Hey I put a new set of heads on my 2.8 and since then it has been backfiring in the high rpms, i think it might be the valve lash. i don't have a cat on it so thats out and it has a new fuel pump in it. and the timing light says the timing is good.What do you think? I seriously think i screwed up when I was setting the valve lash.

 

High rpms as in 7000-8000? Becuase thats tooo high.

if its 5k-6k I wouldn't be sure.

 

not even 5000, more like after 3000 it starts backfiring violently, it blew the air intake tubing off the tb,but before 3000 it runs fine.i hope it isn't the valve lash cause thats alot of work.

 

Back firing from the throttle body? That has something to do with your valves

 

yea that sounds like valve lash to me, sounds like the intake valve is hanging up a little bit, try redoing the valve lash and remember tighten to 0 lash and go 1/4 turn more not 1/2, 1/4 turn. you should be fine then. if not, get your valves lapped in.

 

My 2.8 backfires while decelerating in lower gears. Sometimes I wonder if it's running a little too rich and the unspent fuel is igniting in the exhaust, or slack in the timing chain, perhaps? Probably time to change the plugs as well, since they've been in there for almost 1,000 miles...

 

is your car pop-ing or is it backfiring, cause poping is somewhat norma. check your timing chain for slack or play. install a air-fuel monitor to keep track cause it might be running rich

 

Yeah, sounds like popping I guess... I picked up a new set of NGK plugs. (never tried them before in this car, so we'll see what happens...)

The exhaust seems to smell a little rich, so I wouldn't be suprised if it was igniting in the pipes.

What are most likely causes for a rich condition? Leaky injectors? Bad o2 sensor?

 

there are alot of things in our cars that all work together to make the car run rich or lean. i mean there are sensors in the car itself around the ecm that contribute to that too. my car is running a tad rich but i am not worried about it, cause i would rather have it running rich than lean. i am slowly getting the problems solved to get it to run dead on(not rich or lean) but it is a slow ongoing process as there are so many sensors. those things cost a small fortune. i mean one of the things that i want to replace cause i know it is not working properly is tha MAF. they want 200-400 for a new one depending on where you go!

 

Found a problem... Well, two actually. Changed the plugs on my lunch break today. The wire on #3 was disconnected and the #5 plug was damn near falling out! This is what I get for not driving the car. She's pissed off at me!

Anyway, the popping is still there, but definately not as bad. The raw fuel smell in the exhaust has subsided a bit as well.

Funny thing is, the car did not seem to have real loss of power with the plugs in that condition. The idle was a little lopey, which I didn't mind, but I could still pound Hondas with little to no problem...

 

to help solve confusion.

AFTERFIRE = "poping" in the exhaust pipes from unburnt fuel igniting in the exhaust system. comonly called "backfire" wich is incorrect.
BACKFIRE = exhaust gas or burning fuel firing back into the intake.

backfireing is a MAJOR PROBLEM, commonly associated with valves that are sticking, heavaly worn, or mis-timed.

afterfires are somewhat harmless if they are small; and usualy just indicate a rich air/fuel ratio. however a friend of mine once had an afterfire so bad it split his cat. however this was in rusty stock exhaust on his 79 datsun with 400K+ on it.