225 v6

Have my first jeep, and am now worried about the 225 that is in it. It has a low rpm knock only after warming up. It goes away as soon as I give it a little gas. other than that it runs great! It does have a miss when I first give it gas but other than that it doesnt miss a beat and has pretty good oil pressure. Any ideas on whats causing the miss or the knock?

 

Could likely be a rod bearing. May not be that bad if it is. I had a rod bearing fail in a Willys Wagon on a road trip from N. Cal. to Wash. St. It was knocking real good for the last 100 miles or so. I dropped the pan and it ended up being the first bearing I checked. I ordered one rod bearing from the NAPA and put it in. I kept that Wagon for 4 more years as a dailey driver and it never knocked again. The bearing material is much softer than the crank steel. If you find a bad bearing, check the crankshaft journal carefully to see if it has been damaged. If it looks good, just replace the bearing(s) and drive it. Also, check the bolt that holds the harmonic balancer (crankshaft pulley) to make sure its tight. I've heard that pulley make a knocking noise if it gets loose. Do yourself a favor and order a Factory Service Manual, if you don't have one. Do a search here and you will find out where you can get one. The fact that your knock seems to go away when you rev the engine is because you are increasing the oil pressure enough to cushion the knock. It comes back when the oil pressure drops at low RPMs. You may get other replies on this thread, so let us know how you are doing. Ask questions.

 

Sounds like a knock to me. Like I said its only when its warm, and at low rpm. I dont know much about engines so Im really hoping this is somthing I can fix.

 

I thought it might be a crank bearing. When I looked up the bearings it showed diffrent sizes. How do I know which ones to order?

 

If it's a rod bearing, it's not really a technical fix. You can check to see which rod it is by pulling a sparkplug wire and see if it goes away. If it does you know which rod it is. Also, if it doesn't go away it's not likely that it is a rod bearing. I'd pull the plug wires and clean the plug top and put a tiny bit of oil on it so the plug wire slips on and off easy. Then start the engine and pull the plug wires and see what happens. You could get zapped if you are a good ground, by the sparkplug wire with the engine running.

 

The old bearings will be stamped on the backs what their size is.

 

Thanks I'll give it a shot!

 

I agree with Patrick, I would check the timing chain, mine sounded the same. I guess I like to look at the simple thing prior looking replacing the bearing. I think iy will be far easier and cheaper to replace the timing chain than getting into replacing the bearings. you can look at the post of timing chain cover you will see just how worn mine was.

 

So I pulled the plug wires one by one, and the knock never changed. If its correct it has about 78k on the motor. I was thinking of doing the timing chain and gears, but my question is if you think this would cause the knock after its warmed up? normally the pressure reads about 20 when its at idle and warm. seems like this in a normal thing to change. Also while apart is there anything else I should do?

 

20 psi of oil pressure at warm idle sounds pretty good. That's where mine's at with about 30k miles on it. The timing chains are a known wear item with the Dauntless. It's possible that the chain is growing as it gets warm and that's why it doesn't knock when it's cold. Buy the best one you can find/afford. They're not that much fun to change either. I would much rather do rod bearings than a timing chain. Might be a good time to change out the water pump too.

 

Thanks guys! Im odering parts from Napa in the morning. R)