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andrew93 07-28-2013 02:50 AM

02 4.7 rought idles dies
I just bought a 02 ram with a 4.7 had a blown head gasket and 3 valve seats dropped valve barley touched the top of the pistons also cylinder walls looked very good not scratches or marks. Took the heads to the machine shop and got them fixed them put the new head gasket and everything back together timing set right. Now my problem is the truck wont idle shakes and truck will not start unless i hold the gas to the floor also have a tapping/knocking noise under the intake. Any ideas would be great also im only getting 1 code and it is P1491 getting pretty frustrated with the truck.

RogerRamJet 07-28-2013 02:51 AM

Hey Andrew. Sounds to me like you've got a vacuum leak. I'd check all your vacuum hoses first.

andrew93 07-28-2013 02:59 AM

ive checked the vacuum lines i can see and all good but could be missing one ive had a few of these 4.7's and one i had to do timing on and it was a tooth off had a slight miss. So i triple checked the timing on this truck and it looked dead on and i would think if it was more them 2 or 3 teeth off the valves would be hitting the heads i could be wrong?

andrew93 07-29-2013 04:01 PM

Anyone else have any Ideas?

deanhinsley1963 07-29-2013 04:40 PM

Maybe do a compression test and see where your at.

andrew93 07-29-2013 08:30 PM

ok rented a compression tester from autozone im getting around 60 and 80 psi and on the cylinder on the driver side first one from the front is reading 0 when i had the heads off getting done at the machine shop the cylinders looked great still had the factory marks on them theres no oil and not smoking or anything

mb power wagon 07-29-2013 09:13 PM

if your getting a cylinder thats reading 0 on the compression tester you have a dead cylinder. also for the knocking under the intake double check to make sure you have all the push rods in the lifters. if i were you i'd pull the intake to see whats knocking and make sure all the rocker arms are moving before reinstalling the intake. it's a pain in the ass but you don't want to destroy the rest of the engine.

andrew93 07-29-2013 10:29 PM

i have the valve covers off now all of the push rods are were there suppose to be. also when i had the head off the block wouldnt i have seen problems if there was a dead cylinder when i had the heads off? the cylinder walls are clean and can see the honing lines

mb power wagon 07-30-2013 12:21 PM

not necessarily you won't see it if you have cracked rings unless you pull the piston out. for whatever reason your not getting compression on that cylinder. and the knocking can't be good. did you put a level across the deck of the block where the head goes on to see if it's still true? did you have the shop that did the heads double check to see if the heads were warped? the knock could also be a collapsed lifter.

LEW 07-30-2013 04:56 PM

If the "tapping" goes away after a few minutes, it's probably a lifter pumping up. If one of the cylinders is 0 psi compression, there must be a sizable leak on that cylinder. Seems like most of your engine problems were in the heads when you got the truck. Were the affected valve(s) reused, replaced or repaired (I'm not a mechanic, but repairing sounds risky depending on the extent of any damage)? Could be a valve(s) was damaged and not repaired correctly (maybe the stem is bent?) or the valve seat(s) was improperly repaired. The head itself could be damaged or the head gasket. Some BIG leak somewhere.

I guess it's possible enough of the compression rings could be damaged, but I'd focus on the head first.

If you're saying the other readings are 60-80 psi, that sounds LOW to me.

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