93 Grand Cherokee sounds like diesel

Strjock81 · Nov 30, 2004

We have a 93 Jeep Grand Cherokee with the 4.0L I6 in it, and have owned it since new. It has 175,000 miles on it, and other than trannies, have never had much trouble with it. It's just that the motor sounds like a diesel almost exactly when it is idling, and fairly loudly. The exhaust isn't the problem as it is all brand new and quiet. It has done this for quite some time, and continues running fine. Oil changes mostly done at quick lubes at 3,000 miles until about 140,000 miles. Uses about 1-1.5 qts, either due to leaking slightly or consumption in the motor. Have been using 15w-40 HDEOs now for quite a while because its generally what I have sitting around for my Cummins and farm tractors. Have tired an Auto RX cycle for 1500 miles, but didnt do the second one even tho I am over 100,000. Tried a couple other additives, nothing really seems to work. One time it puked oil back onto the air filter as well. (PCV?)

I don't know that much about gassers, so was hoping someone could shed some light on this for me.

36coupe · Nov 30, 2004

Could be a bad tank of gas,timing may be out of adjustment. How long before tune ups?

HEV · Dec 1, 2004

My 96 GC 4.0 has always sounded like a diesel. This has always been a common complaint with this motor, it sounds like a tractor. Even Consumers Reports identified this as a nuisance early on when the GC and Cherokee first used this motor. When Chrysler got the motor (after acquiring AMC) they added more material to the block to make it quieter (I believe they did this for MY 1996 when they made many other revisions). It helped, but they are still noisy. A thicker oil does quiet it down. The 4.0 loves HDEO 15W-40 oil. When I run M1 10W-30, the motor is clacketably louder. When I run a heavier 30 weight (think Amsoil or German Castrol), it’s much quieter. I have run Chevron Delo, Mobil Delvac 1300, and Schaeffer Series 7000, all 15W-40 HDEOs, and they all resulted in quieter operation.

Gary Allan · Dec 1, 2004

The thing has a very noisy valve train. My roller rockers quieted it down somewhat ..but it's still the loudest idling engine on the block.

It's built into the design ..you can't fix it other than having a quieter loud engine.

JeepZJ4.0 · Dec 1, 2004

quote:

Originally posted by Strjock81:
One time it puked oil back onto the air filter as well. (PCV?)

Something must be wrong if it does this. There is no PCV system on the 4.0L. It has a Continuous Crankshaft Ventilation. It's a different system.

Strjock81 · Dec 1, 2004

Well it was a little overfilled from a quicklube when it puked the oil on the air filter that time. I had forgotten about that. Well apparently this is a somewhat normal phenomenon for this engine. A lot of the noise is definitely valve train in nature, with a light knock under it. As I mentioned we ran the Auto RX until "disaster" struck. I bought a cheapo Super Tech filter at 750 miles to replace the Fram that was on there to make sure I was catching all the junk the RX was loosening up. I just swapped the filters, topped off oil and put in another couple ounces of RX. Started the Jeep and oil went everywhere. Something I'd never let happen had happened--gasket from old Fram had stuck to the housing and caused a bad seal with new filter. Lost most of the oil in the crankcase all over my shop floor!

So I filled it back up with CenPeCo 15w-40 and put some Napa Valve Kleen stuff (smelled like paint thinner kinda) in the oil and some Rislone (the add anytime) in it and some super duper heavy duty ultra extreme mighty fuel system cleaner in the fuel tank. Mostly I am just experimenting at this point in time to see what can be done since it has gotten really noisy over the last 30-40K miles. If I end up screwing something up with these products it's no big loss...

JeepZJ4.0 · Dec 2, 2004

My ZJ's 4.0L is alot quieter now that I am running Mobil 1 0w40. Even my father was impressed.

HEV · Dec 2, 2004

Check you CCV line at the back of the valve cover. It sounds like it is blocked. Just pull it off and clean it out.

T-Keith · Dec 2, 2004

Iron Dukes are also loud and some say sound like a Diesel. They also run forever, so I wouldn't worry about it.

Greaser · Dec 5, 2004

http://jeepsunlimited.com/forums/

JeepZJ4.0 · Dec 5, 2004

quote:

Originally posted by Greaser:
http://jeepsunlimited.com/forums/

X2!! I'm on there with the same user name.

Eddie · Dec 7, 2004

Seem to remember that the 4.0L engine used Plastic valve cover some years and changed to metal because of noise. My 4.0 engine had metal (1995) and was still making the sme noise at 247,000 miles on Mobil1 10w30

ddolat · Dec 7, 2004

The exhaust manifolds on these trucks are known for cracking at the welds, usually between the pipes where it would be hard to see unless you remove the manifold. On my old ZJ, I replaced the original manifold with the updated version available at the dealer. This new version has flex plates incorporated into the outboard pipes.

Gary Allan · Dec 7, 2004

quote:

quote:Originally posted by Strjock81:
One time it puked oil back onto the air filter as well. (PCV?)

Something must be wrong if it does this. There is no PCV system on the 4.0L. It has a Continuous Crankshaft Ventilation. It's a different system.

The CCV uses a metered orifice to induce the crankcase blowby vapors into the combustion stream. It's a fixed opening to a tube. The metering point is at the valve cover (at least on the 99 model year). A PCV valve is a regulated manifold leak (the fluttering valve). The CCV is a limited manifold leak.

If the puking out of the "innie" hose (where ever it is connected above the throttle body) you may be in luck and it's just the metered orifice being clogged.

These engines are very durable. You can lose a timing chain and nothing happens. It's not an interference engine. Most of those that complain of blowby are around 20 years old ..and are just turning the clock ..maybe one and a half times around. Those never saw much long mileage and perhaps sat idle for a few years.

Here's something for you to digest. This is one possibility that we haven't discussed yet. This is fairly rare. I've only heard of it happening twice. cam walking and bolts rubbing on the t-cover. Check your distributor gear

93 Grand Cherokee sounds like diesel

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