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knocking engine on cold start at lower rpms?

ybreal210

NAXJA Forum User
Location
Jackson, NJ
so i recently got a 93 xj with a 4.0 5spd 4x4, and lately when i start the truck and its cold, for the first few minutes when im driving at partial throttle in 1st & 2nd gear from 1500 to 2200 rpms im getting a knocking sound, sounds like a rod knock but i thought a knock would stay consistant not come and go, i thought maybe someone could give me some ideas to check. The truck has excellent oil pressure and once its been running for 10 - 15 minutes the noise is gone completely til the motor cools down again...
 
So, cold start, when just idling there is no knocking?

What oil viscosity are you running? What brand oil filter?
 
Probly a lifter? i'm by far not a mechanic just a backyard hillbilly. But i do know that the 4.0 is famous for lifter noise. I had that problem too. I remidied that with two clarion 12'' subs :yelclap:
 
Sounds like the same thing I have but mines all the time now even hot. I was told its block flex. I put some lucas in it and it seems to help but im going to try some 20w-50 next oil change with lucas to see if that helps. I have a 93 also...
 
yes its only on a cold start, im runing 10w40, i dont think its a lifter it sounds lower end, it does not occur at a dead idle, it only occurs from the 1500 - 2000ish rpm range for the first 5 - 10 minutes of running, if i start the truck and let it idle for 10 minutes it doesnt make the noise either.... thats why im completely stumped
 
Depending on how cold it gets, might think about switching to 5w or 0w weight oil.
 
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