# Carbon build up on Valves? Prevention? Treatment? How often to change oil? **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** integra, acura\ **Created:** [March 22, 2021, 8:04pm UTC](https://community.cartalk.com/t/carbon-build-up-on-valves-prevention-treatment-how-often-to-change-oil/175779 "2021-03-22T20:04:19Z")\ **Posts on this page:** 1\ **Showing post:** 65
**Author:** ![sciconf](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@sciconf](https://community.cartalk.com/u/sciconf)\ **Post date:** [March 24, 2021, 7:50pm UTC](https://community.cartalk.com/t/carbon-build-up-on-valves-prevention-treatment-how-often-to-change-oil/175779/65 "2021-03-24T19:50:53Z")
> [@shanonia](#): > > This is the first mention of misfire. If you want help with this, give us more info about the circumstances and symptoms of misfire. > > Some old Hondas/Acuras with distributors develop some play in the shaft. There is also an electromagnetic pickup in there - like a crankshaft position sensor. Those can interrupt the ignition, especially when hot, when they start to fail. How’s the cap and rotor, if present? Current state: M/c fixed the vacuum leak. Lean condition became Rich condition that he is investigating now. I tried to suggest that the computer needs to re-learn! He also did not test fuel pressure. Fuel Trim - Originally: 1500 rpm 2500 rpm LTFT 6.2 6.2 STFT 6.2 8.6 After I disconnected the battery and let all the Capacitors discharge: LTFT - 4.6 STFT - 7.8 - 12.5 Originally: - idle random misfire P0300, P0304 and occasionally P0303 - Changed spark/ front O2 sensor (OEM) - Spark is platinum a level up from OEM - Changed cap/rotor, spark wires with aftermarket parts - still misfire - Swapped the Dizzy coil but still misfires - Engine compartment is dry except Dizzy neeeded a new O ring - took care - Compression was good 175 to 190 (renage 135 to 199) - M/c did the leak down test and no issues - I added S1 fuel injector cleaner and the car started running fine (for a day!) but then misfiring closer to 2400rpm on road and not on P gear. Misfires on all Cylinders. Basically it misfires at idle and stops once warmed up. But on the road, it misfired around 2400rpm. - Owned the car for over 15yrs with little issues.Last yr IACV had to be cleaned. Carbon build up stopped its functions temp - after cleaning it started running like a new car. Throttle body is clean. - Use Mobil 1 5W30 every 5k. - valves adjusted 22k miles ago - air filter has 8k - Spark plugs did not show any abnormality - Batt and Alternator tested fine - cold start gives gas smell through exhaust even before the misfire - only known issue is the car would need jump start if you don’t drive for 2 weeks Related thread: [https://community.cartalk.com/t/are-the-cap-rotor-still-good/175532](https://community.cartalk.com/t/are-the-cap-rotor-still-good/175532) Update: I did edit here and there and added new info. --- _[View the full topic](https://community.cartalk.com/t/carbon-build-up-on-valves-prevention-treatment-how-often-to-change-oil/175779)._