350 vortec miss

racin90

racin90

Well-Known Member
Ok..never have seen this before...just picking some minds. Have a buddy..who has a 96 chev p/u...started his truck and it just started missing. Has 100,000 miles on it. We put all new plugs cap rotor wires...ect..still misses on #5 cyl. did a compression check..its within all the other cyl's. Checked cam..all is ok. Weswapped plugs with the other cyl's...still #5 is dead. Check engine light blinks says #5 cyl misfire(no joke..lol) so..its gotta be something electrical..anyone ever had this happen?? Im getting a manual and going to sit down and read it this week..just wondering if anyone has ever come across a later vortec with a miss issue....thanks.
 
hmmm i have never seen that but i agree,i would start chasing and checking the wiring,or the computer is starting to fail!
 
injectors

these are notorious for haveing bad injectors the way that these are setup is they are located underneath the throttle body the upper half of the intake has to come off and these are referred to as spidervalves because all of the injectors of together and replacing them are not cheap. like i said these are horrible for having this problem

mike
 
i have had to repair spidervalves when i worked for gm goodwrench,be prepaired they are not cheap!
 
Mike I know this sounds crazy but it actually happened to me with the same truck. 96 - 350 vortec. The greeen anti freeze eats away at the aluminum intake on these things. Wen that happens of course you get antifreeze in places it doesnt belong. it just so happened mine was going into the cylinder and fouling out the plug. crazy I know. But, it really happened LOL!
ORRRRRRRRRRRR.........
Is it on coil packs ?
when you swapped plugs did you also try swapping wires ?
 
i would start with a compression check on that cyl. if ok, i would look real hard at the fuel pressure regulator. they are notorious for leaking. when they start leaking bad enough, they will cause a misfire on #5 cyl. the way it's located inside the manifold, when it leaks, it dumps right down #5 cyl. intake runner. art.
 
RaceGoddess said:
i would start with a compression check on that cyl. if ok, i would look real hard at the fuel pressure regulator. they are notorious for leaking. when they start leaking bad enough, they will cause a misfire on #5 cyl. the way it's located inside the manifold, when it leaks, it dumps right down #5 cyl. intake runner. art.
Click to expand...
I agree with Art (pretty good for a VW tech Art.LOL)
 
hey howard... i am multi-lingual!!! haaahaaa. do you still have that quarter midget??? i think you need to drop that off at dean's. i will give it a nice, happy home!! art.
 
Hey..thanks guys. Just got some tips from a buddy at the gm parts counter...told me same things...look for antifreeze issue..injectors and fuel regulators leak. Not bad guys...thanks again. Im getting the truck left here next week to work on..so..ill let you know what i find..or..better yet..what i dont find...lol
 
you might try to clean the injectors first before you tear into it.
We fix a lot of them with a pressurized cleaner.
 
Thanks to all who replied. Replaced injectors(they were really cruddy looking) and ran injector flush into the lines(took it to a shop for that.) But..unfortunately...we are too late because it seems...it has a small hole in a piston(probably due to cruddy fuel or the injectors leaning the cylinders out). Thanks again
 
that's why you always do a compression test (or better yet, a cyl. leakage or leakdown test) first. if you have low or no compression, no amount of injector or spark plug replacement or cleaning is gonna help. do the basics first... always. glad you found it, though.art.
 
Yea..its my boo boo...i just couldnt see it having a burnt piston with the miles this thing had. He is having me do the engine replacement and isnt disappointed at all. Like he said...heck..i would have to have replaced them anyway since they were pretty much junk..but...you are correct..and i used the ASSUME mode in my diagnostics. Thanks again for the info
 
I use a Snap on MODIS, Where is the ASSUME BUTTON located?? ALWAYS CYA!! "Well, Sir, I've found a bad injector, and, AS LONG AS THERE ARE NO OTHER PROBLEMS,it SHOULD be around $XXX".!!!


ASE Ask Someone Else LOL Greg
 
I realize...my booboo..but..this was also done on my free time..with the customer there..was kinda his decision as well. I graduated from the BYA school(bust your astronomicals) and been doing this for 25 years. Ive seen some ASE guys we have hired that couldnt even zip their own fly...so..to me...that means nothing. He is happy..and realizes what was going on. Like i said..i know...what i was doing..was off the wall..but..i work 55 hrs a week..spend time with my 2 kids..and wife...and things like this i do quick..and as simple as possible.
 
90,Just some razzin,couldn't resist,I've been there.I also agree, You can teach any body to pass a test,and trade school is good for a little theory, BUT that doesn't mean they can fix a car. Seen it too many times. I'm sure your customer appreciates your HONESTY, and will remain loyal. By the way, I had my wife remove all the zippers and install Velcro.ALOT easier for us ase guys. J/K
Greg
 
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