5.7 Hemi Freshly rebuilt rough idle

[mrpineapple]

Hello all, I've been lurking all over these forums for about a week now and has come in handy several times. I am pulling my hair out over this pickup that I just bought with a blown engine.

2005 Ram 1500 with the 5.7 Hemi, it dropped 4 valve seats. I pulled the engine and sent it to a machine shop had them replace all pistons rings and bearings. They ended up boring the cylinders .030 over but the bearings were all standard and no need to grind them down. Heads had all new valve seats put in and all valves and guides checked (two valves were bent and replaced).

I got the engine back in the truck last week (I did all the labor except for the engine work) and went to crank it for the first time and it wouldn't start unless I pushed a fair amount on the gas pedal. It seems to run okay if I give it gas in the 2k-3k range it sounds okay but the idle is really rough. I drove it to get some fresh gas and treatment and it got slightly better with the idle but still isn't right. It makes no difference if it's warmed up or not.

Occasionally I get codes for both banks being rich and a cylinder 5 misfire.

So far I have checked/replaced:
Fuel pressure-steady at 58psi
exhaust back pressure- in the green (according to autozones rental tool)
Upstream O2 Sensors
EGR
New OEM Intake manifold+gaskets
Plugs (OEM copper ones)
Wires
Cleaned PCV
Double checked valve timing
No broken valve springs
All rocker arms move correctly
Compression at 100-120 psi for cyl 2,4,6,8. Will test 1,3,5,7 tomorrow. (I think it may be low because of the harbor freight compression tool not having a shrader valve on the spark plug fitting)
checked intake manifold gaskets for leaks

Today I pulled the plugs on one bank and noticed they were all wet, can't tell if oil or fuel. When I took the intake off I noticed a fair amount of oil residue, so I assume it might be that on the plugs.

Im thinking tomorrow I might replace the PCV and MAP sensor, but other than that I’m running out of ideas.

Also noticed today when I was pulled off the intake that cylinder 5 had some crap on the manifold. Picture attached, I cant tell if its carbon buildup or if it melted the plastic. Either way this happened with just idling and driving to the gas station <10miles. It was a brand new intake so all this just happened.

Any help appreciated! Thanks


Photo of Cylinder 5 intake manifold port

Video of engine running You can hear an exhaust leak, that I will investigate more tomorrow. Also probably notice the intake tube is off, the IAT sensor is still plugged in fyi.

 

[usaf2006]

Sorry man idk what to say, but good luck! Hopefully it turns out for ya.

 

[Andrew09HEMI]

Know it may sound dumb but what about vacuum leaks!?! Address exhaust leak to if its manifold it could be part of the issue as well.. The misfire leads me to believe there are worse things going on, especially with the build up in the intake manifold already, how do the other ports look?

 

[RonJon '06]

I would definitely do the compression test on the driver's side cylinders. After my rebuild the compression numbers were low too but I think it was because the rings hadn't properly seated. Some things to check would be the two vacuum lines that go to the throttle body, make sure the MAP sensor is seated and maybe try resetting the throttle body.

We had a member here a while back who actually had the plastic of the intake manifold melt from too much backfiring. Not sure but maybe the 30 thousandths overbore would require it to be custom tuned? I'm sure some other members will be along with some more suggestions and guidance. Welcome.

 

[mrpineapple]

SOLVED!

First thing I did today was investigate cylinder 5 misfire by doing a compression test on the 1,3,5,7 cylinders. 1,3,7 all good and 5 had zero compression. After some choice words I started to take the head off starting with the valve covers and just for kicks checked the pushrods again. Noticed that intake pushrod for #5 was outside of the joint and was wedged against the peak of the rocker arm thus not allowing the valve to shut all the way. This explains the blowback into the intake where it appeared melted. I reseated the pushrod and put everything back together and wallah! Runs like new!

I wish I would have checked compression first, I just assumed it was good from being a fresh engine. Lesson learned. I hope this post comes in handy for someone else thats going through a similar issue. I looked through at least 20 different posts of similar issues before I posted this one.

Thanks all for the suggestions!