Cat C15 misfire

I had one with a misfire on cylinder 6. After about 23k thrown at it, it ended up being the plug to computer had broken pin, messing up connection to computer, showing the misfire, causing it to miss…
Maybe yours is snowball, ended up being a $500 plug on mine.. good luck

 

It's important to clarify that "backfire" is a term more commonly associated with gasoline engines. Diesel engines operate on a different principle, so the causes of similar-sounding events are different. However, diesel engines can experience issues that result in loud noises and exhaust expulsion, which might be mistaken for a backfire. Here's a breakdown of potential causes in a diesel semi-truck:
Common Issues Mistaken for Backfires in Diesel Engines:
* Fuel System Problems:
* Malfunctioning fuel injectors: If injectors are not delivering fuel at the correct pressure or timing, it can lead to incomplete combustion, resulting in loud noises and excessive smoke.
* Clogged fuel filters: Restricted fuel flow can disrupt the air-fuel ratio, causing misfires and irregular combustion.
* Insufficient fuel pressure: Similar to clogged filters, low fuel pressure can lead to poor combustion.
* Air Intake Issues:
* Dirty air filters: Restricted airflow can disrupt the air-fuel mixture, leading to incomplete combustion and excessive smoke.
* Faulty airflow sensors: Inaccurate readings from these sensors can cause the engine's computer to miscalculate the air-fuel ratio.
* Exhaust System Problems:
* Exhaust leaks: Leaks in the exhaust system can cause loud noises and the release of unburned fuel or combustion byproducts.
* excessive back pressure: a restriction in the exhaust system can cause gasses to be forced back into the engine, causing loud noises.
* Turbocharger Issues:
* Turbo lag and surges: Turbochargers can cause fluctuations in air pressure, which can lead to incomplete combustion and visible smoke, especially during acceleration.
* Turbo failure: A failing turbo can cause many issues, some of which can cause loud noises.
* Engine Problems:
* Valve problems: Improper valve timing or damaged valves can disrupt the combustion process.
* cylinder issues: if a cylinder is not firing correctly, it can cause unburnt fuel to be expelled into the exhaust system.
Key Differences from Gasoline Engine Backfires:
* Diesel engines rely on compression ignition, not spark plugs. Therefore, the classic "backfire" caused by ignition timing issues in gasoline engines is not typically a factor.
* The "loud noises" in diesel engines are more often related to incomplete combustion, fuel delivery problems, or exhaust system issues.
If a diesel semi-truck is experiencing loud noises and excessive smoke, it's crucial to have it inspected by a qualified diesel mechanic.

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This is produced by Google's Gemini (AI on Pixel phone). I recently had a couple of misfires and asked Google the question. Leaky injector? Exhaust valve timing intermittently off? I recently had an exhaust rocker roller going and replaced-along with the camshaft. And then had 2 misfires 8,000 miles later. Had everything checked out again: injector cutout, overhead, leaky CAC, fuel pressure. Couldn't reproduce on a dyno. Concluded it was an intermittent fuel pressure drop because of a FASS pump that's been cutting in and out intermittently due to a bad wire harness. I hope so because I'm getting ready to change it, and the fuel lines because they've been in there for well over 1 million miles. I believe that interior fuel line separation can cause fuel pressure to flutter.

 

Misfire and back fire are a long ways apart.

Misfire on 1 and 2 check your wire harness under the cover as well as all the way back to ECM. CAT is famous for securing the harness too tight. Years of vibration cause the copper strands to break without hurting the insulation. You can see and feel a slight indentation on wire in that spot

Other options can include a blown head gasket between cylinders. You need to narrow down is it mechanical or electrical causing the problem. Throwing parts at it gets expensive

 

Yeah, I learned that after I asked the question to Google Gemini.

 

Start rechecking your electrical you’ve missed something

 

You can rule out fuel pressure, air in fuel or partial plugged return line if your 100 percent positive your miss is isolated to 1&2. If not the put a restriction gauge on it between the water separator and the gear pump. Check your regulator valve in filter head. Put a sight glass before and after the lift pump. Also check the return line coming out of the back of head I’ve seen them get sorta plugged and cause a problem.


it would be odd to have a bad lobe on cam on 2 cylinders at the same time but possible. I’m sure you checked that…..

Only so many things will cause a miss and when you’ve checked them all well it means you’ve missed something start over. You can move injectors around to see if the miss moves which will rule out the possibility of 2 bad new injectors. Again not impossible but odds are very slim. I’d go for 1 of the 2 but not both. However I’d rule it out 100 percent at this point.

 

1 & 2 share a ground. I would be testing that engine harness wire with a headlight. 1 & 2 injector connectors aren't crossed also.

 

I do not know a lot about that but will share this. Have a friend that had a Acert that would have skipping - misfiring fits. I rode with him and a Pro Link. It did not read any faults while having fits. Then it would go away. He got caught out of town on 5 cylinders and at a dealer. I do not remember what they did for a $1000 but it ran great. He left and turned around after 2 blocks. Ended up being a problem with harness up around the balancer.