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1999 suburban ck2500, 5.7l engine still has loud intermittent rap


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darckstorm
New User

Sep 21, 2014, 6:09 AM

Post #1 of 8 (1712 views)
1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In

Bought this 1999 burb a couple months ago with a severe rap (it seemed like upper end) this rap can go away completely and come back two minutes later. Pulled the motor and found 1 cylinder cracked and water in two cylinder with ersion on pistons. So I ordered a rebuilt 5.7L motor 4 bolt main. Installed it and it fired right up shut it down and finished installing everything else. Yesterday started the motor up and was letting it up to come up to temp and here comes that rap again. Its loud and can come and go. Re-checked all bolts on torque converter, again visually inspected flex plate all good there. Pulled the wires on the knock sensor since it was transferred, that didnt stop it. One of the things I thought it could be on the first engine was a rocker arm lose turning sideways rapping a while then setting itself again of course that wasnt the problem back then. My mechanic thinks its running retarded, I dont know. Hes put hes troubleshooting computer on it but its not sending power to his unit to read any codes. When the new motor was put in all new cap, rotor, wires, plugs etc were replaced. My mechanic says the distributor looks like its brand new so previous owner may have replaced it. Ive had a Chevrolet A mechanic say something about a holifax switch in the distributor. (dont know if my legs getting pulled im an old man an old school dont want to work on any engine unless its pre 72 lol) Why do they have to build these things with so much that can go wrong with them, they lost a lot of HP going to 1999 and an old one if properly tuned would get just as good a gas mileage. SIgh

Any help would be appreciated, first thing we are working on here is finding out why his computers getting no power from the plug in port

Greg


(This post was edited by darckstorm on Sep 21, 2014, 6:10 AM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 21, 2014, 8:01 AM

Post #2 of 8 (1688 views)
Re: 1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In

Did you transfer the harmonic balancer from the old engine to the new one?



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
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Sep 21, 2014, 9:32 AM

Post #3 of 8 (1682 views)
Re: 1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In

Does it rap idling, accelerating, decelerating, hot, or cold? Can you record the noise and put it up on a video hosting site and then paste the link in here? Check for power on pin 16 of the DLC. If no power, check the auxiliary power fuse in the instrument fuse panel. Record any trouble codes numbers.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Sep 21, 2014, 9:37 AM)


Tom Greenleaf
Ultimate Carjunky / Moderator
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Sep 21, 2014, 10:19 AM

Post #4 of 8 (1672 views)
Re: 1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In

What other parts from old engine were used on the new one. They can come different ways so you may have swapped the part and problem from the old one that made the noise but fixed the cracked problem?


T



kev2
Veteran
kev2 profile image

Sep 21, 2014, 11:01 AM

Post #5 of 8 (1667 views)
Re: 1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In

Check for power on pin 16 of the DLC. If no power, check the auxiliary power fuse in the instrument fuse panel. Record any trouble codes numbers. repeating what colleague suggested,,,, this is place to start...


the distributor was installed BY who? Without being able to communicate with PCM installation is suspect AND will likely produce issues and codes....


darckstorm
New User

Oct 3, 2014, 9:09 AM

Post #6 of 8 (1634 views)
Re: 1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In

Only part transferred from old engine to new motor was the intake. Since I posted this we have replaced the knock sensor, Spider injectors and tried a new ECM. All new wires , Plugs, Cap and rotor, camsensor. I dont want to have to take this to a dealership and pay out the wazoo. Since the spark knock was on the old engine and still on the new engine it has to be in something that was still on the car. Only thing Ive read so far is that there could be a vacuum leak in an intake port. So I am half tempted to pull the intake again and put new gaskets and sealant on it. Ive spent a ton of money replacing things and I have to be missing something. Even tried changing it to the firing order of a 479 cam and it didn't help. I will check the aux fuse and number 16 pin. I just know this is gonna end up being something stupidly overlooked, but I need to find out before any damage is done to the knew engine

HELP Any ideas will be appreciated


kev2
Veteran
kev2 profile image

Oct 3, 2014, 10:03 AM

Post #7 of 8 (1628 views)
Re: 1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In

stop spending money. diagnose don't guess.

you changed the intake manifold complete with injectors, and TB?
Explain the comment " Even tried changing it to the firing order of a 479 cam"


SUGGESTIONS
Get the codes.
do a fuel pressure test AND observe fuel pressure leak down...
I strongly recommend a scanner - ability to read live data - cheaper than the process you are using.


(This post was edited by kev2 on Oct 3, 2014, 10:07 AM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 3, 2014, 3:40 PM

Post #8 of 8 (1616 views)
Re: 1999 suburban ck2500, 5.7l engine still has loud intermittent rap Sign In


Quote
I dont want to have to take this to a dealership and pay out the wazoo.


I think you have already passed what it would have cost to have it diagnosed correctly. The dealer isn't the only one capable of doing this. I don't work for a dealer and I do stuff like this every day.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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