PPM Lethal < 2 hour exposure Carbon Monoxide is caused by partially burning fuel. In its smallest form, a fuel molecule can be compared to a fire log. If you put 1 fire log in a pit and let it burn efficiently with enough oxygen to support combustion it would leave a white ash on the outside as it burns to the core. If it continued to burn efficiently it would leave nothing but a very small amount of white ash. If you start to throw more and more logs (fuel molecules) in that fire pit you start to smother the efficiently burning log and the oxygen it was getting to burn efficiently is diminished. The fire will start to burn cooler and less efficient. The flame will lose its brightness and start to get more orange and the results will be the formation of black carbon. A Carbon Monoxide Molecule is a partially burnt molecule of fuel. If you continue to smother your log (fuel) with more logs (fuel) the flame will go completely out and leave you with Carbon Monoxide and Carbon. We cannot see a Carbon Monoxide Molecule because they are too small, colorless and order less but we do see their residuals as the black outer carbon shell they leave. Take your log out of the pit that was burning well but later smothered out and cut it in 2. What you will see is un-burnt log (fuel) in the center and a black outer shell (carbon). A partially burnt log is like a partially burnt fuel molecule. The black on your plug is the outer carbon shell. If your mixture has never burnt well, you can wipe off the black carbon and find nothing but more black carbon. If your mixture burns well at high speeds but not at idle you can pull a plug after a long ride that has a short time to idle and find carbon that can be wiped off to reveal a white residue and a clean electrode. Remember, a completely burnt log (fuel) leaves very little of what you started with... white ash (CO2 and H2O). A partially burnt log leaves most of the log with a thick black outer layer. This is why a good burning mixture leaves very little to nothing on the plugs electrode when a poorly burning mixture quickly starts to build up a black thick layer of carbon. So put more simply, the black is carbon caused by the lack of oxygen to burn the fuel completely. Although that may now seem simple, the cause(s) may not be. Causes can be: Correct amount of fuel but incorrect amount of oxygen Correct amount of oxygen but too much fuel Lack of compression to support complete combustion Poor spark to start a good combustion Cold engine temps that don't support proper vaporization |
okay, so it seems like the jeep is running to lean after reading that whole bit. Gonna replace the upstream o2 sensors. are these the correct part numbers for Upstream front and rear? NTK 23506 (R) and 23151 (F)
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Are your Champions gapped to 0.035"? As your plugs were fouled again, FYI you can also use NGK ZFR5N. Chrysler actually superseded the RC12ECC with these. They're cheaper where I live so every bit helps :thumbup1: All connections with the coil packs and the coil rail are solid? Make sure all connectors are clean with a brass wire brush and some contact cleaner. I recommend using some electrical grease on the actual mating surfaces like the top of the park plugs and on all pins: http://www.k1ttt.net/technote/antiox.html My personal favorite is SanChem NO-OX-ID Special A
Those are the correct P/Ns for "federal emissions" (single big cat). Black is actually caused by running rich. O2 sensors are still valid troubleshooting though. I could check your TPS function and the MAP. Disassemble your throttle body, clean everything gently with TB cleaner spray and a toothbrush, and set it all back together. You can reuse gaskets if you're careful and none are damaged. You should clean out the throttle body, throttle body plate, the Manifold Absolute Pressure sensor, Throttle Position Sensor area, and the Idle Air Control motor assembly. When you've got it all back together you can verify TPS function with a multimeter while the key is set to RUN (engine off, but the ECU/PCM is powered up). Backprobe the wires going into the TPS, one of them will have approximately 5VDC on it (4.98VDC, whatever). Another one is the output lead, it should be less than 0.5VDC when the throttle is shut and SMOOTHLY increase up to 5VDC when the throttle is wide open. If your TPS is jumping around or showing higher voltage at idle, the computer can think that it needs more fuel. For the MAP I'm not sure how to actually test it, but it's very important that it's clean and has good vacuum. The computer uses it as a tool to read how much air is flowing into the engine. If it thinks a ton of air is moving then in goes more fuel. Found these links regarding MAP testing. The first one is a Renix system, but the second refers to an OBD2 4.0L. Not sure if it's actually correct or if the guy copied Renix testing not knowing the difference. Worth a shot: http://www.lunghd.com/Tech_Articles/...iagnostics.htm https://www.cherokeeforum.com/f5/98g...5/#post2181997 Good luck, keep us updated |
Plugs are gapped correctly. I the throttle body looks pretty clean but im gonna take it all apart and do the sensors like you said. Hopefully it gets warm here soon. When i first start up the rpms are at 1000. And then as the jeep warms up it goes down to 500. Is that normal or could that be a sensor going bad?
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1000 for a minute or less is pretty normal at startup. Normal idle RPM is 750 so yeah 500 is quite low. Many of the same sensors can affect that (except the O2 - it's not in play until the engine warms up).
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So ill just take apart and clean up the whole intake and maybe that will help my idle. In the meantime im still gonna order those o2's and try to fix the lean problem.
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Well today was fun. Jeep ran great all day then when i went to go start it up it started shaking like crazy. Engine light came on and started blinking and the jeep had very little acceleration. I had to make it home so i drove it 2 miles and it ran like ****, but the engine light stayed solid. Once i got home had dinner, then went to start it up. Absolutely fine. Drove to autozone and had the codes pulled. P0206 and p0306. Ran fine tho just the normal rough idle ive been having. Reset the computer at home and started it up no light and it ran pretty good. Dont know what that was all about but it scared the hell outta me. O2s should be here Friday so im hoping those fix my lean problem
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Originally Posted by 70hemicuda
(Post 2279154)
Well today was fun. Jeep ran great all day then when i went to go start it up it started shaking like crazy. Engine light came on and started blinking and the jeep had very little acceleration. I had to make it home so i drove it 2 miles and it ran like ****, but the engine light stayed solid. Once i got home had dinner, then went to start it up. Absolutely fine. Drove to autozone and had the codes pulled. P0206 and p0306. Ran fine tho just the normal rough idle ive been having. Reset the computer at home and started it up no light and it ran pretty good. Dont know what that was all about but it scared the hell outta me. O2s should be here Friday so im hoping those fix my lean problem
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Originally Posted by Muaddib420
(Post 2279270)
Or if you want to be certain, you could swap it out with the number one injector
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Hmmmm you've got the 0331 head on there... hows your coolant level? You could have a very very small crack that opens more as the engine warms up, then it runs like a crippled pig. Do a compression check for us.
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No coolant loss or coolant in the oil. Check engine light has remained of and i did about 70 miles of driving today. Runs pretty good. nothing like last night thank god. This weekend im doing the o2s so ill rent a fuel pressure tester and compression tester and give you guys the numbers. Those tests aren't hard to do right?
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I can't vouch for a fuel pressure test, a compression test is super simple though.
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Well i replaced the o2s and cleaned the iac. Jeep runs pretty good now. Still gonna do the tests when i get a chance but so far she has been running good *knock on wood*
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