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Fresh 5.3 build now having issues running etc FIXED.now rear main seal issue

Vinnysdubs

Full Member
Joined
Feb 9, 2018
Messages
11
I have a 2004 Chevy Avalanche 2 wheel drive 5.3 engine, the original engine had a hundred and ninety eight thousand miles on it and due to a faulty water pump seal cracked head gasket the engine has been pulled and rebuilt another set of heads with a valve job new oil pump timing set rod bearings main bearings cam bearings rings and fully assembled once it was put back in the truck and started it was almost starting like the battery was dead or the timing was off but the timing marks are dead on when it was installed it's running now like it has a Miss in it which it did not have before and it also in the process blew the catalytic converters apart spitting the combs out the exhaust. it's throwing the codes PO174 po300 po135 I've replaced the coil packs the fuel rail and throttle body off of another known good 5.3 and I'm still having this issue with a miss and it still doing the rough start like you got the timing  really Advanced or really retarded. any ideas would be greatly appreciated of what might be my issue I've checked my intake gasket and of course it's new it looks fine I know the timing marks were set right all my wires are correct of course there's new plugs in it I just don't know what could be causing this issue also seems like 2nd injector from frt on pass side is not hitting pull off wire no eng change was reason I swapped the injector rail with a good one still doing same thing.punch it 4-5000 rpm eng light flashes let off gas sometimes dies sometimes not,clear codes punch it check eng light flashes again.
 
I suspect you need to perform the crank sensor relearn procedure.
 
Good call enoniam
 
I can try that .the eng in it now is the eng from it same crank and sensors etc.i haven't ran into this prob before.it starts just slow idles around 700 but has a miss to it,and for some reason it decided to start blowing the cats apart its weird how its acting oil pressure is great driving down road has good power but just not 100.no codes or issues before swap just a head gasket crack.
 
Question did you look at the o2 sensors when you changed the catalytic converters
 
they were fine before engine build no cat probs o2 problems or engine codes.all the problems started after installation of rebuilt eng. the o2 code came up with several misfire codes then the cat blew apart platinum and honeycomb everywhere out of exhaust. just wondering if I got a ground wire issue somewhere
 
as of right now kinda stumped. I haven't pulled exhaust or changed cats, o2 sensors or anything.just trying to run options on whats going on never had this problem with a swap before.
 
I would start having the cats checked it may have too much back pressure causing the P0300 and the blog and engine light.

The back pressure should be under 5 psi.
 
I shouldn't have any back pressure issue with the cats now. they blew apart there just empty cases now that it shot all the honeycombs and packing out the tailpipe
 
but im looking into buying 2 magnaflow cats and replacing the factory ones and new o2 sensors
 
Misfiring, low power, severe backfire in exhaust. Sounds to me like one cylinder isn't firing and is dumping raw fuel out the tailpipe. Do a cylinder balance test to isolate the bad cylinder then check plug, compression, coil, etc.
 
Vinnysdubs said:
but im looking into buying 2 magnaflow cats and replacing the factory ones and new o2 sensors
I'd make sure you sort out what the issue is before you install the new cats or you might get end up blowing them out too.
 
buickwagon said:
Misfiring, low power, severe backfire in exhaust. Sounds to me like one cylinder isn't firing and is dumping raw fuel out the tailpipe. Do a cylinder balance test to isolate the bad cylinder then check plug, compression, coil, etc.
there's no popping misfire sounds but I do have a fuel smell in exhaust and when I pull injector wire of 3rd cylinder from front on pass side no changes in eng tone I changed that whole side fuel rail and coil packs same issue never had this prob before not sure if a ground wire in starter or ground wire at bottom on front of block is causing it connection not good? As far as compression I can check it but eng has new rings rods mains cam bearings etc only 30 min run time on eng as of now. This a new issue I've never ran into before on a fresh eng.
 
frito said:
I'd make sure you sort out what the issue is before you install the new cats or you might get end up blowing them out too.
I plan on that just trying to figure out how this issue has happend from a running truck with a head gasket issue to fresh engine fresh heads eng is from the truck just rebuilt.to the problems now truck was covered in shop nothing got in it it did sit 4 mths due to finishing other projects to this issue
 
Vinnysdubs said:
there's no popping misfire sounds but I do have a fuel smell in exhaust and when I pull injector wire of 3rd cylinder from front on pass side no changes in eng tone I changed that whole side fuel rail and coil packs same issue never had this prob before not sure if a ground wire in starter or ground wire at bottom on front of block is causing it connection not good? As far as compression I can check it but eng has new rings rods mains cam bearings etc only 30 min run time on eng as of now. This a new issue I've never ran into before on a fresh eng.

Sounds like you've got a bad injector.
 
It could be as simple as a bad plug -- I've had a bad one out of the box before, probably dropped on the floor by a stock clerk. Check the easiest and simplest things first because a)they don't cost much time or money to check and b)they are usually the problem. If you have access to noid lights or a scope, check that injector harness end for power -- maybe a wire was damaged during the engine work. Check the injector resistance and compare to an adjacent injector. Check the coil output for spark. Check the compression on that cylinder.
 
Along the same lines, and not trying to insult anyone's intelligence, check for leaks in the intake system after the MAF.  I did a bunch or work on my 325i about a year ago.  The last thing I did was clean the MAF.  When I put it back on it missed and shook and threw similar codes to want you're experiencing.  Turns out I didn't properly connect two post MAF intake tubes allowing air to enter the system downstream of the MAF.  Took it off, realligned, tightened it up and it ran like a champ.

EDITED for major typos. 
 
ive swapped plugs checked intake for leaks,maf changed plugs injectors and coils. im wondering if a ground wire issue is the problem or the wiring in the starter causing a short ground prob etc.
 
went thru systems again and the injectors I replaced one was bad changed it and running good now.but after 300 miles on engine all new gaskets and seals the rear main seal started leaking not sure why are how so now ill be pulling trans out next week to replace that.
 
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