Followup to this thread: the issue returned. And it had followed the coil, which I had put in Cylinder 4 this time, and made sure the connector was seated. So it's a coil with an intermittent problem. It DOES happen.
Persistent misfire under load only
- Thread starter greiswig
- Start date
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Jimmy Brooks
Full Access Member
Hey all,
Getting a lot of similar symptoms with a D5 which has the SCV6. The misfire only happens under load and is mostly noticeable when the car is cold (oil is below 180) when first starting to drive. The misfire only happens around 2500-4500 RPM when under load in any gear from 4th to 6th gear. You can feel it in the form of jerking which gets faster but less present as rpms rise. Each misfire j€rk (it will sensor the normal spelling) you feel you can see it in the rpms tack, the tack will move down about 50-100 rpm each time. I got a code for random misfire and then cylinder 3 misfire a while back but I cleared it when I got an oxygen sensor code and replaced the sensor. The misfire is still there but I haven’t been able to get a code to come back. I replaced the injector spark plug and coil on what the scv6 diagram labels as cylinder 3. It is still there, I am currently in the process of doing the same thing to cylinder 2 (would be cylinder 3 on the V8). But I am not confident that this will fix it.
Would love to hear some thoughts and share more information if anyone could make sense of this. Let me know if anyone has any ideas, I’d like to avoid spending thousands on diagnosis and fixes at an indi shop.
Getting a lot of similar symptoms with a D5 which has the SCV6. The misfire only happens under load and is mostly noticeable when the car is cold (oil is below 180) when first starting to drive. The misfire only happens around 2500-4500 RPM when under load in any gear from 4th to 6th gear. You can feel it in the form of jerking which gets faster but less present as rpms rise. Each misfire j€rk (it will sensor the normal spelling) you feel you can see it in the rpms tack, the tack will move down about 50-100 rpm each time. I got a code for random misfire and then cylinder 3 misfire a while back but I cleared it when I got an oxygen sensor code and replaced the sensor. The misfire is still there but I haven’t been able to get a code to come back. I replaced the injector spark plug and coil on what the scv6 diagram labels as cylinder 3. It is still there, I am currently in the process of doing the same thing to cylinder 2 (would be cylinder 3 on the V8). But I am not confident that this will fix it.
Would love to hear some thoughts and share more information if anyone could make sense of this. Let me know if anyone has any ideas, I’d like to avoid spending thousands on diagnosis and fixes at an indi shop.
powershift
Full Access Member
Are you using the GAP? I've read that it can give the wrong cylinder number.
Jimmy Brooks
Full Access Member
I know, which is why I did coils plugs and injectirs on cylinder 3 on the V8 pattern and the V6 pattern no difference.
jlglr4
Full Access Member
Have you looked at fuel rail pressure or fuel trims? Under load only makes fuel delivery come to mind. Might check tsbs on that car as well. not sure what components might have changed in the new platform, and whether they might have had new issues pop up.
Jimmy Brooks
Full Access Member
I would’ve provided this data already but unfortunately the G3 gap tool shows limited live values on the D5. I’m going to have ti talk to the Gap team about upgrading, I’d really like to get the discounted trade in price for the G4 tool. I believe the discounted price is around $170 while the undiscounted price is $388 which is steep. Plus you need to have purchased the G3 tool from 2022-2024 and unfortunately I purchased mine in 2020. I guess it’s still worth an ask.
I agree with the fuel delivery aspect, praying that it isn’t the HPFP.
Jimmy Brooks
Full Access Member
Update: I am a huge *****. I’ve been doing research on the issue trying to make sense out of everything before pulling the trigger to upgrade my IIDtool. While doing research I had an idea to check if I had any lean/ricg codes stored in the PCM when I took a screenshot of the misfire code last year. Come to find out that the whole entire time the issue was on cylinder number 4… so I’ve been doing work on the wrong cylinder this entire time… **** me!!!!
Anyway I plan on attacking cylinder 4 this Thursday or Friday and replacing the plug, coil, and injector since I have working spare parts for each of them. Hopefully I report back with good news. If not, I might have to bite the bullet on a $388 IID Tool swap.
Anyway I plan on attacking cylinder 4 this Thursday or Friday and replacing the plug, coil, and injector since I have working spare parts for each of them. Hopefully I report back with good news. If not, I might have to bite the bullet on a $388 IID Tool swap.
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Jimmy Brooks
Full Access Member
Update: no difference. I replaced plugs coils and injectors, nothing.
Side note: I noticed that if I put the car in park and put my foot on the throttle in a fixed position rather than the rpms going to a certain speed and remaining there they will actually fluctuate about 300-500 rpms. When I do this in my LR4 they stay consistent. I’ll post a YouTube video to show this in the afternoon. I unplugged both MAF sensors and the car kept doing this.
Side note: I noticed that if I put the car in park and put my foot on the throttle in a fixed position rather than the rpms going to a certain speed and remaining there they will actually fluctuate about 300-500 rpms. When I do this in my LR4 they stay consistent. I’ll post a YouTube video to show this in the afternoon. I unplugged both MAF sensors and the car kept doing this.
Jimmy Brooks
Full Access Member
SCV6
Hey all,
Just have some more updates:
So I was snooping around last night and found that the PCV system had a leak. The pipe that comes off of the intake duct and goes into the PCV system for bank 2 was cracked where the male side of the pipe fused to the intake duct. I sealed it shut with JB weld and let it cure for 15 hours. After this I put everything back together and gave it a test drive. To my surprise this fix exaggerated the issue a ton. I will persistently buck from 2500-5000 rpms now. Oddly enough, right at 5k rpm the engine goes completely smooth and runs normal.
My question is why would fixing a PCV leak make this issue more prominent?
I would really appreciate any thoughts or inputs you guys might have. Here is a like value screenshot, you can see the jumping of the rpms as I accelerate, when it hits 5k I shifted into another gear which is why you see a big rpm drop.
Still, the engine is reluctant to throw any code.
Hey all,
Just have some more updates:
So I was snooping around last night and found that the PCV system had a leak. The pipe that comes off of the intake duct and goes into the PCV system for bank 2 was cracked where the male side of the pipe fused to the intake duct. I sealed it shut with JB weld and let it cure for 15 hours. After this I put everything back together and gave it a test drive. To my surprise this fix exaggerated the issue a ton. I will persistently buck from 2500-5000 rpms now. Oddly enough, right at 5k rpm the engine goes completely smooth and runs normal.
My question is why would fixing a PCV leak make this issue more prominent?
I would really appreciate any thoughts or inputs you guys might have. Here is a like value screenshot, you can see the jumping of the rpms as I accelerate, when it hits 5k I shifted into another gear which is why you see a big rpm drop.
Still, the engine is reluctant to throw any code.
Attachments
Sorry for your troubles. Why does your diagnostic tool seem to think it’s looking at a diesel engine? I’m not sure how trustworthy are the readings you’re getting.
