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'92 Plymouth Voyager 2.5 4cyl top-end noise / pre-ignition?

I recently completed an engine rebuild on a 2.5 4cylinder engine in the above vehicle. I did the rebuild because the engine was burning about a quart every 40 miles and had no oil pressure. Also, it had a lot of what sounded like lifter noise.. a real racket, it drowned out the radio at highway speeds.. Which I attributed to the lack of oil pressure. This is an overhead cam engine.

After the rebuild, the engine has great oil pressure.. lots of power, everthing is great. Except, there is still significant top end noise when idling and a lot of what sounds like pre-ignition while driving. It is possible that what I am thinking is top-end noise is actually pre-ignition when idling. The vehicle is timed (12degrees) and runs like a champ.. It just sounds like a diesel. The knocking disappears when accelerating, and becomes very pronounced when decelerating.

At first, I thought that perhaps the oil-channels in the block were not allowing significant oil pressure to the top end.. Blocked, maybe. But I don't see why the oil pressure should change on deceleration or acceleration, the crankshaft is still rotating at roughly the same speed, so should be about the same oil pressure... I'm settling on this being an ignition problem, but there aren't that many ignition parts in the vehicle. Does anyone have any thoughts?

Thanks,

-Adam

Reply to
Adam Jacobs
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Piston pin knock. The 2.2 and 2.5 litre engines with original pistons are prone to it. The engine carries on running normally, but eventually it gets so loud that the engine does sound like a diesel. If you'd fix it, install new pistons.

DS

Reply to
Daniel J. Stern

Reply to
Adam Jacobs

Well...that sort of depends on your priorities. As the piston pin bores get more and more wallowed out, the pounding effect becomes greater and greater and the wear accelerates. Eventually you'll break something, probably a piston, and then bad stuff'll happen (e.g. rod through the block), and then all your rebuild work will go "ker-flush". Also, the noise will keep getting louder and louder, which will not only remind you every time you drive the van that something's wrong, but will also make the van impossible to sell, if you were ever inclined to do so.

Reply to
Daniel J. Stern

Oh. How many miles / months do I have? I don't think I can afford to tear it back down inside the next 6 months.

Reply to
Adam Jacobs

I don't think your engine will grenade inside the next six months, but take it easy.

Reply to
Daniel J. Stern

Reply to
Adam Jacobs

When you say rebuild what exactly did the rebuild consist of? If you suspect it to be a wrist pin noise or lower end bearing noise take each plug wire off one at a time to see if the noise goes away. take one off put it back on and take another one off until all 4 were isolated.

Glenn Beasley Chrysler Tech

Reply to
maxpower

Thanks, I'll have a look. I replaced the head with a new cast, including valves/springs/cam etc.. rings, rod bearings. I didn't pull the engine, so the main bearings didn't get done.. and the cylinder ridge didn't look bad, so I honed them and reinstalled the original pistons. One of the connecting rods was bent, so that got replaced, along with the intermediate shaft (which was missing a couple teeth) and the oil pump & screen.

Reply to
Adam Jacobs

It looks to me that what I'm describing is Piston slap. I noticed some odd markings on the sides of the cylinders when I pulled the pistons.. But as the esteemed Nomen Nescio points out, I'm an idiot, and didn't think of the implications.. I just honed it and tossed in the old pistons. What causes this? If I bore the cylinders out and put in pistons to match (along with the main bearings that I neglected) will I be in the clear? It seems that in the end, this will cost what a mexican rebuild would have.

Reply to
Adam Jacobs

Ring ridge is a thing of the past, if you notice I bet you still see the cylinder hone marks in each cylinder. What you are probably hearing is wrist pin noise. That was a common problem on that engine.

Glenn Beasley Chrysler Tech

Reply to
maxpower

Pretty sure it's Piston slap. I checked the discarded piston&rod and there was no noticeable play in the wrist pin. However, after about 3 days of driving there is plenty of fine metal dust in the oil pan and the hone marks are worn on each side of the cylinders. Also, the piston that was replaced is worn smooth on the sides as well. The really odd thing (to me.. I know very little about these engines) is that the top of the cylinder was round and I have very good compression in each engine. I read something that said that these engines are basically stroked 2.2's and the piston skirt extends beyond the bottom of the cylinder well.. So I suppose the bottom of the cylinder could be ovalled enough to cause slap while still having good compression.

Reply to
Adam Jacobs

Just ignore No-Man - if you bothered to google some of his past posts you will see he's a friggin ijiot.

Ted

Reply to
Ted Mittelstaedt

And how exactly does this incomplete rebuild differ at all from a worn engine that hasn't yet blown up but is about 5,000 miles away from doing so? There's plenty of those running around on the roads.

Ted

Reply to
Ted Mittelstaedt

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