Re: P0303 cylinder #3 misfire
Hmm, neat. Thanks!
"bllsht" <nospam@dot.net> wrote in message news:6fi3q2pautrue37o9cssrja8cuf5vvc8b8@4ax.com... > The FSM is a good source for repair info, but it doesn't go into all > of the details. > > The 4.0L uses a waste spark system. That is it uses one coil to fire a > pair of spark plugs simultaneously. One on the compression stroke and > the other being wasted on the exhaust stroke. One post of the coil > fires with positive potential and the other negative. > > A picture will make it easier. Scroll down to the DIS section for an > illustration of what goes on. > > http://www.motorage.com/motorage/art....jsp?id=140913 > > > On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo" > <matt@nospamplease.com> wrote: > >>Just out of curiosity, what's your source for this? I know the packs fire >>two sets of plugs but I wasn't aware it fired pos/neg, and there's no >>mention of it in the FSM that I can find. >> >>"bllsht" <nospam@dot.net> wrote in message >>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com. .. >>. For each pair of cylinders, one plug is always fired >>> negatively, and the other positively. That is, one fires from the >>> center eletrtode to the outer electrode, and the other fires from the >>> outer to the center. It's a series circuit. Open a series circuit and >>> no current flows. >>> >>> >>> >> |
Re: P0303 cylinder #3 misfire
Hmm, neat. Thanks!
"bllsht" <nospam@dot.net> wrote in message news:6fi3q2pautrue37o9cssrja8cuf5vvc8b8@4ax.com... > The FSM is a good source for repair info, but it doesn't go into all > of the details. > > The 4.0L uses a waste spark system. That is it uses one coil to fire a > pair of spark plugs simultaneously. One on the compression stroke and > the other being wasted on the exhaust stroke. One post of the coil > fires with positive potential and the other negative. > > A picture will make it easier. Scroll down to the DIS section for an > illustration of what goes on. > > http://www.motorage.com/motorage/art....jsp?id=140913 > > > On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo" > <matt@nospamplease.com> wrote: > >>Just out of curiosity, what's your source for this? I know the packs fire >>two sets of plugs but I wasn't aware it fired pos/neg, and there's no >>mention of it in the FSM that I can find. >> >>"bllsht" <nospam@dot.net> wrote in message >>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com. .. >>. For each pair of cylinders, one plug is always fired >>> negatively, and the other positively. That is, one fires from the >>> center eletrtode to the outer electrode, and the other fires from the >>> outer to the center. It's a series circuit. Open a series circuit and >>> no current flows. >>> >>> >>> >> |
Re: P0303 cylinder #3 misfire
Hmm, neat. Thanks!
"bllsht" <nospam@dot.net> wrote in message news:6fi3q2pautrue37o9cssrja8cuf5vvc8b8@4ax.com... > The FSM is a good source for repair info, but it doesn't go into all > of the details. > > The 4.0L uses a waste spark system. That is it uses one coil to fire a > pair of spark plugs simultaneously. One on the compression stroke and > the other being wasted on the exhaust stroke. One post of the coil > fires with positive potential and the other negative. > > A picture will make it easier. Scroll down to the DIS section for an > illustration of what goes on. > > http://www.motorage.com/motorage/art....jsp?id=140913 > > > On Sun, 7 Jan 2007 22:28:31 -0500, "Matt Macchiarolo" > <matt@nospamplease.com> wrote: > >>Just out of curiosity, what's your source for this? I know the packs fire >>two sets of plugs but I wasn't aware it fired pos/neg, and there's no >>mention of it in the FSM that I can find. >> >>"bllsht" <nospam@dot.net> wrote in message >>news:t1t2q2daj61omiaa6ammb7br9fs4k1te9r@4ax.com. .. >>. For each pair of cylinders, one plug is always fired >>> negatively, and the other positively. That is, one fires from the >>> center eletrtode to the outer electrode, and the other fires from the >>> outer to the center. It's a series circuit. Open a series circuit and >>> no current flows. >>> >>> >>> >> |
Re: P0303 cylinder #3 misfire
Hi all, here is an update on my 2001 TJ from a previous reply in this
thread. After replacing the broken bridge and reassembling the rocker, a test drive showed some improvement but the Jeep threw the P0302 engine code again. After several days of digging into possibilities and a few calls to Chrysler, the guys finally dug out the problem. The cam had a bad lobe on one of the number two valves. I now have a pretty much rebuilt top end, new lifters, cam, rockers, timing chain and gears, etc.. They showed me the old cam and, while the Chrysler tech wouldn't admit a bad heat treat to begin with, he did say that he has seen a "few" but they are not common to have go bad. The TJ came home today, runs great, nice and quiet, smooth at idle and driving speeds. I'm just over $700 lighter in the wallet but I should be able to run this engine til I decide I need a newer Jeep. Just wanted to let the group know the update on my problem about my misfire. Les "01XJ" <adam.tsacoumangos@gmail.com> wrote in message news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com... >I just started experiencing a rough idle on my 2001 Cherokee (78k > miles). My engine light went on a little after that with the P0303 > code. I just replaced the spark plugs, but that didn't help anything. > I was > thinking about changing the ignition coil or fuel injector. One other > possibility I was > thinking was checking the cylinder compression (maybe a gasket leak?). > Anyone have any suggestions? > |
Re: P0303 cylinder #3 misfire
Hi all, here is an update on my 2001 TJ from a previous reply in this
thread. After replacing the broken bridge and reassembling the rocker, a test drive showed some improvement but the Jeep threw the P0302 engine code again. After several days of digging into possibilities and a few calls to Chrysler, the guys finally dug out the problem. The cam had a bad lobe on one of the number two valves. I now have a pretty much rebuilt top end, new lifters, cam, rockers, timing chain and gears, etc.. They showed me the old cam and, while the Chrysler tech wouldn't admit a bad heat treat to begin with, he did say that he has seen a "few" but they are not common to have go bad. The TJ came home today, runs great, nice and quiet, smooth at idle and driving speeds. I'm just over $700 lighter in the wallet but I should be able to run this engine til I decide I need a newer Jeep. Just wanted to let the group know the update on my problem about my misfire. Les "01XJ" <adam.tsacoumangos@gmail.com> wrote in message news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com... >I just started experiencing a rough idle on my 2001 Cherokee (78k > miles). My engine light went on a little after that with the P0303 > code. I just replaced the spark plugs, but that didn't help anything. > I was > thinking about changing the ignition coil or fuel injector. One other > possibility I was > thinking was checking the cylinder compression (maybe a gasket leak?). > Anyone have any suggestions? > |
Re: P0303 cylinder #3 misfire
Hi all, here is an update on my 2001 TJ from a previous reply in this
thread. After replacing the broken bridge and reassembling the rocker, a test drive showed some improvement but the Jeep threw the P0302 engine code again. After several days of digging into possibilities and a few calls to Chrysler, the guys finally dug out the problem. The cam had a bad lobe on one of the number two valves. I now have a pretty much rebuilt top end, new lifters, cam, rockers, timing chain and gears, etc.. They showed me the old cam and, while the Chrysler tech wouldn't admit a bad heat treat to begin with, he did say that he has seen a "few" but they are not common to have go bad. The TJ came home today, runs great, nice and quiet, smooth at idle and driving speeds. I'm just over $700 lighter in the wallet but I should be able to run this engine til I decide I need a newer Jeep. Just wanted to let the group know the update on my problem about my misfire. Les "01XJ" <adam.tsacoumangos@gmail.com> wrote in message news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com... >I just started experiencing a rough idle on my 2001 Cherokee (78k > miles). My engine light went on a little after that with the P0303 > code. I just replaced the spark plugs, but that didn't help anything. > I was > thinking about changing the ignition coil or fuel injector. One other > possibility I was > thinking was checking the cylinder compression (maybe a gasket leak?). > Anyone have any suggestions? > |
Re: P0303 cylinder #3 misfire
Les,
Thanks for the follow up. Carl "Les" <wiedrick@twcny.rr.com> wrote in message news:45a45c4e$0$8920$4c368faf@roadrunner.com... > Hi all, here is an update on my 2001 TJ from a previous reply in this > thread. After replacing the broken bridge and reassembling the rocker, a > test drive showed some improvement but the Jeep threw the P0302 engine > code again. After several days of digging into possibilities and a few > calls to Chrysler, the guys finally dug out the problem. The cam had a bad > lobe on one of the number two valves. I now have a pretty much rebuilt top > end, new lifters, cam, rockers, timing chain and gears, etc.. They showed > me the old cam and, while the Chrysler tech wouldn't admit a bad heat > treat to begin with, he did say that he has seen a "few" but they are not > common to have go bad. The TJ came home today, runs great, nice and > quiet, smooth at idle and driving speeds. I'm just over $700 lighter in > the wallet but I should be able to run this engine til I decide I need a > newer Jeep. Just wanted to let the group know the update on my problem > about my misfire. > Les > > "01XJ" <adam.tsacoumangos@gmail.com> wrote in message > news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com... >>I just started experiencing a rough idle on my 2001 Cherokee (78k >> miles). My engine light went on a little after that with the P0303 >> code. I just replaced the spark plugs, but that didn't help anything. >> I was >> thinking about changing the ignition coil or fuel injector. One other >> possibility I was >> thinking was checking the cylinder compression (maybe a gasket leak?). >> Anyone have any suggestions? >> > > |
Re: P0303 cylinder #3 misfire
Les,
Thanks for the follow up. Carl "Les" <wiedrick@twcny.rr.com> wrote in message news:45a45c4e$0$8920$4c368faf@roadrunner.com... > Hi all, here is an update on my 2001 TJ from a previous reply in this > thread. After replacing the broken bridge and reassembling the rocker, a > test drive showed some improvement but the Jeep threw the P0302 engine > code again. After several days of digging into possibilities and a few > calls to Chrysler, the guys finally dug out the problem. The cam had a bad > lobe on one of the number two valves. I now have a pretty much rebuilt top > end, new lifters, cam, rockers, timing chain and gears, etc.. They showed > me the old cam and, while the Chrysler tech wouldn't admit a bad heat > treat to begin with, he did say that he has seen a "few" but they are not > common to have go bad. The TJ came home today, runs great, nice and > quiet, smooth at idle and driving speeds. I'm just over $700 lighter in > the wallet but I should be able to run this engine til I decide I need a > newer Jeep. Just wanted to let the group know the update on my problem > about my misfire. > Les > > "01XJ" <adam.tsacoumangos@gmail.com> wrote in message > news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com... >>I just started experiencing a rough idle on my 2001 Cherokee (78k >> miles). My engine light went on a little after that with the P0303 >> code. I just replaced the spark plugs, but that didn't help anything. >> I was >> thinking about changing the ignition coil or fuel injector. One other >> possibility I was >> thinking was checking the cylinder compression (maybe a gasket leak?). >> Anyone have any suggestions? >> > > |
Re: P0303 cylinder #3 misfire
Les,
Thanks for the follow up. Carl "Les" <wiedrick@twcny.rr.com> wrote in message news:45a45c4e$0$8920$4c368faf@roadrunner.com... > Hi all, here is an update on my 2001 TJ from a previous reply in this > thread. After replacing the broken bridge and reassembling the rocker, a > test drive showed some improvement but the Jeep threw the P0302 engine > code again. After several days of digging into possibilities and a few > calls to Chrysler, the guys finally dug out the problem. The cam had a bad > lobe on one of the number two valves. I now have a pretty much rebuilt top > end, new lifters, cam, rockers, timing chain and gears, etc.. They showed > me the old cam and, while the Chrysler tech wouldn't admit a bad heat > treat to begin with, he did say that he has seen a "few" but they are not > common to have go bad. The TJ came home today, runs great, nice and > quiet, smooth at idle and driving speeds. I'm just over $700 lighter in > the wallet but I should be able to run this engine til I decide I need a > newer Jeep. Just wanted to let the group know the update on my problem > about my misfire. > Les > > "01XJ" <adam.tsacoumangos@gmail.com> wrote in message > news:1167779855.090317.153570@v33g2000cwv.googlegr oups.com... >>I just started experiencing a rough idle on my 2001 Cherokee (78k >> miles). My engine light went on a little after that with the P0303 >> code. I just replaced the spark plugs, but that didn't help anything. >> I was >> thinking about changing the ignition coil or fuel injector. One other >> possibility I was >> thinking was checking the cylinder compression (maybe a gasket leak?). >> Anyone have any suggestions? >> > > |
Re: P0303 cylinder #3 misfire
I just talked to the dealer who said the heat shield had been put on
the intake to prevent overheating injector #3. I guess it rules that one out. I'll try looking at the injector this weekend. I'll wait on checking the coil since it would most likely affect 2 cylinders, although I'll keep it in the back of my head to not rule it out completely. Thanks everyone. On Jan 9, 10:07 pm, "Carl" <carlsai...@hotmailREMOVE.com> wrote: > Les, > > Thanks for the follow up. > > Carl > > "Les" <wiedr...@twcny.rr.com> wrote in messagenews:45a45c4e$0$8920$4c368faf@roadrunner.co m... > > > Hi all, here is an update on my 2001 TJ from a previous reply in this > > thread. After replacing the broken bridge and reassembling the rocker, a > > test drive showed some improvement but the Jeep threw the P0302 engine > > code again. After several days of digging into possibilities and a few > > calls to Chrysler, the guys finally dug out the problem. The cam had a bad > > lobe on one of the number two valves. I now have a pretty much rebuilt top > > end, new lifters, cam, rockers, timing chain and gears, etc.. They showed > > me the old cam and, while the Chrysler tech wouldn't admit a bad heat > > treat to begin with, he did say that he has seen a "few" but they are not > > common to have go bad. The TJ came home today, runs great, nice and > > quiet, smooth at idle and driving speeds. I'm just over $700 lighter in > > the wallet but I should be able to run this engine til I decide I need a > > newer Jeep. Just wanted to let the group know the update on my problem > > about my misfire. > > Les > > > "01XJ" <adam.tsacouman...@gmail.com> wrote in message > >news:1167779855.090317.153570@v33g2000cwv.googleg roups.com... > >>I just started experiencing a rough idle on my 2001 Cherokee (78k > >> miles). My engine light went on a little after that with the P0303 > >> code. I just replaced the spark plugs, but that didn't help anything. > >> I was > >> thinking about changing the ignition coil or fuel injector. One other > >> possibility I was > >> thinking was checking the cylinder compression (maybe a gasket leak?). > >> Anyone have any suggestions? |
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