I have a 98 Disco that i just changed out all gaskets, new o rings on injectors, cleaned of all carbon buildup of valves, rockers and lifters. After a week of driving it check engine light went on and started to tick quietly (when accelerating it becomes more of a knocking) following with a loss of power. Upon checking codes cylinder #3 said to be misfiring and other random misfiring. I checked my oil pressure and it was 29-28psi cold 34psi @2000rpm, 8-9psi hot 25-27psi @2000rpm. Cleaned out my oil pick up and tube to the oil cooler which improved the pressure slightly, but not fixing the problem. Then I checked all my spark plugs to find out that #3 and #8 seemed to be more black and moist than the other 6 light brown colored spark plugs. After checking for spark they all seem to work, then for grins and giggles i disconnected cylinder 3 and stared the engine and the noise disappeared. Im stuck with no more ideas....help

 

You are below spec on oil PSI. My oldie makes 44 PSI. Spec is min 10 PSI hot, 30- 40 PSI at rpm. Are you running 15W40 Shell Rotella? Could also have cracked oil pump....

Would think that if knock goes away with plug wire off the connecting rod may be involved. A quick thing to try on oil is a different filter and more different oil, if you are running 10W30 or such now. Seems like your wrenching days are not over yet.

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Stop driving it and first tear down/inspect and replace the pump. At the same time time to inspect the crank and rod bearings.

 

What's the mileage on the motor? Soot on plugs usually leans towards those injectors. Might have intake vacuum leaks at those intake ports as well. 35Nm does not keep intake manifold bolts from loosing with a couple of heat cycles.

Did you clean out the rocker shafts and rocker oil ports? Instal them with cotter pin in correct position to line up oiling with the rockers? Knocking is most likely from those two cylinders.

Was the motor running better before you did the work? Clean carbon off piston tops too? Any thick tan deposits on pistons cause hot spots, can pre-det when motors warm and knock sensors won't compensate.

 

It has 120,000 miles. It ran good for a little over a week and then it started ticking, and yes I did clean the piston tops and the noise is coming from cylinder #3 and #8. Right now I am running 10w-30 after I did an engine flush twice with BG Sluge Remover removed my oil pan cleaned out the oil pick tube again and then ran some Sea Foam.I understand my oil pump is running below factory specs and I will replace it but my ultimate question is why is there no knocking noise when plugs are disconnected from those 2 cylinders?

 

Could be that stress on the rod bearings is reduced by piston not firing.... but put some 15W40 in and see what your pump can do. 10W30 in a Disco is good for below 95F operation, hard to find that in stopped traffic these days...

 

Just checked out my rod bearings and they are worn out to the copper, just bought new ones and new main bearings. Is there a way to change out the main bearings without removing the oil pump and timing chain cover?

 

make sure the crank surfaces arent wasted as well before you just go throwing new bearings in there....

 

How would I do that?

 

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