Second Opinion

[Ghostcloak]

I have a 1993 MX-3 RS 1.6L I-4. I want a second opinion before I just start tearing open this car and replacing all the "what I think it might be" parts.

Yesterday the car ran fine. Today, I go to start the car and there is some SERIOUS knocking under the hood. I didn't let the car run more than 3 seconds the first time. I checked the oil thinking maybe it's low for some reason (maybe I lost a lot of oil before I parked it since I know it has a slight leak, I don't know). It was fine, resting just a hair below the full line as usual. I just changed the oil last month. No puddles of oil on the ground below. Just the typical dirt/oil residue on the bottom of the transmission casing from a slow leak somewhere. I have my wife start the car a second time while I look under the hood. It runs for about 10 seconds, the car sounds horrible and the knocking is extremely loud. I was unable to pinpoint it to one spot. Engine coolant expansion tank is full, the level hasn't budged from the full line since last year when I flushed it. Timing belt/water pump/tensioner all replaced a year and a half ago as well.

With that said, what are my options as far as what could be wrong? I'm thinking oil pump failure? Anything else I should look into that is easy to check out before I start dissecting the car?

Thanks

[Inodoro Pereyra]

Ok, first of all, don't worry about the timing belt. If it had snapped, the engine wouldn't run.
Before starting the teardown, there are a few things you can do:

Take a flashlight, and THOROUGHLY inspect the passenger side end of the engine. What you're looking for is anything that may be touching the belts, or one of the pulleys.

If nothing touches, take off the belts, one by one, and start the car after each one.
The first belt drives the A/C compressor and power steering pump. Take it off, and start the car. If the noise is gone, you have a problem on either the A/C compressor or the P/S pump.
If the noise persists, turn the engine off and get rid of the second belt. Start the engine again (remember now you don't have a water pump, so don't keep it running for long). If the noise stops, it's either the alty or the WP (my money is on the WP).
Turn the engine off, and turn the alty and WP by hand. If either of them "clicks" or shows signs of a less than smooth operation, take them off and get them tested (the alty) or replaced (the WP).

If the noise persists with no belts, get ready for a long day...

[umcamara]

Do you have an engine malfunction light?

[Ghostcloak]

come to thing of it... If I compression test it, that should tell me if a lifter is bad right? What should the compression numbers be on an B6-ME?

^^ I'll give it a shot... Thanks... It's definitely a knocking noise, but who knows, could be a water pump or alternator...

^ I'm 95% sure the CEL didn't come on... But I'll go back and see...

[Redline322]

Sounds like the lifters picked up a piece of dirt, get some seafoam or other sort of engine detergent to clean it out. GM dealers sell some called EOS I believe and it works really well too. If you are running thick oil like 10W30 or thicker, try switching to 5W30 too.

[Ghostcloak]

Well.. No CEL. The car vibrates a little too when the engine is on. I'm going to take off the valve cover and go from there. None of the accessories are making the noise. I've spotted the oil leak coming from somewhere above the AC Compressor on the block, if that's any help.

Of course, there's that one stuck, stripped bolt too that you can't get off... ALWAYS....

[Ghostcloak]

Could it be the HLA issue you guys have mentioned? The oil has been changed regularly every 3k-4k miles with Castrol Syntec 5W30. After taking off the valve cover and inspecting the rockers and springs, nothing seems out of place (and the metal is gold in color, showing good wear/maintenance). The car does generally sit over the weekend, but is a DD from M-F.

I haven't let the car run more than 10 seconds because I'm afraid of making the situation worse or ruining the engine.

[Inodoro Pereyra]

If the problem is the HLAs you'd hear a tapping noise that, while bothersome, is not really that loud. It would sound kinda like you tapping on the valve cover with a wrench.

If what you hear is a loud bumping sound, it can be something...well... worse.
Check the oil for metal shavings. Take a can opener, open the oil filter and check the paper element. If you have shiny flakes on it you may have spun a bearing...

[Ghostcloak]

Okay. So here's the test from today's compression reading, while standing in front of the car from left to right (or passenger's side to driver's side). The fuel injectors were disconnected, TB 100% open, and all the plugs were removed prior to testing.

Initially:
120psi
75psi
50psi
50psi

Then, after squirting a little bit of oil in each of the plug holes:
170psi
130psi
125psi
125psi

From what I've calculated, my compression numbers should be ~120psi, correct? (7.8:1 compression ratio x 14.7psi = 115psi)

When I started the engine up, the "ticking/tapping" definitely quieted down. The tapping was not present when I was doing the compression testing. I started the car, which smoked a little given the oil I squirted in each cylinder. Then it dissipated. After about 1 minute of idling, the car sounded QUIETER than the past year I've had it (all the ticking/tapping noises about 90% gone!). I drove the car around, which ended up being fine. Everything seemed to work itself out. I'm leery though because I know everything can't possibly be fine. Something happened. I had the car looked over by a guy who has built a couple engines and he says the head probably needs to be rebuilt (new rings, seals, HLA's, get everything redone to increase reliability and maybe even gain a little HP ). It could be my rings causing loss of compression and detonating and squirting a little bit of oil helped to fix the issue (for now). So we'll see. I'll keep yall posted.

[Ghostcloak]

So yeah. After I got home from work (20 min. drive), I checked compression

180psi
175psi
175psi
175psi..

Everything seems normal...

wtf...

[onlytrueromeo]

Your rings are worn but they seem to be working fine ones the engine is warmed up. Those aren't your problems. If you're getting a rough running, then your timing could be off..its been known that the belts jump, but it won't cause pre-ignition.

Get some seafoam for your engine first - undo the brake air hose on the driver side and sip seafoam into it. You will get lots of which smoke out the back of the car. Don't let the engine drink too much to stall it. This could help your rings and carbon deposits on your cylinders.

Checking your fluid level by checking the tank isn't the way to go, tho that shouldnt cause these problems. You will want to open your coolant fill cap when the engine is cool and check to make sure its topped off.

Jump the ten/gnd pins on the diagnostic panel and check the timing w/ a light. Try retarding the timing by rotating the distributor. If the engine jumped a tooth, then it won't fix it, not sure if it will make a difference, but it can't hurt.

Check spark plugs. This should actually be #1 w/ checking the ignition leads.

[Ghostcloak]

Well, it runs fine/smooth now. The only issue was the previous day when the car started and a loud knocking sound was coming from the head. Then, after letting the engine idle for about 2 minutes, it quieted down quite a bit. It runs fine now. No hesitation, vibrations, or puttering. Even cold starts sound normal as of now. I seafoamed the car about a year ago. Maybe I'll do it again. Spark plugs looked clean, although there is some carbon on the body of the plug (not the electrodes, but the end of the screw part/shell).

I'm going to let the car sit for about a week and then try to start it. If I see the same symptoms, then I'm going to assume it's the HLA's and have the head rebuilt.

[onlytrueromeo]

Put a BP in rather than spend a few hundred bones on getting your head rebuilt!