Good evening all,

I have a 1997 Jeep Cherokee Sport, 5-speed manual.

I recently did an engine swap over the last week as time allowed, the following video shows why, as it turns out, it sounded like top-end, rebuilt it from head up, including head, only to discover shortly after completion of that, the wrist pin in cylinder 5 was radiating noise through the engine, that broke, sending that rod through the side of the engine block.
https://www.jeepforum.com/threads/wh...noise.4480019/

I bought a new (to me) engine, here, https://www.ebay.com/itm/386303332848, I installed it, and now the RPM skyrockets at start to 3500 RPM and stays there. As far as I know, I have no vacuum nor air leaks, though this may say otherwise. This happens even with both throttle cables (foot pedal and cruise control) disconnected.

This has been a 3-month process, from vehicle stopping with Rod through the side of the engine block, to finding a new engine, to shipping, to time available to install (took a week wiht my limited time to get after it in between other things. This is my only vehicle and has been parked for 3 months.

Does anyone have any thoughts on this? Potential causes?

Thank you!

 

I'm betting the intake manifold isn't sitting right and you actually have a big vacuum leak.

 

Possibly, I did find this: https://wranglertjforum.com/threads/...en-loop.30631/ and this: https://www.cherokeeforum.com/f2/idl...tartup-219309/

Wranglers (TJ's) and Cherokees (XJ's) share the same engine in my year (1997).

 

I'll guarantee that intake manifold isn't fully seated and is hanging on a dowel pin.

 

I hope to check sometime tomorrow and report back that it's fixed, with this.

 

Been there, done that on the manifold not on the dowels. The last time I had this problem, the dowels seemed to be pushed too far in and made placement difficult. I measured the distance that the top of the manifold should be fromt he top of the head and made sure it was aligned right before tightening it all down.

 

As a few have said, but just to add to the likelihood, check your intake manifold. When I replaced my freeze-plugs a few years back and had the intake/exhaust off I was really surprised how easy it was to have the intake manifold not seated correctly.

 

Its quite a good idea to try and slip a feeler gauge in under some things that are supposed to be mated together

If one will slip in, you instantly know to go back a step

This has saved me quite a few times

The last time, my Jeep XJ LH front engine mount has dropped a nut, things seemed weird, and I could slip a .015" gauge in under the mount, so I knew there was a problem, I will relieve pressure with a jack and. and whatever else it takes to make it all good, as soon as my back stops aching from yesterdays efforts

 

This is exactly what it was. Uninstalled and reinstalled properly, all good.

This engine has a rod knock too.....gonna have to tear apart the lower half of the engine, maybe combine parts with the old engine to see if I can build a complete engine.

 

What kind of intake manifold gasket did you use? The cheap ones don't seal right and cause that, use a Fel Pro gasket.

 

No gasket is gonna seal if the intake manifold is being held away from the head due to hanging on a dowel pin.