Slight low ticking noise and check engine light came on

Tiny
ZANEAC22
  • MEMBER
  • 2009 JEEP GRAND CHEROKEE
  • 5.7L
  • V8
  • TURBO
  • AUTOMATIC
  • 100,000 MILES
Three weeks ago my vehicle started to have A slight low ticking noise. Then a week later a solid check engine light came on. I checked codes and it showed cylinder three misfire code. I was told to put high octane fuel, in it with octane booster and I did. My light started to blink and since then blinks only for a minute and not every time when started and if reved. I checked my spark plugs for damage in cylinder three not apparent damage but want to change then to make sure and switched cylinder five coil with three to make sure was not coil and my coil is fine. So I was told change spark plugs can I get some advice to make sure I am doing what I need to do? I do not want it to be a major problem and make it worse it is running very rough and I am afraid of breaking down.
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Monday, December 26th, 2016 AT 11:42 AM

2 Replies

Tiny
HMAC300
  • EXPERT
It is probably still misfiring as it is running rough, you can check fuel pressure with a gauge and look for a vacuum leak. However, these are very hard to find and cheapest option is to let a mechanic do it so he can check sensors/injectors or basic engine problems because it can be any of those.
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Monday, December 26th, 2016 AT 11:57 AM
Tiny
CARADIODOC
  • EXPERT
The last thing you want to do to solve a misfire is use higher-octane gasoline. The higher octane makes the fuel harder to ignite so it is less likely to have pre-ignition or spark knock. When you have a spark-related misfire, you do not want to make the fuel even harder to ignite. Octane booster is even worse. The only thing that solves is it increases the octane rating for those engines that require it, and you cannot find that gas at any gas station.

Many people still think higher-octane gas develops more power, so they use it, thinking that is what they will get. In fact, the higher octane allows engine designers to build an engine that produces more power, through a higher compression ratio, but the purpose of the higher octane is to cancel the negative byproduct of that higher compression, which is pre-ignition. You always want to use the lowest octane gas possible that still does not cause spark knock.

Start by running out the gas you have now then put the right stuff in the tank. Be aware the flashing "check engine light" means you are supposed to stop the engine right away. Too much unburned fuel is going into the exhaust system where it will burn in the catalytic converter and overheat it. That becomes a very expensive repair. Replace the spark plugs first, and erase the misfire fault code. If the problem comes back, do a search for service bulletins related to this engine. A former student told me about a problem with the cylinder head, but I cannot remember the cause or which engine it applied to.
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Monday, December 26th, 2016 AT 12:16 PM

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