p0300 and p0308

[cxs4887]

my yukon (5.3) has been sitting for about 7 months it had a bad egr signal wire so the light was always on but i fixed that andnow it has a misfire code. it started as p0300 solid light to p0308 and at idle stays solid any accel makes it blink. plugs look good and the msd wires look good. havent checked resistance on them yet. im leaning towards maybe intake gasket? it is supercharged but only 8 psi tomorrow i will switch coils with another cylinder see if it changes to rule that out any other suggestions? maybe clogged injector from sitting and this garbage they call gas now a days

 

[SLCHOE]

my yukon (5.3) has been sitting for about 7 months it had a bad egr signal wire so the light was always on but i fixed that andnow it has a misfire code. it started as p0300 solid light to p0308 and at idle stays solid any accel makes it blink. plugs look good and the msd wires look good. havent checked resistance on them yet. im leaning towards maybe intake gasket? it is supercharged but only 8 psi tomorrow i will switch coils with another cylinder see if it changes to rule that out any other suggestions? maybe clogged injector from sitting and this garbage they call gas now a days

Could have a gummed up injector from sitting so long. Try tapping on the injector with a screwdriver while it is running to see if it frees it up.

 

[cxs4887]

would a bottle of injector cleaner be a waste of money?

 

[SLCHOE]

would a bottle of injector cleaner be a waste of money?

Not really. I clean injectors with a TerraClean system which runs solvent directly into the fuel rail (fuel pump disabled). That would work if the injector is in fact gummed up. Throwing that bottled stuff in your tank usually just frees up the varnish in your tank and sends it down to the injectors to gum up more of them. I don't suggest any of those "cleaners" you put in the tank unless your tank is new or very clean.

If you want to save the $$, pull the injector(s) out yourself and take it to a shop that has a bench top sonic injector cleaner. It's not expensive and is the way to go. Otherwise, take it to a shop and have all of the injectors cleaned on the car with a system similar to the one I use.

https://www.youtube.com/watch?v=wiViPKIoG68#t=13

http://www.terraclean.net/news.php

 

[cxs4887]

i have a small sonic cleaner maybe 2qt size would that work?

 

[SLCHOE]

i have a small sonic cleaner maybe 2qt size would that work?

You could try it. I was speaking more of an industrial specialized injector ultrasonic cleaner (https://www.youtube.com/watch?v=Baw_29n5vbM) ?

 

[cxs4887]

ill try it i dont think it would damage them then ill just run voltage to it and flush it out before re installing it

 

[cxs4887]

for those following this thread I tried today carb cleaner around the intake, no fluctuations in rpm so I don't suspect a leak. I also took out the #8 fuel injector, It really did not look bad but I cleaned it best I could and put it back in. with no results. still blinking ses light the only thing I have not done is use the old screw driver to listen to the injector is there anything I could be missing? ive heard a bad battery can have some affect is this true?

 

[ccapehartusarmyINF.(ret)]

not really plus if it could in thoery it would be affecting all cylinders not just number 8

---------- Post added at 03:16 PM ---------- Previous post was at 03:06 PM ----------

but id definatly check yer batterys voltage after the vehicle has been off for like 30 min
beucase i will say this i have abad battery cause a whole wide assortment if wierd problems like ive had a bad battery make the instrument guages and warning lights go all
it should hold a charge in the 12.4 to like 12.8 volts range then check all the charging systems grounds for hi resistance the ground under the front bumber the one to the block check yer alternator output voltage check voltage at the terminals

 

[cxs4887]

I'm at a loss with this engine is there a control module for all the coils that could have gone bad?