Hi all.

'07 i5 3.7 engine, about 165,000 miles on it. Has run very well, no codes. Uses no oil.
Today I was driving home through a 35 mph zone, coasting. Went to speed up in a 45 mph zone (very light on the accelerator), and the engine didn't seem right, and almost immediately I heard what I can best describe as a deep ratchet noise, from where I thought was the right wheel (to be clear, I now know it wasn't coming from the wheel, but that's the general area I thought I heard it from ). I also started to smell something burning. Got off the gas and coasted, very very very worried I was going to start on fire (thankfully I didn't). Engine idled during this time, but wasn't right (but not really that bad). Turned into a side street, and pressed the gas lightly. Noise came back. Seemed to only come when the engine was under a little bit of a load (from driving). I couldn't replicate the noise I initially heard while I was on the side of the road in park. Again, to be clear, this is NOT coming from the wheel, and is for sure engine related.

Engine does not idle correctly, but it's not all that bad. Hard to describe. While parked and pressing very lightly on the accelerator, I got what I think was a backfire through the intake.

NO engine codes. I can't believe that part.

Towed it home, and need to dig in. I'm very afraid that it could be timing chain related, but if I skipped a tooth, I can't believe the engine would hardly idle. As it is, you might not even notice the idle if you weren't looking for it. Also, I *believe* these are interference engines? Because of this I did VERY little running after the incident. I'm hoping that since it runs, I didn't hit valves? Perhaps the burning smell was from very incomplete combustion caused from bad valve timing? Also, I had my scan tool, and during the very few and short times I idled the engine, I did notice the O2 curves were both high (.8, .9), and constant. The sensor from before the CAT was not fluctuating like it should be (.3 - .7)

I'm going to start tomorrow by pulling the cam position solenoid, as this would be easy. Not sure if that would cause what I'm seeing here though. I'll look for dirty/missing screens, but outside of that not sure what else I could look for on that. I had planned on replacing it, but I'm very worried that I'm going to really wreck something when I go to test run it, if the problem is not the solenoid. I'd very much like someone to weigh in on the possibility that my problem is the solenoid.

Do you think my assumptions from above are correct, or at least justified? I'm new to this engine and don't know a lot of details, but I am somewhat familiar with engines. I'm really not looking forward to tearing into this engine, but it looks like I'm going to have to.

 

remove your belt and see if the noise persists. but it not running right might lean t'words timing chain issue

 

As always the big three:
Air
Spark
Fuel

I'd personally begin with a full visual inspection. Follow this up with a stethoscope and engine listening. You could tried a long screw driver for listening as well.

 

I sincerely appreciate the responses. However, I am very worried that I'll do more extreme damage if I run it more (if I already haven't)

I think right now is like to confirm a few things :

• Is the i5 3.7 an interference engine?
• Would this engine run at all, let alone decent, if a cam sprocket jumped a tooth?
• If this is an interference engine, would the valves hit pistons if the timing chain jumped only one tooth?

My plan right now is to tear into it this morning, starting with the cam position solenoid (only because it's easy). I'd like to even change it and see if it helps, but again, I'm very worried about more damage. So if anyone can confirm that a cam position solenoid, no matter how screwed up, would never cause the valve timing to go so bad as to cause backfiring, I won't even try then.

Thanks all again.

 

HH, was thinking of your post while driving to the truck.

Do thses coils go bad? Any possible way to check them short of replacing?

Could it be a fuel injector? Do they ever stick open? Too lean on a cylinder? Again, any way to check?

 

Yes coil on plug packs die just like any man made electrical part, they have a service life. Usually one dies and you immediately get a CEL with a noticeable miss.

The Atlas motors use VVT instead of EGR and if the Camshaft actuator solenoid goes, you can get a rough idle, no start crank, and almost always a CEL pretty quick.

The timing chain can stretch and theoretically skip a tooth if the timing chain tensioners are worn out, but you should have heard plenty of cold start clatter before that should happen. I would expect a broken valve spring before I would start talking about the timing chain skipping a tooth.

Have you pulled the oil dipstick to check oil level and quality?

 

Hey Doc and others,

Thank you very much for the replies. I have an update, and I think it's good news.

I took the coils out, and number 3 spark plug came out with the coil. It had blown out of the engine, taking the treads out in the process.

I now have a spark plug thread repair on my hands, and I COULD NOT be happier that I have the i5!. I have been looking at the spark plug thread repair kits, and found one I think I like:
https://www.autozone.com/test-scan-a...E&gclsrc=aw.ds

I like this one because it has the original threads to help guide the start of the cut.

My only hang up is the chips and how to get them out of the cylinder. I have read everything from "they all stick to the oil on the tap; they don't fall in the bore" to "stuff a long narrow cut section of rag into the cylinder and soak in oil, then pull out when you're done." Blowing the cylinder out with compressed air lays somewhere in the middle of the suggestions.

If anyone does have any tips for this job I would really appreciate it. Thank you all to have responded. I didn't get any sleep last night thinking I had a three day job on my hands, but now feeling a bit better because I at least have a path forward.

BTW, all spark plugs are going to be replaced, but I only plan on replacing the one coil, unless the general consensus is to replace those in sets as well ($$$).

Thanks again!

 

I highly doubt any spark plug "had blown out of the engine." Likely a prior owner F'ed that up and halfazzed it leaving the repair for later. Vibration over time got to it.

Use a shop vac with a small piece of clear plastic hose taped to the vacuum end, long enough that there is no way it could fall in the cylinder, and run that all around in there after the tap. Before you put in the new plug, do a compression test of at least that cylinder.

Good luck.

 

x2 with Doc, Don't leave any debris in the cylinder! Did you try to thread in a new plug torque to 13 lb ft? If you need to tap, my go to was a shop vac and disable engine starting+crank the engine without the spark plug. Also use a borescope to make sure all clear.

 

Conclusion .

I made the repair using the tool linked above. I used a heavy gear oil on the tap to attempt to stick the majority of the chips to the tap, but in reality a lot of chips remained in the cylinder.

I used a shop vac with an aluminum tube taped to the hose to get out the chips I could see. I thought I had all of them, but then blew compressed air into the cylinder (making sure the valves were closed), and got a TON more chips. I then taped a small hose to my compressed air valve, and spent about an hour blowing air around in the cylinder. I managed to get a few more pieces out.

Finall, I stuffed a long cut section of cloth in the cylinder, turned the engine by hand until the cloth was slightly compressed, and then pulled the cloth out. I didn't get any chips that time.

Truck runs great, and after thinking all night what I was in for today, was rather glad what it ended up being.

Thanks all who lent some knowledge!