Chevy Misfire cylinder 3

P0303 CHEVROLET - Cylinder 3 Misfire Detected... Possible causes - Faulty spark plug 3 - Clogged or faulty fuel injector 3 - Faulty ignition coil 3 - Fuel injector 3 harness is open or shorted - Fuel injector 3 circuit poor electrical connection - Ignition coil 3 harness is open or shorted - Ignition coil 3 circuit poor electrical connection - Insufficient cylinder 3 compression - Incorrect fuel pressure - Intake air leak... The P0303 code means that the cylinder 3 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 3. If the problem persist more tests needs to be done to diagnose problem, like a compression test on the cylinders... Engine Cylinder 3 is Misfiring.. Possible symptoms - Engine Light ON (or Service Engine Soon Warning Light) - Lack/loss of power - Hard start - Engine hesitation

Yeah the code is 303 installed new plugs And wires and spider injectors fuel pressure is good I don't honk its possible but could the timing cause the two hard codes p0300 and p0303 she runs great very quiet no sign of miss a tiny I mean tiny hesitation at start I need to get a more detailed scan now that the light has come back on

No, timing does not cause a miss-fire. You actually have a random miss-fire by the looks of it. po300 is random, po303 is a miss in cylinder #3 now. Here are some things to check....P0300 CHEVROLET - Cylinder Misfire Detected Random Cylinders... Possible causes - Faulty spark plug (s) - Faulty ignition coil (s) - Clogged or faulty fuel injector (s) - Intake air leak - Fuel injectors harness is open or shorted - Fuel Injectors circuit poor electrical connection - Ignition coils harness is open or shorted - Ignition coils circuit poor electrical connection - Insufficient cylinders compression - Incorrect fuel pressure...........P0303 CHEVROLET - Cylinder 3 Misfire Detected.... Possible causes - Faulty spark plug 3 - Clogged or faulty fuel injector 3 - Faulty ignition coil 3 - Fuel injector 3 harness is open or shorted - Fuel injector 3 circuit poor electrical connection - Ignition coil 3 harness is open or shorted - Ignition coil 3 circuit poor electrical connection - Insufficient cylinder 3 compression - Incorrect fuel pressure - Intake air leak.............../ pretty much the same code.

Could engine wiring harness cause a misfire if it is cracked? i have a misfire on cylinder 4 and ive changed spark plugs, crankshaft sensor, camshaft sensor, coil pack, i think the problem is on the harness for the coil pack? what do yall think?

Eros...if you have wiring that has rubbed threw the insulation, that runs to the coil then yes, it could cause a miss fire. Peal the wiring harness insulation away at the bad spot around the wires and inspect the wiring. Look for bear wires and repair.

okay thank you, ill check the wiring after work, i read online that the coil pack wiring tends to break or after a while tear due to the heat from the engine but idk how true that is ill keep you updated if it fixes the problem!

Have you tryed the distributier had a 98 Yukon same problem tryed all the same fixes nothing work and my buddy told me to try to replace the distributor and it worked

Throwing this out there because no one helped me find mine. Pretty much same issue. Replaced more parts than you thanks to parts truck. However, it ended up being a broken valve spring. It wound into itself so it couldn't be heard when diagnosing, and still had compression, etc etc etc. Leak down, blah blah. Swapped coils, wires, plugs, injectors, etc etc etc. I eventually ran the truck HARD with seafoam injected until I broke "whatever it was", and could hear a very noticeable problem. Took valve cover off and it ended up being broken valve spring into 4 pieces. Dead miss on 6 was causing 5 to miss 20% of the time, but would only do so at certain rpm. Careful not to drop the valve down.

I installed brand new motor in my 96 chevy truck put new plugs and wires new distributor which is set at zero so I know its not that no intake leaks any where put new spider injectors in new crank sensor new cap and rotor still misfires on 4 6 8

Anybody figure this problem out I'm going thru same issues on 99 vortex misfire 2/3 changed spider cleaner dirty fuel tank cleaned fuel lines replaced filter ran good today to work 30 miles on way back home misfires started again any help would b greatly appreciated

The lifters can cause it to miss if you haven't checked that

I haven't seen anyone mention the ignition control module yet. These are known to fail. I just started having a misfire on cylinder 7 but only after driving for a while. I can pull over shut my truck off and clear the code and it doesn't come back for a little while. The ignition control module can cause a misfire. Hard start, or no start it just depends how the module is failing. It can also cause a misfire or stall after it heats up ie: after you have driven a while and then it misfires or stalls. Just throwing it out there for you guys it is real common on the 5.7 and 4.3 engines good luck.

1999 gmc yukon 5.7, Started getting radom misfires and severe loss of power under load as long as a year ago periodically. I replaced plugs with OEM and OEM WIRES new distributor and cap and rotor. New injectors two years ago and new fuel filter regularly HAD THREE fuel pumps as many are junk. This one is AC Delco OEM SPEC. Just had new Distributor installed and seemed good... until I tried to maintain 45 mph up a hill and it severely loss power I slowed to about 25 then it seemed like it is was clugging and then started to pick back up in power. DTC was misfire on Cyl #3 I am at a loss. Thining of ignition module as that isn't that expensive. Any other thoughts? Truck as 293000 miles and I love it! never did compression test yet as the random misfires baffled me.

I have Chevy Silverado Classic 1500 4.8 I have a miss fire on cylinder 3 my check engine light keeps coming off and on I had the spark plugs and wires change about year ago also there’s no air leaks.

I have a 99 tahoe 5.7 mine started misfiring. I replaced plugs wires cap rotor distributor then had it towedto shop for timing. After it was timed light comes back on. P0300 multiple cylinder misfire then 301 303 306. Im asking myself how much more you going to throw in this? So i went and bought ignition control module. Fixed my misfire promblem.

No one has mentioned the Mass Air Flow sensor. It can cause random cylinder misfires. Can also cause vaccume loss to engine. Can cause faulty fuel pump type systems such as lean fuel conditions. They can be bad even if they are reading proper voltage. Best way to check is to test voltage and fuel percentage when its hooked up vs when its unhooked. These procedures can be googled. They can also cause no start conditions due to improper fuel/air mixture.

I have a 96 5.7 it's crazy but I love this truck and not a mechanic only by YouTube cause I don't have the money tree but can seriously use some help I replaced fuel filter/pump camshaft sensor crankshaft sensor plugs and wires serpitine belt intake air temp sensor and took mass air flow sensor out and cleaned up and soaked it and still having intake air temp sensor come on and to the plug on sensor it's getting the right voltage 4.9/5.0 and it's still throwing a code for that and then after i replaced camshaft sensor it was throwing code for being out of correlation and I looked at YouTube and tried to fix it cause I thought I had it off in distributor and put it at top dead center and took rotor off and loomed at it and it wansnt really toward front #1 plug more towards the center of hood but anyways I tried that and drove it for bout 10 mins and that code went away somehow and now it still saying intake air temp sensor p0113 and p0303 which is cylinder 3 misfire and truck cranks right up just really no power driving and yo me sounds like cat is stuffed up but I don't have one so any advice really would help so the start of this search was because of truck driving like that sluggish in throttle and no power and sounding stuffed so after all my fixes still didn't affect the driving of truck so thsnks

Same problem with my 03 GMC Sierra 4.3... replacement of ignition module will help for awhile but all research I've done tells me module overheating and when cool truck runs fine for a few kms...I have gotten a few months out of a used module for parts Yard for $12.00

I have a 99 Tahoe but it doesn’t have distributor or rotor it has a coil pack

If loosing power then check compression! Mine turned out to have some bad valves on passenger side. Had that fixed. Now starting to have a little miss fire not sure which cylinder

Do a back press test on the catalytic converters, one on each bank. A clogged cat will give random missfire

So mine is misfiring cylinder 3 I’ve had the heads redone new spark plugs and wires next is the distributor

everyone, please make sure you check the vacuum, it should be 14.7 hg, and steady at idle. If its low or the needle is fluctuating, the car is not breathing properly, which indicates bad catalysts or some kind of air restriction.

Lower intake manifold gaskets! happened to me caused miss and or distributor also worn out piston rings too can cause miss n smoke at start of engine

The spider fuel injector harness on top unplug it and plug it back in multiple times. Fixed this same problem on two different trucks. Contacts are bad. Hope this helps. John.

Check the pins where the injectors plug in. I had the pins on the number 8 injectors were bent and not making contact with the plug

Need help!!!!! I have a 1996 Chevy c250 I did Spider injectors cap rotor plugs wires two new cats and still have a miss fire I can’t figure it out when running the one cat gets cherry red from geting to much fuel it started out as a Multi cylinder misfire then to Cylinder two misfire

Here's a run down on my experience with vortec engines. Had a truck come in with multiple cylinder misfires. Customer brought me plugs and wires and cap/rotor. Ended up replacing the cam sensor in the distributor to fix this truck..... Another truck came in with multiple cylinder misfires....they left it up to me to diagnose. Ran a compression check and all cylinders were around 135psi....what I found were some lean running cylinders via white plugs not similar to the nice brown tint to proper fueling. I proceeded to check plug gap and they were all gaped similar(.060). I run (0.40) on vortecs that in my experience works better/easier starting. The problem was a wore out spider injection system. I replaced the spider and got a cylinder 8 misfire instantly after starting it up....what happened was the fuel pressure regulator clip got pushed down while installing the intake causing it not to seal and dumping fuel straight down into that cylinder. Corrected that issue by pulling the intake back off and repositioning the clip. Another truck I had a bad fuel psi regulator straight out of the box! Same signs as previous truck. Replaced the regulator/fixed. Another spider replacement the wires got twisted around the fuel lines binding them up against the metal bracket that holds the spider head in place and the wires grounded out to the clip/engine causing multiple cyl misfires. Another problem on another spider i did was the pins to the connector. While putting the injector harness back on one of the pins got pushed down and wasnt making connection. Pulled it back up with pliers and ran a pick into the harness at the opening that was boogered up. Fixed. Ive seen a bank running lean die to a stopped up cat making it think it was running rich! Unhooked the exhaust couples to verify performance be for removing entirely and running g an inspection camera in it to find it clogged up.

same issue..... New distributor cap. New Copper Spark plugs New Fuel filter same issue continued Changed spark plug wires......Solved!

2001 Chevy Express 3500 with a 5.7L , New Cap , Rotor , Plugs and wires ., Still gives me a #3 Miss fire . What should I check now ?

99 suburban 5.7L Same Issue... Anyone have a Fix? This week I have replaced the cap and rotor 3 times, Fuel Filter and Pump, Replaced MAF sensor as it seem to gain power back but then fell on its face after a couple hours, New ECM, New Air Filter, Timing set to 0 Degrees, New Plugs, New Wires, New Cats, 4 new 02 Sensors, I have a check engine light on and its referring to 02 sensors air fuel mixture. This is a new Motor from ATK and has about 11000 miles on it. Cap and Rotor keep carboning up on the points which I believe is due to the crank cam correlation but i am at 0. Not sure where to go and most shops dont have a clue either

Check all spark plug wires for any damage remember spark plug wires pack a lot of voltage it doesn’t take much damage or cracking for plug wires to lose voltage.

Temperature coolant sensor

Well for all the misfire on cylinder 3 I change a lot of parts..came to fine out it was the wire plug they where brand new that is why I rule them out.. I hope this helps someone..