Alright fellas. We just fresh built the 4.0l back to standard. Everything is new. Initially thought it was the timing but its correct. She idles smoothly but when you get on the skinny peddle it backfires through the exhaust and intake occasionally. Thinking fuel pump but haven't checked the pressure on the rail yet. Opinions?
04-28-2013 08:20 PM
Did you lap the valves? If not the have to seat in.
04-28-2013 08:27 PM
Took them out one at a time replaced the seals and lapped them
04-29-2013 07:58 AM
04-29-2013 08:16 AM
04-29-2013 09:43 AM
not throwing any codes...was hoping that it would throw an o2 code and it be an easy fix....NOT!
04-29-2013 11:00 AM
New rocker arms? Curious if you got the right ratio.(shipping error) usually if it back fires through intake ,valve is still open on combustion.
04-29-2013 06:21 PM
Original rocker arms and valves... Just had the seats and seals done checked the fuel pressure today and everything is fine
04-29-2013 06:29 PM
How old is the gas? I know my small engines start the crap when I got bad gas.
04-29-2013 06:31 PM
Also fresh....I really don't want to admit defeat and take this to the shop
04-29-2013 06:38 PM
Know your pain. Is there a flame coming out with the tail pipe back fire. Might be a vacuum leak? Try.a good can of carb cleaner on all gasket seams.
04-29-2013 07:00 PM
No flames. She idles soooo smooth and is solo quiet....no vacuum leaks...I think it's possessed
04-29-2013 07:27 PM
Sounds like cam timing to me. Timing marks aligned right?
04-29-2013 08:56 PM
Yeah. Even pulled the cover and reset to tdc and recheck distributor timing....it's perplexing