hey guys.. gonna start with this site has been very helpful and i've been on it many many times... finally have a reason to make a thread. i'm probably just overlooking something but here's my problem that i need help with. please throw out any ideas or advice, thank you

92 3.1 is backfiring in intake. everything is stock
sounds like a lifter issue goin on too
cant tell if its backfiring at idle.. but definitely when throttle is opened.
have pulled the pushrods out and replaced all bent ones last month, one was very bent. sounds like it has developed another bent pushrod so when the parts get here i'll be replacing lifters and pushrods again.
fuel pressure is good at rail with new injectors from southbay and they are getting signal.
timing is correct, set with computer unplugged and a timing light.
no codes



youtube video:



this is the list of what alls been replaced within 4 months. the car was a no start, no fuel, no nothin when i got it.. have gone through the several issues getting it back up and running. not in order.. just stuff i could think of
New tps sensor
New map sensor
New coil
New pick-up coil
New relays
New distributor cap and button
New fuel injectors
New intake manifold and valve cover gaskets by fel-pro
New fuel pump
New wires
New spark plugs
Good battery
New various bulbs
New fuel filter
New ignition control module
New idle air control valve
Intake manifold cleaned
Throttle body cleaned
Distributor cleaned
Fuel tank cleaned


craigslist post i made of the car, hoping that i can fix it and keep it but this is plan B.

http://norfolk.craigslist.org/cto/4287561320.html

 

If you had bent push rods it doesn't sound like it's directly connected with the stuff you've done. What's been done to the engine? Are the lifters and push rods etc. stock? Cam? Is the timing set right? Stock tune etc.?

 

the list is due to the train of problems it's had. not just the backfire issue. it was a no power no start no nothing car when i got it and have been chasing down tons of things haha.

everything is stock. anything replaced is a stock replacement. i would love to put a new cam in it but i want to see thing run like its supposed to first lol.

 

Bending pushrods on a totally stock engine is almost always a binding rocker or valve ....

Now , for the obvious question , what are the compression readings of each cylinder ? If you have not yet done a compression test , that should be your very next order of business .......

 

[QUOTE=init4fun;5708580]Bending pushrods on a totally stock engine is almost always a binding rocker or valve ....

I agree. If you are bending a pushrod, there is something else going on. If your intake valve is bent or is not seating correctly, then it will definitely cause the backfire you are having.

Do the compression test, if you don't get a good reading, then you'll probably need to pull the heads off. I've seen problems before where someone dropped a nut down into the intake, which then got down on top of the piston and caused a lot of damage to the piston and valves.

Another thing to look at is your valve springs. If you have one that is broken, a lot of things will go wrong.

 

Alright i had lifters ordered so i went ahead and took it apart. Figured i could crank the motor over too and watch everything to see whats goin on. I did find the noise, 2 rocker arms were loose. All i had time to look for.. Gonna work on it some more tonight.
This is where its at:




Yeah ive done multiple compression tests since i got it to track it. Got the most recent ones somewhere...



I'll post back when i get home with specifics on what i found last night. Oh i do remember there was some fuel leaking from the fuel pressure regulator... So need to look around for a new one of those too

 

uncovered it and took a look.. got a bad lifter on intake side of #5,#3,#6 cylinders.
this is just from looking, not pulling the rods out and taking them out but its pretty freakin apparent the lifters have come apart lol.
i dont want to pull them out until the new lifters and rods get in my hands.

gonna go ahead and replace em all so it'll be done and out of mind for a while. i know how to prime lifters but i'm not sure if these V6s need the tappit side coated with grease or Molykote or whatever?

 

nvm...

 

It's not an unheard of practice and it's quite successful actually. Going to go with it and make sure the cam lobes are ok, check the lifter bores, oil the lifters, rub a generous amount of break in lube on them and the cam lobes, treat it to the same process as breaking in a new cam.

Got the lifters today. Planning on pulling the rockers, rods, and lifters to inspect everything. Found a tolerance chart so i'm ready to lay everything out.


Aaaand it's raining. Soo all thats on hold lol

 

Couple of ideas, when you put the break-in lube on the lifters, don't get any on the sides of them. Only on the foot. Oil on the sides so that the lifter will spin on start up.

While the distributor is out, remove the cap & rotor. Grab the gear and body with one hand and grab the star wheel up top with the other hand. Check that the star wheel (6-point) is tight to the shaft. It must move with the shaft, if loose that is an issue.

Since we don't know what has been previously done, I have a feeling that the valve lash may be incorrect. Lots of sources state to just torque the rocker nuts down. Not so on our 3rd gens.

They get lashed just like a SBC (and BBC at that).

RBob.

 

dont just replace the lifters , call up delta and order a 252cam and lifter set its only 105$ shipped,
if the original lifters were bad chances are it damaged the cam lobes , specially since u were bending pushrods

and yes if done properly there is nothing wrong with replacing only lifters

on the other hand u cannot use a new cam with old lifters

 

Yeah that makes sense Rbob, I greased the feet and tried not to make a mess. Used as much as i could too.

Checked the distributor, seems fine as far as any looseness goes, thing is showing its age though

All of the old lifters were seized and some came apart, i have all the pieces.





These were the worst "x"


Got the rockers back on, loose.
Intake manifold is back on and snug
Gonna finish up and tighten/torque everything down tonight. Didnt have time last night

Oh and the cam looks okay, only saw one lobe to keep an eye on

 

Did this fix the backfiring issue?