So after driving my truck for about a week after replacing timing chain and quids truck ran very good. Then the other day I was at a light and truck shut off I thought maybe because of bad alternator so had a jump start truck turned on then engine started shaking like it was about to shut off. So I gave it gas and drove it down the road to my house when while I was driving it would not gain power then I parked it and it just sound like it wanted to shut off engine shaking and I noticed a rattle noice. So long story short found out it was a loose chain fixed the problem and cranked it up today and it starts ok but then it will go hight on the rpms and then drop down to about 1000rpms and then once it gets lower than 1000rpms it starts to shake and it will shut down or it corrects itself and sounds ok back and forth. But when I give it gas it gains power but I can hear like a sound I can't explain like if I had a hole in the exhaust or something. I know I have a bad alternator but could that really be the problem which I wish it was but my light work fine but I want to look at the easier stuff before going with the more critical things please help!!!

 

Compression test on all 6 cylinders will tell the tale if valve crank timing has slipped, and in the 4.0l SOHC one cam can slip and not the other so compression on 1 bank can be higher than the other so low power and shaking

Low voltage can cause engine running problems, so yes failed alternator means engine is running from battery voltage only which gets less and less the longer the engine electrical system is sucking voltage from it

4.0l SOHC runs 9.7:1 compression ratio, so expect 165-170psi from each cylinder, new engine would be 175psi, with good battery, crank speed is important, drained battery gives slower crank speed RPMs
If battery is between 12.4v-12.8volts then that will be good crank speed RPMs

 

Thanks for the info but I discovered a critical failure after I tried and thought I fixed the loose chain problem and went to crank the truck up again it sounded very rough spitting and sputtering and herd the rattle again and noticed I had a small hole in it???so this time I decided to remove the valve cover on passenger side and well let's just say all I seen was the timing chain sprocket and didn't see the chain on it so I was like well there is the problem chain must of broke. But what could have caused that to happen? everything was brand new!! But I'm just going to wait and try to purchase another engine this one already has 245000 and I'm so tired of messing with it.

 

Factory defect most likely, it does happen

Well the tensioners are new so save them to install on the used engine you get

 

Ok thanks I'm going to try to purchase a reconditioned one any thought on those?

 

No, not really since I never used one

The warranty usually isn't worth much especially for DIY installs, "they" will always claim "installation error" if engine fails, hard to prove otherwise since you are not a professional mechanic, and they have a good point, "they" don't know if you ran it without oil or any other abuse, before calling and try to get another engine

If you have a shop buy and install a rebuilt engine then they have to deal with warranty, and are more likely to get a new engine and you are just out the down time, but 2 or 3 times the price of DIY

A rebuilt engine is what it is, read reviews of other engines they may have sold, RECENT reviews

 

It's either that one or the local junkyard that has pretty much all newer cara. They have a engine that came off a 04 ranger Wich is 1year newer than mine but they just can't give me the mileage since it's 10 years or older. But it is a local shop and they said it's been tested before it goes on the shelf plus they give me 6month warrant Wich the reconditioned motor only gives me 90 days. I think the used 6month warranty motor sounds better because it's local shop and it's 6month warranty and the reconditioned one is about 2 hours away so there is the convince factor and more warranty. What do you think?

 

And I just seen your message on the warranty hopefully that's not the case for me and it goes smooth enough

 

Previously tested engines(used) can be fine, if its from a wrecked vehicle as least you know it was road worthy at the time of the crash, vehicles with bad engines rarely get into accidents, lol, but not never.
Mileage would have been written on the tag if it was low, so assume high miles

Mazda B4000 2001-2010 used same 4.0l SOHC
as did 2005–2010 Ford Mustang, Mustangs used different CAMs for more HP but less torque
and 1997-2010 Explorer/Mountaineer

You will have to swap over most of your bolt on parts to any different year engine so don't limit you searches to Rangers when looking at used engines

 

10 4 I quess I'll do some more research on local yards with lower miles and decent warranty because I know even if the yard covers another engine it won't cover my blood sweat and tears on pulling and installing engines lol