Jeepwalker
Well-Known Member
- Messages
- 973
- Location
- WI
Gents, Love to hear your thoughts on this recent issue (H3 2007, I-5, 200k mi):
Been having a 'miss' where she bucks at times between 52-62 mph ...and pretty much ONLY during longer flat-road cruising periods, or even a bit worse if the road is a slight incline (when engine is under a higher load, before it wants to downshift). Usually at around 1,825 RPM. Please see misfire graphs below. Let me know if you have any ideas. Sometimes it never chugs ...all day or a couple days. Sometimes under the right conditions it may do it a fair amount and once it starts it tends to do it quite a bit (again, on flat cruising between the speeds listed above). But if I kick it down a gear it stops 'chugging'.
Note: I don't feel any 'misses' outside of the 52-62 window during, nor are there any misfires (by real-time scanner) during: Acceleration, deceleration, and very few at speeds outside the window I listed above. The vehicle has not set any misfire codes ..so its below the misfire threshold. HOWEVER, the total misfire counts in a 50 minute test you can see in the first chart below (upper Rt hand corner). Obviously Cyl #4 has something going on. #4 misfire condition was appx the same before and after I swapped coils (but didn't change plug orientation (which I will put a new one in it's place). Iridium plugs are about 4yrs old. I pulled the coils and plugs. Did not see anything visually. I ohmed them out ....will research my readings tomorrow. One coil ohm readings did seem way off, but oddly it is Cyl 5 below. Not a particularly high misfire cylinder. The plugs seemed fine by eye & ohm reading. As I mentioned, I replaced the plugs in the same orientation, but reversed the coil locations to see if the misfires would change to the new locations. They didn't. Compression is: #1=137psi, 2-5=150psi.
I replaced the MAF sensor a few days ago with a GM (OEM) sensor, as I noticed the Air Intake Temp was 'off' even after cleaning. I did buy a new plug for #4, and will install it to see if that changes anything. What I find interesting is that all cylinders pretty much spike at the same time. Although when they do, #4 has many more misfires ..but it seems to do it during the time they all do. Also I noticed for whatever reason the fuel signal periodically spikes?
What do you think? Possible idea which come to my mind are: Check Grounds, Check alternator output (battery is new BTW, recently charged up just in case ...and New terminals soldered on last yr). Cam Sensor?? Ign switch? It doesn't feel like tranny based on tranny problems I've had on other vehicles, but... any readings you think I ought to look at with the trans? I mean, I suppose it could be a torque converter. But idk. I know just enough to be dangerous here, lol.
During the test drive below (after pulling coils/plugs and reinstalling), I took a long test drive. I was not able to reproduce the "chugs" or misses (I could 'feel) during that 50 min drive. But looking at the misfires below I see they occur at the same time. Note: There's a low RPM period where I needed to pull off the road to check & answer a couple emails..that's not a glitch. Anything jump out at you guys? Any thoughts? Has anyone experienced something like this before? What else should I look at? Really appreciate your thoughts. Thanks!
Been having a 'miss' where she bucks at times between 52-62 mph ...and pretty much ONLY during longer flat-road cruising periods, or even a bit worse if the road is a slight incline (when engine is under a higher load, before it wants to downshift). Usually at around 1,825 RPM. Please see misfire graphs below. Let me know if you have any ideas. Sometimes it never chugs ...all day or a couple days. Sometimes under the right conditions it may do it a fair amount and once it starts it tends to do it quite a bit (again, on flat cruising between the speeds listed above). But if I kick it down a gear it stops 'chugging'.
Note: I don't feel any 'misses' outside of the 52-62 window during, nor are there any misfires (by real-time scanner) during: Acceleration, deceleration, and very few at speeds outside the window I listed above. The vehicle has not set any misfire codes ..so its below the misfire threshold. HOWEVER, the total misfire counts in a 50 minute test you can see in the first chart below (upper Rt hand corner). Obviously Cyl #4 has something going on. #4 misfire condition was appx the same before and after I swapped coils (but didn't change plug orientation (which I will put a new one in it's place). Iridium plugs are about 4yrs old. I pulled the coils and plugs. Did not see anything visually. I ohmed them out ....will research my readings tomorrow. One coil ohm readings did seem way off, but oddly it is Cyl 5 below. Not a particularly high misfire cylinder. The plugs seemed fine by eye & ohm reading. As I mentioned, I replaced the plugs in the same orientation, but reversed the coil locations to see if the misfires would change to the new locations. They didn't. Compression is: #1=137psi, 2-5=150psi.
I replaced the MAF sensor a few days ago with a GM (OEM) sensor, as I noticed the Air Intake Temp was 'off' even after cleaning. I did buy a new plug for #4, and will install it to see if that changes anything. What I find interesting is that all cylinders pretty much spike at the same time. Although when they do, #4 has many more misfires ..but it seems to do it during the time they all do. Also I noticed for whatever reason the fuel signal periodically spikes?
What do you think? Possible idea which come to my mind are: Check Grounds, Check alternator output (battery is new BTW, recently charged up just in case ...and New terminals soldered on last yr). Cam Sensor?? Ign switch? It doesn't feel like tranny based on tranny problems I've had on other vehicles, but... any readings you think I ought to look at with the trans? I mean, I suppose it could be a torque converter. But idk. I know just enough to be dangerous here, lol.
During the test drive below (after pulling coils/plugs and reinstalling), I took a long test drive. I was not able to reproduce the "chugs" or misses (I could 'feel) during that 50 min drive. But looking at the misfires below I see they occur at the same time. Note: There's a low RPM period where I needed to pull off the road to check & answer a couple emails..that's not a glitch. Anything jump out at you guys? Any thoughts? Has anyone experienced something like this before? What else should I look at? Really appreciate your thoughts. Thanks!
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