I am having some trouble out of my car as of late and wanted to see if anyone could help diagnose it for me. I started having a miss a couple weeks ago and it started off small but eventually got worse. On top of the miss, the car would occasionally cut out and die completely when driving, however it never quit on the interstate, usually it was when I was cruising at 40-50. My car starts easily after it has been sitting a little while but after it would cut out and die the key would not start it so I would have to dump the clutch to start it quickly so I could keep driving. The car quitting doesn't seem to be linked to speed because it also quit on me when I pulled into a parking lot and put it in reverse to back into a parking spot. After a lot of cranking, it finally started but it definitely didn't want to. Also, the miss seems to be the worst at lower RPM's and smoothed out pretty well the higher I would go although it still had the occasional sputter. The miss isn't always terrible, sometimes it felt very minor, but when it was terrible it would jerk the whole car pretty violently and either quit or eventually smooth out. I pulled the codes and it reported both of my O2 sensors were bad and the coolant temp sensor was stuck open. I replaced the O2's but have yet to replace the coolant temp sensor because a bigger problem has surfaced. Note that the O2's seemed to help the miss a lot at first because the car no longer quit on itself but a couple days afterward the problem went back to the same. Also note that the engine light is not coming on anymore; it was coming on while driving and was pretty closely related to the car dying. The miss was always present with the engine light off, but it did seem to get worse after it came on.

So now...the bigger problem (maybe). A couple days ago I was driving to work and began hearing a new (and bad) noise coming from the engine and also the miss/violent shaking was noticeably worse than usual. I went ahead and finished the drive to work and let it sit and think about what it had done ..Anyway, after work the noise seemed worse so I pulled over to investigate because it sounded like something was going to break. I can't really hear the noise at idle, but when I give it some gas, there is a loud clicking/humming/strange noise coming from the motor. Hoping that it was just a rocker arm coming loose, I took off the passenger side valve cover to listen more closely as that sounded like where it was coming from, but unfortunately it was not a rocker arm. It sounds like it is coming from the intake/under the intake. Also, unfortunately, I had my car on a lift with it running and could hear the noise through the exhaust, at least it seemed like it was coming through the exhaust but it could have just been the motor noise, not 100% sure on that.

The oil pressure didn't seem any lower than usual, and also the oil was changed a couple weeks ago and is still at the top of the fill line. I'm not good at diagnosing deep engine problems like this, but my brother suggested it could be a collapsed lifter but that may be wishful thinking. I don't think it is a spun bearing or anything because the click/noise in general is not that loud, and also it is extremely faint at idle which doesn't quite add up with what I have seen/heard on videos. I took my CAI off from the throttle body to see if I could hear the noise come through the TB any louder, but it did not. I also took the belt off and started it but there was no change in the noise.

Sorry to type so much but I wanted to give a lot of detail, but if there is additional info you need I can provide it quickly.

Thanks in advance for ANY help or direction you can give. This car has been my baby the last five years and is also my DD so I need to get her back on the road ASAP!


Excuse the dirt
Video: http://www.youtube.com/watch?v=WYMux...ature=youtu.be

 

if you are hearing noises thru the intake and exhaust it sounds like a valvetrain issue........can you take a video of the noise? also how many miles on the car? any smoke out the exhaust?

 

Perhaps an oil change (dirty oil) and inspecting the oil during this process first. Check exhaust to make sure u dont have any leaks. What was the last job done to your Z28?

 

No smoke, but it does run/smell very rich. Unfortunately I'm at work so I can't take a video right now but I will later this evening.

Car has about 138,000 miles on it but I have legitimately babied that car the last 2 1/2-3 years or so. I got it with about 80,000 on it 5 years ago and was 18 at the time so I drove it kind of stupid then but I grew out of that and rarely even get on it anymore and keep up on the maintenance well. Maybe I should have been driving it harder

 

honestly i was at first wondering whether the opti was comming apart but that doesn't explain the noises from inside the motor......kinda need a video its hard to tell via explination lol

 

I change the oil every 2500 miles and just changed it two weeks ago today so I don't think the oil has anything to do with it. I have examined the oil on the dipstick and don't see any metal shavings or anything. Looks like fresh, clean oil.

And what exactly do you mean by job? Oil change and O2 sensors are the only thing I've done recently. I have not had any trouble otherwise for a long time so I have just been changing the oil and driving it. Last significant upgrade was back in March when I got a mail order tune.

 

I understand I had to replace the opti last summer (2010). I used a Delphi replacement. When the opti was going out it backfired horridly and really cut out in high RPM's so I don't suspect the opti (not yet anyway).

 

im starting to think potentially a lifter that went bad that could explain the noise and possibly a slight misfire but that wont make the car stall and shut off.........you didn't over-rev it did you?

 

In many cases on cars that I work on, the problems almost always can be traced back to the previous job that created the problem. Not always though. Example: Working on LT1 right now that was surging/idling bad that recently had rockers and springs installed from his buddy (He was being too cheap to pay me $150 for springs and rockers install). Many of the rockers were not lashed correctly...too tight! It's now fixed and runs really good... For your Camaro though, it's tuff to pin-point this issue without looking/hearing. Inspect your belt tensioner and pulley area for anything. Perhaps we can get lucky...

 

No, the highest I have went since the misfire started was probably ~3500 RPM just so I could see if the misfire continued in higher RPM. Before that, like I said, it was babied so even if I went on a fast drive I still shifted conservatively around 4000-4200 RPM.

 

I wish I had something to link it to but I haven't had to go into the motor to replace anything at all so this is the first time I've had an apparent internal motor problem.

 

The noise seems to be around #6 or 8. Whatever happened to his suddenly happened to mine also. It was fine on my way home and got really bad really quick. It would barely start and was running extremely rich. Then I went to start it and CLUNK. Now I can only turn the harmonic balancer about 1/8 of a turn tops... I believe mine is dead.

 

I would honestly start with the Coolant sensor. Mine went bad and caused hell for my car that seemed very similar to what you are going through. it's a super easy fix and it's cheap. also check for carbon around your manifold gasket. when my CTS went the motor shook so bad that it sheared 2 manifold bolts out of the head and a slight leak from the manifold can be mistaken for a valve noise.

 

Videos are posted! Sorry for the delay. The first one ended because the car died on me though I'm not sure why.

I replaced the coolant temp sensor today but couldn't really troubleshoot if it fixed the miss or anything but due to the car quitting on me then I'd say not. Oh well..just need to get the noise fixed first.

 

Remove the belt and Next you got to listen to the water pump and make sure it's not the water pump bearing. If you can rule that out then I would say it's time to move on to looking internally.If the water pump bearing is going bad it could be leaking so look for coolant around where the drive conects and on top of the opti. It could be leaking coolant onto and into the opti causeing the miss.

 

The belt is already off. I was hoping it was the alternator or something but unfortunately the noise is definitely coming from the back of the motor.

 

I would do a leakdown test on the motor...compression test. Sounds to me like u could have a bad valve, lifter or ring that could cause the miss and the noises.

 

Better video is posted. Some were having problems distinguishing the noise so hopefully the new one will be of some help.

 

Pull the inspection cover off your transmission and see if there's anything in there. I had a flexplate bolt fall out once that sounded just like a spun main bearing.

 

If it's out back maybe it the throw out bearing. Try engaging the clutch and see if the sound changes, or have you done that already too?