2.5 engine problems - JeepForum.com

 
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post #1 of 15 Old 09-28-2010, 06:31 AM Thread Starter
2005LJRubicon
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2.5 engine problems

Ok so i have 2.5 with 125k on it. On my way home from work running down the highway the motor was turning about 2800 to 3000rpm. I started to notice a really bad valve tap. I know all the 2.5 sound like a sewing machine but this was way worse out of no were. I also noticed that the oil pressure gauge wasnt were it normally at speed or at idle. When i got off the highway and put a load on it at lower rpms it also started to miss too. What are your thoughts. I just got this thing as a beater and not looking to put alot of money into it.


-Aaron
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post #2 of 15 Old 09-28-2010, 06:35 AM
schaef89
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maybe you're oil pump is going bad. Is you're oil pressure higher or lower? If it's not creating enough pressure there would be a decrease in oil to the valves in the top end of the motor.
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post #3 of 15 Old 09-28-2010, 06:44 AM Thread Starter
2005LJRubicon
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lower but would that cause a miss as well.

-Aaron
2005 LJ Rubicon 3inch lift genright tubes, 35s
1978 CJ-7 SOA 33s and a 304
& gfs 2002 TJ Sport w/ 4'' lift & 35'' mud tires
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post #4 of 15 Old 09-28-2010, 06:59 AM
schaef89
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not sure about the miss but that would def cause the valve tapping noise. It's possible that two things went bad at the same time. Is this a TBI or MPI 2.5
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post #5 of 15 Old 09-28-2010, 07:04 AM Thread Starter
2005LJRubicon
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mpi

-Aaron
2005 LJ Rubicon 3inch lift genright tubes, 35s
1978 CJ-7 SOA 33s and a 304
& gfs 2002 TJ Sport w/ 4'' lift & 35'' mud tires
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post #6 of 15 Old 09-28-2010, 07:07 AM
jsawduste
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Quote:
Originally Posted by 2005LJRubicon View Post
lower but would that cause a miss as well.
Sure, if the lifter(s) were not getting oil then they would not be opening/closing the valves properly.

Welcome to an engine that needs attention.

You did check the oil level, right ?
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post #7 of 15 Old 09-28-2010, 07:17 AM Thread Starter
2005LJRubicon
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yeah right where it should be

-Aaron
2005 LJ Rubicon 3inch lift genright tubes, 35s
1978 CJ-7 SOA 33s and a 304
& gfs 2002 TJ Sport w/ 4'' lift & 35'' mud tires
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post #8 of 15 Old 09-28-2010, 07:20 AM Thread Starter
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also i should add that it never went below the normal rule everyone seems to follow. It had around 10psi for every 1000rpm or at least close.

-Aaron
2005 LJ Rubicon 3inch lift genright tubes, 35s
1978 CJ-7 SOA 33s and a 304
& gfs 2002 TJ Sport w/ 4'' lift & 35'' mud tires
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post #9 of 15 Old 09-28-2010, 04:51 PM
Mark05059
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drain the oil and remove the oil pan. clean the pickup of the oil pump change the filter reinstall the pan with a new pan gasket and fill it back up with oil. See if that does anything for you.

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post #10 of 15 Old 09-28-2010, 06:17 PM
moonshinefuel
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I would check the oil pan for spun bearing material for sure. Hopefully that's not the case, but, these oil pumps are pretty solid, and last a long time. As Mark05059 states, check the pick-up, maybe its clogged. If your oil pump is good, and oil pressure just dropped out, from nowhere as you state, and then missing, and noise..it sounds bad. But this is just an opinion from a breif description. If a crank bearing bit the oily dust, that is a possibility for having oil pressure drop out, and running bad.
At 300,000 plus thousand miles, I do not bring mine to 3k rpm and hold that on the hiway. I hold it around 2.5k rpms. I have an old squirrel, no sense in pushing the furball too hard on the highway. Off road, no need either, keep it in 4low, and the rpms need not be that high at all to traverse the things that I do. Good luck, hope things are not that bad.
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post #11 of 15 Old 09-29-2010, 06:44 AM
vanwyk4257
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Yeah, definitely check for any bearing material. I had a Porsche 944 track car and noticed the exhaust note was off just after passing pit in at a road course event. By the time I got back around the track short shifting to keep the revs as low as possible the damage was already done. The possibility of a spun rod bearing is nothing to mess with. I lucked out and it hadn't done any significant damage to the rods or case.

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post #12 of 15 Old 09-29-2010, 07:56 AM
schaef89
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i have a bad rod bearing (knock) and it doesn't have any symptoms as previously stated. Been driving it for 60000 miles and counting. A bad bearing isn't going to affect oil pressure unless the shards are big enough to block the oil pickup and the ones i've seen have been no bigger than a grain of sand. Even so the filter should pick them up before a drastic drop in oil pressure is noticed.
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post #13 of 15 Old 09-29-2010, 08:21 AM
vanwyk4257
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Your statement isn't entirely true shaef89. It likely depends on the oiling system in the motor in question. In most cases a bad rod bearing will affect oil pressure. Frankly if you've been knowingly driving a vehicle with a bad rod bearing for 60K that would at best exhibit poor judgement. The problem is once a rod bearing goes bad the rod starts to hammer back and forth, hence the trademark "knock". Sooner or later the rod or hardware will let go. It's not a question of "if", but of "when". I'm not trying to call you out, but I find your claim of 60K on a bad rod bearing very hard to believe. My assumption would be you have misdiagnosed the problem and it's something aside from a rod bearing causing the noise.

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post #14 of 15 Old 09-29-2010, 09:06 AM
schaef89
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no offense taken, I totally agree that it shouldn't be driven under those circumstances, but i did not have the means to fix it as i was in school at the time so "drive it til it dies" came into affect there. I noticed the knock shortly after i bought it in 06 at 93000 miles, then dropped the pan to inspect. The bearings were pretty bad and i saw brass shavings in the oil so I just replaced the bearings with new ones and started using 10w-40 in hopes it would hold out until i could fix it right later. It now has 150000 on the odometer and hasn't blown yet. I realize it's hard to believe but its survived almost 5 years and 4 hour trips back and forth to school for 4 years.
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post #15 of 15 Old 09-29-2010, 09:17 AM
vanwyk4257
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Quote:
Originally Posted by schaef89 View Post
no offense taken, I totally agree that it shouldn't be driven under those circumstances, but i did not have the means to fix it as i was in school at the time so "drive it til it dies" came into affect there. I noticed the knock shortly after i bought it in 06 at 93000 miles, then dropped the pan to inspect. The bearings were pretty bad and i saw brass shavings in the oil so I just replaced the bearings with new ones and started using 10w-40 in hopes it would hold out until i could fix it right later. It now has 150000 on the odometer and hasn't blown yet. I realize it's hard to believe but its survived almost 5 years and 4 hour trips back and forth to school for 4 years.
That makes a little more sense. You may have caught it early enough that there wasn't yet damage to the crank or rods. I think we're on the same page.

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