Topic: New Engine ... loss of power...

[dunklervogel]

Long story short:  Had to replace the engine in my '97 tj .. went the cheap route and got another 2.5.  Was supposed to be exactly the same but the exhaust manifold bolt pattern was a bit different.  The mechanic installing the engine somehow got around that though.. and that was the only issue.  So I guess the installation went pretty smooth.

Now I've had the jeep back for around two days and have driven it about 50 miles so far on the new engine.  I have been experiencing quite a noticable difference in power compared to what I had with the old engine.  They are supposedly the same, so I'm confused why this would be happening.  Everything under the hood was completely stock and it still is besides that new engine (which is supposedly identical to the old one) If anything I expected a slight increase in power from a newer engine.. maybe getting back some extra HP lost from age and use from the old one.

The best analogy I can give is .. it feels like the air condition is on all the time... even though it is not.  You guys know how much the AC on a 4banger drains the power...  yeah it sucks!  ....  Now the AC is not even hooked back up yet so I'd hate to see how it drives with it turned on now.  Seems to have lost a lot of low end torque (if that is what puts u back in your seat when you are taking off).

Now.. I've been told that this problem might get better with time when the new engine is "broken in" a little more.  I hope so!  I just wanted to post this issue i've been having here to see what everyone else thinks.  I'm not very mechanically inclined but I'll try my best to answer any questions if someone wants to know something I haven't talked about here that may help ya figure out whats goin on.  Thanks in advance!

edit: Guess I forgot to add that besides the loss of power everything seems to be working fine.  It sounds good and runs good.

[Jeffy]

What exactly was changed?  Sounds like the block wasn't the only things that was changed.

[dunklervogel]

I'm pretty sure it was just the block maybe a few extra things... the crank case and other inside stuff was shot but all the other things like alternator radiator etc were fine and kept.

There were two different options frmo what I was aware of.  Just the block, and the block with some extra stuff with it.  The second option cost a little more with the extra parts.. but it ended up being cheaper going that route than it would have to detach and reattach these parts frmo the old block (labor costs would have brought the total higher in the end)

 wish I had more info I'll try to find out more later.

[dunklervogel]

Another thing that prolly doesn't matter at all is .. the clutch got replaced as well.

[Jeffy]

So they reused your old head?  I don't see why there was an exhaust manifold problem.  I believe the only difference is in the manifolds and not the head bolt patterns.  Was the block a new core or a rebuild or was it just a swap?  How many miles are on the engine since you got it back?

Have you checked the PCM for any codes that didn't trigger the CEL?

[dunklervogel]

The block was a rebuild and yes I believe they used the old head.  Haven't checked the PCM since I got it back.

As far as miles on the engine It got replaced at almost 94,000 and now is just a little above 94,000 .. so yeah not much more than 50 miles on the new engine so far.

[jcsanders79]

I also had the unfortune of rebuilding a 97 2.5L. I the same problem with power once I got the the Jeep back.  The oil pan was different and that was it.  I am not sure but I think that all of the 2.5L blocks are internally the same and the only differences are the bolted on exterior parts.  The good news is that once I put some miles on the engine the power increased.

[dunklervogel]

Ok thats good to hear.  I'm hoping that will be the case with me.

Just checked for codes through the ignition and got :



12      Direct battery input to PCM was disconnected within the last 50 Key-on cycles.

and

46      Battery voltage sense input above target charging voltage during engine operation.



Niether seem to be a big deal... 12 seems normal after being worked on and no clue about 46.  But even if I do have to put some miles before power starts to return, I really have to wonder why that is?

[dunklervogel]

Just curious but do you remember how many miles you had to put on the new engine before it wasn't so bogged down feeling?

[jcsanders79]

I think it was just after 1000k?  That is right after the first oil change.

[Tall Boy]

i got 100,000 miles on mine and It is running fine. i am hoping I will not have to rebuild mine soon. It still is withing tolerance on a compression guage though.  I got 180 psi, 175psi, 172 psi , and 165 psi , out of all the 4 cylinders. i hear that the two closest are measured for gaps in psi , so 8 psi difference is not that bad.

[dunklervogel]

My old 2.5 had all sorts of problems.  I'm like the third owner though. Oil pressure was terrible... it was eating antifreeze and I had to refill the radiator like every 2 weeks. Rods were bent and had to replace those.  The crankcase was the last thing to go.. and when it went to hell that did the poor thing in.  Kinda sucks too because it ran just fine up until it self-destructed  :roll:   Figure since the 2.5 engine doesn't have a reputation of being unreliable.. I think one of the previous owners just ran it hard and didn't take very good care of it.  Possibilly with little or no oil on occasion or something.

[jcsanders79]

The local Jeep shop that rebuilt the engine said that they have seen a few early TJ's with the 2.5L that needed to be rebuilt.  Mine only had 103,000 and it threw a piston with no warning.  I was on the interstate heard a noise and before I could get to the emergency lane the engine lost all of its oil.

[Tall Boy]

I have been fortunate enough to become religious with my maintenance. I also do not go offroading very often anymore so there I am. This has been  my daily driver for the past 5 years. If a good for nothing,loser  thief does not get it, hopefully it will last a long time.

[dunklervogel]

Well I've been driving it a little more and have to say it is starting to get some pep back already.  Around 200 miles on the new engine now.  

One weird thing I noticed is I found it had a started getting a little more power just 30 miles or so after filling up on gasoline for the first time since it was back from the shop.  If for some reason there was bad gas in the tank would that have any effect like what I've been experiencing?  Just something that popped in my head.  

Either way.. glad to see this wasn't a permanant issue afterall... and this situation might be good to know about for anyone rebuilding / replacing their 2.5 in the future.