1999 Chrysler Sebring engine noise (2.5L V6)

[92saturnsl2]

This is what rolled into my driveway today-- offered to do some semi-charity work for a good guy at work that's down and out with this car. He put way too much money into it paying hack mechanics to do basically nothing but swap parts. The caveat being he has to deliver it to me and pick it up if it happens to be a complete basket case and can't be driven away. I don't know the full history, but when he first bought it, it ran rough especially when cold and had an obvious misfire, but otherwise was a decent running car. It's an 06/1999 build date Sebring convertible higher trim (LXi I think) w/ a 2.5L 6G73 Mitsubishi V6.

Fast forward to today, it has a loud top-end noise along with the same cold-running issues and misfire. If he'd have told me it was a diesel, I'd say it's sounding just fine.

Can anyone take a stab at what would cause this noise on this particular engine? Timing belt seems intact as I can view it from a missing cover. Also the ECU connects only to a very rudimentary OBD2 scan tool I have, but the only live data that seems accurate is engine RPM. No SES light either. It used to connect to my advanced scan tool (Launch X431) just fine before the hacks got ahold of it. Also the alternator is not charging despite being replaced twice by (probably) the same hacks.

Sad thing is, it's a beautiful car with no rust. If you have the patience to warm it up, it runs around just fine other than the misfire and diesel sound. I should mention that oil is full and recently changed, and pulling the oil fill cap reveals plenty of lubrication / splash on at least the front bank. Inside the valve cover looks very clean for 120K.

 

[dishdude]

Sounds like a cracked exhaust manifold.

 

[92saturnsl2]

Sounds like an exhaust gasket leak or cracked exhaust manifold.

Definitely something mechanical, not an exhaust leak.

 

[dishdude]

Definitely something mechanical, not an exhaust leak.

A cracked exhaust manifold can sound very mechanical.

 

[dumkid]

Loose timing belt tension (failed tensioner) or the lifters are known for ticking if they get dirty. You could probably stick a 3.0 or 3.5 Mitsubishi in it without much trouble. Run it with the timing belt covers off and see if the belt appears to flap around or if it stays tight. If it's a lifter noise (sounds like a Chevy) and the engine has good oil pressure, slowly rev to 3000 rpm over 15 seconds a few times (7-15 usually works) and see if the engine is quieter.

And a cracked exhaust manifold can make some awful noises but I doubt it would cause a misfire

Sometimes the coils or the ignition control module fail, and in a waste spark system this will turn your v6 into a very rough running 4 cylinder. All my experience is with my Mitsubishi Montero, the engine should be the same except for displacement but the wiring and other things will probably be different

 

[dishdude]

A misfire will blink the CEL. This engine is pretty basic with a distributor and ICM built into the ECM. Could the hacks have mixed the wires up? The voltage regulator is also built into the ECM, the fact that it won't connect to the scan tool is another clue.

 

[dumkid]

Not every car I've worked on has a misfire blink the cel, but a misfire will always set a cel (if it happens more than once or twice)

 

[92saturnsl2]

A misfire will blink the CEL. This engine is pretty basic with a distributor and ICM built into the ECM. Could the hacks have mixed the wires up? The voltage regulator is also built into the ECM, the fact that it won't connect to the scan tool is another clue.

I think there's some ECM issues here. The car won't charge and there's a huge orange sticker on the 2nd (or third?) new alternator the hacks put in that says "voltage regulation performed by ECM". The fact that my scan tool won't connect now, when it used to is a huge red flag. When he first bought the car I was able to diagnose an ABS code, random misfires, and such.

The top-end noise is very new though and I can't see how it would be related to ECM issues.

 

[dishdude]

I think there's some ECM issues here. The car won't charge and there's a huge orange sticker on the 2nd (or third?) new alternator the hacks put in that says "voltage regulation performed by ECM". The fact that my scan tool won't connect now, when it used to is a huge red flag. When he first bought the car I was able to diagnose an ABS code, random misfires, and such.

The fact that a hack was in there is concerning, I think a wiring harness may have been damaged which is causing the ECM issues.

 

[cptbarkey]

I would look for an exhaust leak first, compromised gasket at the head.

 

[wag123]

I don't hear a characteristic exhaust manifold leak.
This engine was notorious for soft cams and would wipe the cam lobes. That is what it sounds like to me. This is also going to cause cold-running issues and misfires.
My advice? Punt.

 

[TheLawnRanger]

It's almost 25 years old.

 

[Niker]

Not to many left on the road due to the timing belt and interference motor design. Most of the ones I've seen at the boneyards have high mileage, pretty reliable drivetrains, except the timing belts never got proactively changed.

Put together a 2000 Sebring JX into running order a few years back had 75k, now sitting at 145k. It originally sounded much like the one in your vid when I first got it. Also was rough idling and throwing a misfire code.

Found out it was the ignition coil, which is built into the distributer. A guy by name of syyenergy7 on YouTube has an old vid showing where the coil is in the distributer, believe it's a UF-302. The coil is usually close to the price of a Cardone distributer so opted to go that route instead. As syyenergy7 points out in the vid, check the distributor cap for the small inner spring-loaded contact. Mine was also rattling around in the box. After distributer replacement, the misfire went away and check engine light has stayed off. Diesel sound mostly went away but could still be heard slightly.

The diesel noise was fully eliminated when I changed the EGR valve, couldn't find newer OEM unit so used the AutoZone EGR380 unit. Upon replacing I found the EGR tube to be mostly clogged, along with the port in the upper intake manifold. Also the gaskets at each end of the EGR tube were crumbled and powdery. So probably a source of vacuum leak. First AutoZone unit lasted 6 months, second unit has been going about 2.5 years so far. AutoZone has lifetime replacement. EGR tube has small 9 or 10mm bolts that hold it on, kind of pain, definitely recommend swivel extensions.

Does your alternator have any oil staining? The alternator had previously been replaced twice prior to me taking ownership. The cam seals on the 2.5L leak at this age, of course the alternator is directly below the oil drip path when the seals go. Not sure exactly what happens in the alternator, something shorts out. Previous owner stated that at last alternator change, day before, the car's headlights and interior lights would cycle from extremely bright to very dim. Sounds like a voltage regulator getting fried? If replacing the cam seals isn't practical, you can take a flat sheet of aluminum and fabricate a drip guard over the half of the alternator that faces towards the cam. This will spare the alternator from getting soaked in oil. I believe O'Reilly's, at one point in time, sold an alternator with such a guard already in place for the Mitsubishi 6g engine family. I can share a picture of the guard I made later. The original cam seals are a bear, or sometimes downright impossible, to remove but they do not need to come out to fix a leak. They can actually be driven further into the engine and new ones installed over them.

Other than that, I would pull the inspection covers to check the timing belt. Once the belt lets loose, the engine is toast. Though pulling the covers is a pain, since the upper intake manifold, side engine mount, and two serpentine belts need to come off from what I recall. Once you do get the covers off, I recommend cutting small rectangular holes in each, to create small inspection windows so you don't have to repeat this exercise.

Best of luck