I'm not sure what changed the code to go from the #1 cylinder misfire code to random misfire even though i fixed the problem for the # 1 cylinder. I found out that the fuel injector was bad for the #1 cylinder and replaced it. I replaced the sparkplugs and wires, checked the coil packs and they are good. I need to know what else I can check for or if i need to put it in the shop. Can you please help?
An intake vacuum leak can cause this as well as other issues, read about it below.
Check Engine Light On, P0300 Random Misfire Code
A random misfire means your engine is misfiring, but that the problem is not isolated to one or two cylinders. It is jumping around in a random way from one cylinder to another. A random misfire code usually means the air/fuel mixture is running lean. But the cause might be anything from a hard-to-find vacuum leak to dirty fuel injectors, low fuel pressure, a weak ignition coil, bad plug wires, or compression problems. Even a dirty MAF sensor can cause a lean code and/or misfire to occur. The engine may be stalling because it isn't getting enough throttle opening. The cause is often a problem in the idle air control system. The first thing to check is the intake vacuum with a vacuum gauge. On most vehicles a normal reading is 17 to 21 inches Hg. If the needle is lower, is jumping up and down or steadily dropping, you have a vacuum problem. Look for possible vacuum leaks by checking vacuum hose connections, the throttle body and manifold, and PVC valve and plumbing. An EGR valve that is leaking can also act like a vacuum leak and cause a random misfire. The next thing you should check is the fuel pressure with a gauge. If it is not within specifications (refer to a service manual for specifics because fuel pressure is critical for proper engine performance), the problem may be a weak fuel pump, low voltage to the pump (check the relay and wiring), or obstructions in the fuel line (like a plugged filter). A bad fuel pressure relay can also leak pressure and prevent an otherwise good fuel pump from delivering full pressure to the injectors. Dirty injectors can also restrict fuel delivery and cause a lean fuel condition. Many regular grades of gasoline do not contain adequate levels of detergent to keep the injectors clean. Frequent short trip driving accelerates the buildup of injector deposits. Cleaning the injectors with a good quality fuel tank additive (or having them professionally cleaned) can solve this problem. Look at short term fuel trim (STFT) and long term fuel trim (LTFT) with your AutoTap Express DIY. If the numbers are high, it tells you the engine is running lean
SOURCE: 1998 Cavalier No Spark in cylinders 1 & 4
ignition mod. grounds,pcm or timing belt could all be it but, I would have to look at timing first.
SOURCE: 2003 Chevy Venture misfiring
The injector is a good possibility, although you should check for spark in the wire first, as the electrical is the weakest link in the system. Put a spare plug in the end of the wire with the plug resting on metal, then have someone crank the van to see if you have spark that far, test and replace spark plug, (do not get shocked!) then look into a new injector or a good cleaning.
SOURCE: Has a 6.0 L with bad misfire under a load and is
Hi Brad,
I ran into the same problem your going thru,
swapped cylinder plug and wire ,and the scan kep telling me it was still seeing the problem on the same cylinder,
smoked it too,nothing made sense!
Until i took the whole fuel rail off carefully not to let the fuel run out all over the engine,Had a white rag folded up and handy,tilted the rail assembly and left the fuel run on the cloth,OMG! the rust that came out of there,
I pulled every injector out of the rail,cleaned the inside of the rail with air pressure and carb cleaner.
Its when I was checking the injectors that I found the culprit,the rust pieces had made it thru the injector but were trapped in the screen of the injector!
I hope this cures your.
SOURCE: Code P0300 misfired detected. I have cylinder 1
sound like bad ignition module.make sure where coil pack set in module contacts is clean and making good contact.also make sure plugs and wires is good.
93 views
Usually answered in minutes!
×