[6869FB]

2003 Neon, 160,000 mi 5 speed manual, 2.0 SOHC.
Started to work yesterday morning and heard something bang or snap. Then a vibration and a related noise started somewhere in the front. Turned around, got it home and took my old van to work. Looked at the Neon last night when I got home; removed the front wheels, looked at the brakes, driveshafts, suspension, etc and didn't see anything out of the ordinary. I held the engine at 3000 rpms in neutral and it seems to be running fine so I don't think it's the engine. Drove out of the garage and started down the driveway and the vibration or mechanical contact is still there even when moving at slow speeds (5 mph) It might be happening only when the engine is under load but I didn't want to venture out onto the street and not be able to get it back.
Anyone have any ideas on what it might be? Clutch, trans?

 

[ImperialCrown]

Do you think that the 'snap' was felt in the floor or the steering wheel?
Left or right side?
Possibly a motor or transaxle mount let go and engine vibration is now being transmitted 'metal-to-metal' into the body?

 

[6869FB]

Do you think that the 'snap' was felt in the floor or the steering wheel?
Left or right side?
Possibly a motor or transaxle mount let go and engine vibration is now being transmitted 'metal-to-metal' into the body?

I hoping it is just a motor mount. I don't think the "snap" was in the steering. Seemed more drivetrain related.
I was thinking of getting my son to come over and then he or I observing the motor as the clutch is gently engaged with the hood open, maybe with the brake on. Hopefully i can spend more time with it tomorrow.

 

[dana44]

Do a little safety check first by jacking the car up, putting the front wheels blocked off the ground, and start with the transmission in neutral, rotate one wheel at a time by hand. If nothing is felt this way, then start the engine and gently let the clutch out, see if you can locate a problem that way. Another thing you may want to check is rocking the engine back and forth with engine off, see if your son can see anything move in the event you can't make it clunk. Did you verify it isn't a wheel itself? I had a bubble on the tread that I looked for three different times before I happened to find it.

 

[6869FB]

I took it up the street a few days ago. After I got up to about 20-25mph, I put it in neutral and coasted with the engine off. I don't remember if I had the clutch in or not. Anyway, there was no vibration, only silence. Unfortunately, I tried to start it while it was still rolling. The engine immediately died. I rolled into someone's drive and tried repeatedly to start it but it would immediately die. I called a friend and we towed it almost 1/2 mile and got it home. While I was waiting, I hooked the scanner up and the code was P1681, no fuel level bus. No matter cause I waited a couple hours and it started right up.
Since then I put in new Champion plugs and replaced the sp plug tubes and seals with new ones.(there was oil at the bottom of 2 of them) I let the sealer set up for 24 hrs before starting it. I took it out but backed right up again before I hit the end of the drive. The vibration was still there. I did a compression check this morning and all 4 cylinders are 159-162 psi on a cold engine. With the front tires off the ground, I started it, put it in gear, and revved the engine a few times to see if it looked like the engine rocked excessively. It did not. I took a real close look at the 4 engine mounts/ struts anyway. The upper and lower strut rubber shows cracking but not all the way through. I even removed the trans mount on the driver side and it looks perfect so I don't think the mounts are the problem. I spun the tire manually and there is no noise when in neutral. Doing the same with the trans in gear I can hear a rattling as it rotates. Having never done that before I don't know that is normal.
There are no codes and engine light is off. So I'm coming up with these possibilities:
1. Bad fuel injector. (Don't know if that would turn the engine light on and I dont know how to check other than substituting a good one.)
2. Fuel pump
3. Something in the drive train, clutch or trans.
I can fix anything that is wrong, just need to figure out what it is.

 

[dana44]

By just coasting and not feeling the vibration alleviates the axles, but it doesn't narrow the problem enough. Get her back up to 25-30mph and simply push the clutch in and see how the vibration changes and whether the engine is running rough still. Does she idle and rev smoothly or does she cut out? If smooth, then it would be in the transaxle.

 

[6869FB]

Since my last post I removed the injectors and had them professionally cleaned and tested. All 4 flow within 0.8% of each other. The car sat for 2 weeks and yesterday at startup with the clean injectors, there was a knocking inside the engine. I could hear it most clearly down low on the exhaust side of the block. It definitely was internal and not valve train. It diminished as the car warmed up. Sitting still, in neutral, not moving, there definitely is a vibration until 2500-3000 rpms then it smoothes out. Last time I drove it, same thing, no vibes after 3000 rpms. Just idling it doesn't seem to be too bad but this engine never ran very well at low rpms since I got it with 74k. Anyone got anything?

 

[ImperialCrown]

Is the low-speed vibration possibly a cylinder misfire? You stated that the car never performed very well at lower RPM. Leaky valves can cause this. It would be worst at idle.
A static compression 'leak down' test is better than a cranking compression test for diagnosing this. Air heard escaping from either the tailpipe or throttle body would indicate a leaky valve. Air heard escaping from the oil filler cap (crankcase) would indicate bad rings or piston.
I simply attach a compressed air hose to a fitting that screws into the spark plug hole. All 4 valves for that cylinder need to be closed for the test. A leaky valve (or rings) will be less noticeable as the engine speed is increased.
The tapping noise could be valve related and may possibly be related to a misfire. Some 2.0L engines did have a piston wrist pin tapping noise that got better as the engine warmed.
This is beginning to sound like an internal engine mechanical issue.

 

[6869FB]

Is the low-speed vibration possibly a cylinder misfire? You stated that the car never performed very well at lower RPM. Leaky valves can cause this. It would be worst at idle.
A static compression 'leak down' test is better than a cranking compression test for diagnosing this. Air heard escaping from either the tailpipe or throttle body would indicate a leaky valve. Air heard escaping from the oil filler cap (crankcase) would indicate bad rings or piston.
I simply attach a compressed air hose to a fitting that screws into the spark plug hole. All 4 valves for that cylinder need to be closed for the test. A leaky valve (or rings) will be less noticeable as the engine speed is increased.
The tapping noise could be valve related and may possibly be related to a misfire. Some 2.0L engines did have a piston wrist pin tapping noise that got better as the engine warmed.
This is beginning to sound like an internal engine mechanical issue.

Just wanted to update this, sorry I waited so long. Even though the spark plug wires checked out OK with an ohm meter, I replaced them and it was an instant fix. It really seemed to miss the most on deceleration which was confusing. The coil terminals were "dirty" so I used a scotchbrite pad to clean them and used di-electric grease at the plugs and coils. This may have been a contributing factor. Car just passed 200K and running the best since I've had it. Thanks for the responses.