11 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHinteresting misfire?
Leading reported evidence
Replace every june and december
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
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1
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Leading evidence: 'Replace every june and december' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust mechanically)' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
Plugs and coils were changed in December for maintenance only.
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Suggestion
They function like most hydraulic lifters in that they take up the clearance hydraulically, ( to avoid having to adjust mechanically) .
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Suggestion
Not particularly difficult, but it's a lot of work - and who knows what you'll want to fix/replace "while you're in there"...
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Suggestion · Original poster
Car is extremely well maintained and see's oil changes every 6 months no matter what.
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11 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261027T020439Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I have owned my 04 C4s for 15 Months. I have not had any issues with this car other than typical maintenance. During all types of driving the car operates perfect. No issues at all. No abnormal noises. The car gets driven only on the weekends and see's about 6,000 miles a year. I have noticed for quite some time now that if i blip/rev the throttle at idle, it will misfire once it returns to idle for about 5 seconds. Scan data shows this is happening on cylinder 1. So again to explain. If i drive ANY way i want, cruising, aggressive, autocross, long or short trips, it will be perfect. I will never have a misfire. But if i come to a stop and blip/rev the throttle somewhat aggressively it will misfire after returning to idle for 5 seconds. This can be replicated very easily. However i must be somewhat aggressive to make it happen. If i slowly increase the rpm's it will not happen. Plugs and coils were changed in December for maintenance only. I am pretty sure the problem was there prior to the plugs being changed. Car is extremely well maintained and see's oil changes every 6 months no matter what. 68,000 miles on the clock. No check engine light and no history codes. All scan data looks good that i see. Cam deviations are 1 degree and 3 degrees. MAF voltage looks correct. Fuel trims are perfect at all times. O2 sensors are switching perfect. Below is a video of the scan data proving it is on cylinder 1.
video
Looks like the an intake lifter sticking at high lift on cylinder 1.. This is a classic problem... It takes a certain throttle opening and RPM for the "high lift" portion of the Vario-Cam Plus to activate... once it does and you let off for the engine idle, one of the intake lifters on cylinder one is sticking for a few seconds.The long duration/high lift does not produce as much power at that RPM..
How old is the oil, sometimes new oil will stop it, if not replacing the lifters is the only cure. Since you have verified which cylinder you could just replace the two intake lifters on cylinder 1. Its a pain in the *** when it is so intermittent that you can't "catch it in the act" and have to replace ALL the lifters. (expensive too).
Oil is changed every june and december with DT40. So maybe 3 months old. My problem is i am all about fixing what isnt broke yet. So if i know me, and i think i do, i would wind up doing so much "while your in there" crap i mine as well rebuild the damn thing. If i go that far i know i would want to change the guides.
When they fail completely do they just collapse and keep the valve closed or is there a risk of major damage? I may just leave it alone until it actually occurrs under normal driving conditions.
These lifters have two separate functions.
1. They function like most hydraulic lifters in that they take up the clearance hydraulically, ( to avoid having to adjust mechanically) . this is done in the center chamber, and where they can collapse, but will do no harm, just clack and be noisey.
2. The pin slides over to lock the center to the outer. This is done when the" Plus" solenoid energizes and sends oil pressure to move the pin. Locking the center to the outer allows the lifter to follow the high lift/long duration profile of the cam.Neither position will be harmfull, just not ideal for power/efficiency/smoothness..
Yours has a sticking pin !!!
Thanks for the help and bad news lol. Since all is well during every other driving condition i think i will leave well enough alone untill it gets worse. Been a tech for over 20 years so i'm not worried about the repair. I will admit that i have never gone into a porsche motor so it would be foreign territory for me. At the shop i work at we focus on domestics and foreign, just not typically german. This jobs looks like a huge pain in the butt so i will happily delay it till i have to get it done.
The job of replacing the lifters themselves is a piece of cake (especially for someone who does it for a living). Getting the motor out, not so much! Not particularly difficult, but it's a lot of work - and who knows what you'll want to fix/replace "while you're in there"... basically, it's a can of worms...
Time and laziness is more of my issue. Working on cars all day long makes it so i don't want to work on my own. Not to mention i don't have the cam locking tools for this car. the "while you're in there" issue is going to kill me. Already thinking about the AOS, starter, y cable, alternator, chain guides........... I hate my brain
