2004 silverado Z71 flashing check engine light

good guess, the evap system is throwin up the red flag, probably your gas cap is missing, not tight, or you're overfilled the tank chokin' off the evap canister (guilty of this myself) it will recover with use, the light will go off if you've corrected with the proper fuel cap and not over-filling the gas tank....also you may need an oxygen sensor...all these and more can be found out if you go on by your parts store NAPA, O'reilly, kragen will do this for free, write down the information and relay it to the gurus here, we will tell you exactly how to correct the situation if none of these 'pinata' answers work!~

Sorry. Forgot to also say that I've had the truck scanned many times the 1 time it said multiple misfire so I changed the plugs and wires. 2 time I got him to clear all the old codes and drive it for the day and got it scanned again. Said that the #8 cylinder was the issue of the misfire. So swapped the coil with another on the truck to see if that was the problem. But then the 3rd time it says that all cylinders but #4&6 have misfired.

Have you changed the plugs? Air filter?

Yes. I've changed the plugs and the wires. Haven't checked the air filter. Would that make the truck misfire at any time? I'll still check it due to having no idea what the problem is.

change your bad coil pack and call it skippy!

I'm not sure if its the coil pack? It had only said that the one cylinder was bad once and it's back to 1,2,3,5,7&8 misfiring. And call it skippy?

well these are usually in pairs, that's why I assumed you had coil packs. by 2004 practically no one was using a distributor. but used pairs of coil packs...there are ways of testing these, take an ohm reading and compare that to the ones that work, and you'll know what to replace- skippy, yes like the peanut butter. seemed like a smooth exit~

Been doing my research and only finding that the fuel filter on this generation of silverado is the same as the fuel sending unit. and it has been replace within the last 4-5 months.

I checked the chiltons book and it says 05 and up have only filters on the sending units and they are not replaceable. Since yours is an 04 its possible your in the same boat too. My 03 has an inline filter in the frame in the area below the drivers seat. According to the chilton's book yours should too. Wouldn't be the first time the book was wrong though. I would check your fuel pressure it sounds like your 4 and 6 cylinders are not mis firing and those are the closest to where the fuel line enters the fuel rails. There's a possibility that there is not enough pressure getting there and or not enough fuel coming through the lines

My 05 silverado is idling rough. CEL started flashing while parked. Soon after CED went off and truck was idling fine. Just happened an hour. Any thoughts.

Read and CLEAR THE CODES... with a small 15 dollar handheld OBD-II scanner~

that thing will come on if you did not fill the tank properly....stoppin' at the first click (which NO ONE can seem to do)~ the charcoal canister will get stifled but should recover~

Judge_roy, already on top of it. Ordered the code reader ten minutes ago. Are any steps I need to take in the mean time?

BTW: I did NOT stop after the first click. Is it pretty likely this is my issue? This is my first Silverado. Never had to worry about that in my Lexus ES 300.

the OBD-II port is within three feet of the ignition switch...this is a dandy item because you can read EVERYONE's trouble codes now too~

yes....guessing the CEL came on after you gassed up...then yes...the heated 02 sensors DO need full power to operate the "HEATED" part correctly for correct readings....with any luck you haven't got an heated 02, but just a plain 02...which is very fussy, touchy technology~ the wire is more important than the platinum part~

What's steps should I take if it is a over fill issue?

,,,hey....lookin' back this is the first damn entry in this dialogue~

yes....the "black tape" solution will have to do until you run the tank down to say 3/4 fulll should go off and have sufficient vacuum to correct itself~ CLEAR the CODES with that 15 dollar scanner and it's off to the races~

I sprung for the $60.00 scanner. It did smell a little rich during this episode. Reading now about O2 sensors. I just freaking bought this truck (used). I love it, but really want it to last. Trying to stay on top of maintenance.

it's about vacuum at this point...you can keep your fingers crossed and hope that fuel ain't gettin into the vacuum supply...this might cause problems with the computer deciding what to do with it's air/fuel mixture~ .....as the substitution of fuel instead of air might cause it to cough a bit...maybe not...quite certain this HAS come up before and the Engineers think of everything....don't they~?

most troublesome is the "purge valve" which will NOT let you put fuel in...well, I oughta!! seen people having to fill with a funnel...all because the valve got damaged and will not allow liquid or gasses in....very helpful~

if you can sense that the timing chain and gears sound normal (not a can of folger's) you've got a real sweet ride....frankly am jealous...my wife makes me keep "bessie" the 93 toyota with 250,000 hard miles on it~

I traded up for my Lexus (Toyota) with 225,000 long and hard miles. It's was actually my wife's idea. Can you believe that. I was aiming for 300k. Oh well. Hope to put 300k on the bow tie now.

....well you cannot haul that old water heater to the dump with a Lexus...gotta keep the Toyota for "dump runs"....unsavory as that sounds...the MINI cooper is not happy with this NO pavement, but boulders that will smash up the undercarriage.....so mostly do not drive the mini which has only 36,000 miles on it~ in your case the BOWTIE (as you put it)~

ON THESE trucks it can also sometimes be a knock sensor or crank sensor that can cause a misfire or low fuel pressure or even intake gasket leaking. to check knock sensor shouold always throw a code. but on the crank not always needs to be put on a scanner and watch the info from the motor it can not send a single which would show up and cause a misfire but not always a crank shaft code. just possiabilitys

I also have a random misfire on my 04 silverado 5.3 with 135,000 miles. Dealership took motor apart ($1100) to no avail. They said it's my #2 and #7 cylinders. The number 2 is being caused by number 7 misfire. Parts I've replaced: Bank 1 sensor 1 (drivers side upstream o2) MAP sensor Plugs and wires Crank position sensor Throttle body which includes IACV and TCS Compression and fuel pressure checked by GM dealership.... Need serious help. My truck will not pass inspection with engine light on.

did u ever figure it out wgjones73? going thru the same thing with my 03 z71. missing on 6 outta 8 and throwing code for crank sensor and a bunch of evaps. runs rough as u step on gas tho, idles ok for the most part!

Read the codes to determine if sensor ! Go from cheapest to most difficult solution! Oreilly Autozone will let you use a OBD SCANNER for free!

If on my 04 Silverado the injector is clogged will it still make a clicking noise

It could jayZ71 mine did.

Now my oil has gas smell to it cause its missing I gotta see witch coil pack has went out

If my catalytic converter is stopped up wouldn't the engine run hotter than usual

Yes catalytic would kill the engine! Have you cleaned inspected sensors crankshaft etc? But evacuate the vapor system if gas entered into it! These are closed systems designed to keep emissions low!!

I got my codes read and the first thing that popes up is running Lean then multiple miss fire do u think its my fuel pump it doesn't miss at high rpm also no fuel filter

No filter yikes! If any contiminants get into to fuel injector it is going to get clogged and cause it to run sporadic! Yes if fuel pump is old replace it! But get a filter on it!!

i hope this is still somewhat active. i just got a used 96 chevy silverado 1500. it knocks pretty loud when idling and knocks when driving. when im driving it doesnt want to shift out of 1st gear unless i let off the gas at about 25-30mph otherwise rpm's just keep rising. i took it to get the codes read because my check engine light is on and flashes, he said o2 sensor bank 1 sensor 1 and bank 1 sensor 3, its missing, running rich, and something about a cylinder. can ANYONE help me?

I bought a 2003 silverado went to Texas to get it he said it was missing and cel was flashing I put fuel pump filters all the major sensors cleaned fuel rail injectors intake gasket was about to leave it there and already paid for it my dad told me to drill a couple holes in the driver side converter and beat it with a hammer and it runs great

If I ever have that problem again I'm drilling holes first it's free

Hey yall my 2004 Silverado had a misfire in the 6th cylinder and I replaced both 02 sensors on the passenger side and It ran fine then I started my truck soon after I fixed it and it would idle fine for about 25 seconds then start to misfire again then after about a minute and a half of misfiring it would stop and then it would idle justfine. It only misfires on startup and I need some help!!!

Craig if your truck only misfires on start up and it has a fuel pressure regulator that is controlled by a vacuum hose on the driverside of the engine it could be leaking into the #4 cylinder after sitting. If the regulator leaks profusely you could have a misfire most of the time. especially during idle.

my 2000 silverado 4wd 5.3, cel is on. In the mornings it flashes and seems to have power loss, poor acceleration. After work cel just stays on, no flashing runs fine. any ideas?

If when cold it misfires and runs poorly, the most likely cause could be leaking intake gaskets. They would be leaking vacuum. When the engine warms up the seals swell and the misfires go away. One way to test for this is to do the following. Have a spray bottle full of water read on a cold start up. Once the engine is running spray the water at the intake near the cylinder head over the valve covers. Do Not soak the intake! You could cause other issues. If the engine runs worse and you sometimes hear a sucking noise, then the intake gaskets should be removed. I hope this helps.

On my last post I stated that the intake gaskets should be removed. actually they need to be "replaced".

well it actually seems to be moisture issue. The other morning was cold but no moisture on windshield at all. Truck ran great. Rained and ran poor. Have changed plugs, wires and all coil packs, cleaned MAF and throttle body, Fuel pressure is around 48 at idle up to maybe 55 driving. No obvious broken or exposed wires

wow thank goodness my 1500 Silverado 94 and 1988 2500 doesn't have that problem either with a check engine light. But I do find this site useful I'm definitely will be looking up my cylinders this month

Did anyone figure out a solution to these problem I been having a misfire problem for months and need help on my 2004 avalanche

My 2000 z71 was doing the same exact thing and I put a 6in rough country lift on and it just went away lol there might have been a loose wire or something I don't know but that's what fixed mine

my 2006 gmc sierra has been doing the same thing for two weeks now, took it to three different mechanics and we cant figure out the problem, i have put new injectors, new spark plugs, new knock sensors, cleaned the throttle body out, the air filter was new, had all my coil packs checked out, replaced the evap sensor on the top of the motor and the charcoal sensor right next to the gas tank replaced, ive put a map sensor on it and i also put the new mass air flow sensor on it, took it to the muffler shop and my cat was destroyed they put a new one on the next day my truck had distroyed the new one, went back to the muffler shop and they tore the new one back off and the honeycomb was destroyed again, so i had them place the new one back on without the honeycomb, still running terrible, bad misfire, and the codes popping up now are running rich bank 1 and bank 2 and random misfire, seems like everytime i replace something another code pops up. has anyone figured out what the problem actually was.

I had a 2001 with the misfire and check engine light, but never noticed an issue with how it ran. I ran it that way for 60k miles without an issue. Got rid of it at 225k after I destroyed the transmission. Now my 2004 is doing it and the check engine light starts flashing if I go over 70 mph. Getting it checked out this week.

I have an 04 Yukon with the 4.8. Just 2 days ago, while on the highway, check engine light comes on and huge loss of power. Idles rough, but does not stall. Read codes 11 different codes. I pressed the erase code button on the scanner by mistake. Still runs like crap, check engine light back on, but no codes show up when scanned. 285 K miles. 2 weeks ago replaced plugs and wires. The plugs I replaced had a gap of .080 ". Yikes !

I have an 05 Chevy Silverado crew cab z71 and my engine was rough idling and I changed the knock sensors and wireing harness along with my intake manifold gasket now it runs with a smooth idle and gets way better gas milage also just an idea

none of these people that have the sAME promblen I do know no more than I do for they haven't fix theirs yet

I,ve noticed that a lot of silverados that have the little vacuum line going to fuel regulator on rail the elbow shape rubber boot must be factory defect because every time i work on silverados i check this and it turns out it as a real tiny slit or cut if you will thats almost invisible on the outside of elbow and when replaced the eng. light goes out and no more po300 .this was my results it might work for you if not it could be a different problem .

I had the same problem with random misfires on my 2000 Silverado 4.8. (Especially in cold weather) I changed the plugs wires tried swapping the coil packs around fuel filter and fuel treatments and higher octane fuel as well but nothing worked. I remove my throttle body and cleaned it and the ports for the idle air and the truck runs perfect. Honestly I would try that because I had the same problem for about 3 years( in cold weather or only)and my problem is solved!

Hey StepSideMark, That's great. I have found with a cold start with random misfires that go away as the engine gets warm could be the intake gaskets. On a cold start you can spray water near the intake gaskets. If the misfire gets worse, presto the gaskets are leaking. On the other hand a cold start rough running misfire on cylinder #4 and then may go away as the engine continues to run, could be the fuel pressure regulator leaking. Two ways to check this. First if the engine is already hot, just remove the vacuum line to the fuel pressure regulator. Sometimes fuel will spit out of the regulator. I have seen a leaking regulator not spit fuel, but after the engine is off for some time remove the vacuum line and fuel will drip out of the line confirming a leaking fuel pressure regulator. I hope this helps.

I have an 04 silverado 5.3 it started showing random misfires, ive changed the fuel pump, coils, spark plugs, wires, temp sensor, did a valve job because cylinder 7 has very little compression, checked MAF sensor, and we just put it all back together and its still running like crap it idles fine until you turn on the a/c or heat, the light blinks until im gassing it then it goes off but runs rough and wants to die anytime im idling... i dont know what the problem is has anyone else figured anything out

Go to the part house get u some Lucas gas treatment. I had the same problem tried everything. Treated my gas a few times no more problem. Most likely water n ur tank.every time it get to those fuel injectors make the truck misfire until they get tht water out.

F

Here is my experience with the random misfire? I love my 2005 Avalanche Z71 which I bought new and at 200k miles I had the engine rebuilt? Well for a month everything seemed great! Then I noticed at each gas refill, I had to put in a gallon of water in the holding tank for the radiator but could see no leak? Well, then I started to get a random misfire! It seemed to only occur when I was not using the air conditioning? I spent several months trying to see what was wrong? I suspected maybe the rebuild had a leaking gasket! Well, one day I had a kid who helped me move some old appliances and when we parked I looked back and saw a water leak? He said it was probably the air conditioning draining water? I said I did not use the air as it was cold! We opened the hood and lo and behold the heater quick disconnect lines were dripping water! He immediately said I need to fix it and by the way put something under the leak to keep it off the back ignition coil or I would have a random misfire! From the mouth of babes? Well, this is an improvement that Chevrolet fixed for us so we could quick disconnect the heater coil for replacement and which never occurs! These eventually start to leak sometimes as steam and you never see it and eventually as a leak! Well, the correct way to fix it is to cut off the quick disconnects and just put the hoses on with a clamp in the old fashion way! Thanks, GM? So I cut them off, put on clamps and no more leaks and no more misfires! The pros would have had me pulling heads! Get an opinion from an uneducated kid who can look and really see!

Pull your dist and look ad the drive gear. I've replaced min twice in 5 yrs and it was the exact same issues you're having. If I was driving through the neighborhood (25 mph) it would randomly miss. But the hwy or under load it was fine. The drive gears are soft metal and the cam eats em up.