AirMan

Hello everyone......hopefully someone can see what I am missing and provide an answer. The truck in question is my backup truck and I use it just 1 or 2 times every week or so. It has been running perfectly without any issues until the other day. It has started to misfire. The basic scanner tells me that it is the dreaded "P0300" code which equates to random misfires. I have replaced the plugs and I checked all the wires. I have even replaced the coil. The truck runs rough in "Park" but when I put it in "Drive" it gets worse...in fact you can hear the misfire through the exhaust. For a couple of runs, I got a #4 cyl misfire but then it went back to random. Any ideas?

new2me

Fuel pump comes to mind.Cap and rotor,MAF sensor.check fuel pressure to at least eliminate that side.You are in the years where the fuel pumps are a P.O.S.

suzuki-guy

FUEL FILTER? Gary is right only use ACDelco parts!! Also look at catalyst converotr after it is warmed up to see if it is glowing orange which would indicate it is cloged! a good way to check EGR valve is to hook a vaccum pump up to it appy vaccum if it gets worse the EGR is good if nothing happens EGR needs replaced! You can check MAP sensor with a voltometer. Check vaccum lines for crakcing also!

new2me

It may also be the ECM.Does the check engine light flash or just stay on?

bronzebogen

Airman, I'm curious to see if you found a solution to your problem yet. Did you get it fixed and if so what fixed the problem? I'm having a similar issue with mine and am searching for a solution. If you were able to fix it I'd be grateful for any hints! Thanks.

AirMan

Hello everyone....sorry for the delay I was out of town. I changed out the cap and rotor and that fixed the problem. The old parts looked fine and the only thing that I saw was that the cap had some kind of oxidation around the posts. Truck is running strong. Thanks for everyone input.......

Imuz me

I'm having the same issue. I get codes P0102 (maf) and P0340. I have cleaned the MAF, changed out the cap, rotor, plugs and wires. Runs worse now.. Been chasing this for 2 mos. About to throw in the towel and take it to the shop.....
Mind you it started out of the blue.... 120K on 99 Tahoe.

jammin777

[quote=new2me;95156]It may also be the ECM.Does the check engine light flash or just stay on?[/quote

hi, i own a 96 chevy k1500 5.7 vortec auto trans,
i have a misfire in cylinder 5. heres what ive done so far, new cap and rotor, plugs and wires, induction clean, compression cks out at 150 psi ck for vac leak, i have done everything i could think of and still have the missfire in cyl 5, it is worse when cold and almost goes away when at op temp the ck engine light sometimes flases and most of the time stays on sometimes it turns off by itself.
with a otc genisys scanner i get code po 300 then i go into missfire stream ant it shows cyl 5 misfiring when cold the cnt is around 200 when warm the count drop to 45 any help would be greatly appreciated as ive ben chasing this for over a week,

f-bodyfreak

if your getting the multiple misfire this is a couple of things iv found bad pcv valve witch caused it to suck oil into the throttle body and sludge up the intake and valves remedy clean intake and throttle body next in line leaking intake gasket or throttle body gasket spray the motor around the intake and throttle body with carb cleaner if idle goes up theres a leak next clogged injectors and the out of the bottle quick fix doesnt work it makes it worse by taking all the garbage and running it threw the injectors from the gas tank up to the very small holes out of the injector have them cleaned by someone with a injection cleaning kit

whiskey1

1996 chevy k 1500 5.7 new intake gasket complete tune up mass air meter
mis on no 4 after warm up great when cold any ideas