Perhaps someone can help advise me on this. Engine light is lit. Sometimes the code is cyl 1 or 4 misfire. When idling, the engine light will blink sometimes. It’s all random. Seems to happen more when tank is half or less. Thought it was the injectors, but now I’m starting to think it might be the fuel pump. Does the OBD record fuel pressure? If not, how can I check it? I need to check when tank is full and when half or below. Any ideas would be most helpful! Thanks y’all!
Engine misfires
- Thread starter Radioflyer1105
- Start date
What model year Jeep and which engine do you have? Your Profile is devoid of any information. The OBD does not record actual fuel pressure. Misfires can also be caused by a bad upstream O2 sensor which is responsible for setting the air/fuel mixture. Like spark plugs, O2 sensors do eventually go bad. If you decide to change them make sure to ONLY use NTK or NGK branded O2 sensors, don't use Bosch! 
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It could very well be the coil packs.
More information is needed though as Jerry pointed out.
For instance, what engine, what year, and what specific codes is it throwing?
More information is needed though as Jerry pointed out.
For instance, what engine, what year, and what specific codes is it throwing?
Gentlemen, thank you for the info. Here are the answers to your questions. I have a 2006 Wrangler Rubicon with the straight 6 cylinder engine. I think it’s the 4.0L engine. Manual transmission, and Ive got 170k miles on it. As for the O2 sensors, I believe the upstream is before the pre-cats. I replaced the sensors a few years ago. I replaced the cats a few months ago and transferred the O2 sensors over, since I hadn’t had any issue with them. Ive been thinking about replacing the one just past the pre-cats because when the pre-cats blew out, they dented the sensor. Ive been troubleshooting this issue pretty soon after replacing the cats, and thought it was just dirty injectors or something in the lines. Ive put quite a bit of Lucas injector cleaner thru the system. The coil pack was replaced right before the cats were replaced, and I used the warranty to replace it again because the cylinder misfire codes continued after replacement. Like I said initially, I was thinking it was bad injectors, but the engine tends to run fine from a full tank to about a half tank, although that isn’t always the case, but pretty consistent. That’s what got me thinking about the fuel pump because the volume of gas aids it pressure at the pump inlet when the tank is full, but reduces the effect as the fuel level decreases. I hope this info helps
Yes I am, but when the engine runs good, the computer will clear the code. It’s always either cylinder 1 or 4 misfire that comes up. Also, when the engine is running rough, the engine light will blink. From what I have read, this means the cats are being damaged, so I’m assuming there is either too much oxygen or not enough that they are measuring.
Gentlemen,
Thought I would post an update. I replaced the fuel pump and pressure regulator. While I had the tank dropped, I sanded down the tabs on the overflow preventer to provide for smooth movement without sticking, which it was. Engine ran great at start up. Filled the tank, and I’m happy to report, the fuel spillage I have been dealing with for years is gone, thanks to sanding down those tabs! I just turned on the gas handle and let it run. It stopped like it was supposed to! However, the missing of the engine came back when the tank got towards empty. I will be replacing the upstream O2 sensors this weekend, and the downstream ones after I drive the Jeep for a tank or two, to see if the upstreams fix the problem. And yes, I got the NTK sensors! LOL! If I still have issues, I will check the coil pack (again), and replace it (again) if needed. After that, it’s moving to replacing the injectors, I suppose. However, I am always up for suggestions!
Thought I would post an update. I replaced the fuel pump and pressure regulator. While I had the tank dropped, I sanded down the tabs on the overflow preventer to provide for smooth movement without sticking, which it was. Engine ran great at start up. Filled the tank, and I’m happy to report, the fuel spillage I have been dealing with for years is gone, thanks to sanding down those tabs! I just turned on the gas handle and let it run. It stopped like it was supposed to! However, the missing of the engine came back when the tank got towards empty. I will be replacing the upstream O2 sensors this weekend, and the downstream ones after I drive the Jeep for a tank or two, to see if the upstreams fix the problem. And yes, I got the NTK sensors! LOL! If I still have issues, I will check the coil pack (again), and replace it (again) if needed. After that, it’s moving to replacing the injectors, I suppose. However, I am always up for suggestions!
3lt4v0
New Member
Aquaman
New Member
I gave up trying to find my Cyl1 misfire and took it to a shop. They diagnosed it and said the head gasket was leaking antifreeze into the chamber. I'm paying them $1600 to change the Oil Pan Gasket, Intake manifold gasket(machining them too),Valve cover gasket, and headgasket(also machining the head. What y'all think?