leadbrick

I looked/searched around and there seem to be many reasons for a rattle/tick from an engine. The most hopeful would be a loose heat shield or something. It could also be the valves or pinging from detonation. Or it could be something worse from the internals of the engine...

I'm not sure how to separate out which it might be, so I thought asking might be helpful. I don't really mind the sound, but if it will cause problems I do want to take action. The previous owner said he drove with it for 50k miles and just turned up the music so it didn't bother him... I'm not sure how much I believe him, but he did say that.

The sound sounds like a rattle that doesn't change. The rate of the rattle/tick is about as fast as the noise that a kid might make if he put baseball cards into the spokes of his bicycle and went down a hill. It does get louder, but not quicker or slower. If the car is out of gear, the noise wont be present. The engine needs to be under load for the sound to show up. The more load, the louder the noise. In the driveway it wont be heard. Sitting in the drive way I can hear the valves or maybe the injectors clicking when poking about in the engine compartment, but that isn't the noise I'm worried about. I think this means it is not some loose shield, since that would not come and go with load, just road speed. I also think it is not some physical part of the engine, since that should change with RPMs. Does that sound right?

The noise is not present at idle, comes in around 2k and by 4k rpms, the engine (or road) is too loud to hear it. It is not all that loud, you do have to listen for it. Taking and freeway driving can almost overcome it. It does get louder with load though. Going 60mph down the freeway I will hear it for sure. At that speed the rpm's are around 3k. If i take my foot off the accelerator, then the sound instantly disappears. Hence it is not present during engine compression.

I'm inclined to think it's not a big deal since the noise isn't that loud, and the gas mileage is pretty good (37 mpg or so). I believe that if it was pinging/detonating the mileage would drop. Is that just something I made up in my head? The power is fine too, the engine moves the car as good or better then my parents old '93 accord. I'm confident that car is in good condition, so I think the power in this one is also fine. Again, I think the power would suck if it was misfiring that much. Also it passed emissions just fine, though I don't know what that could rule out.

I've had the car about 2 weeks. It's an 1988 Civic LX with 152k miles that were mostly owned by some old lady. What do you think?

Furyof4

Retard you ignition timing or try higher octane fuel and see if the noise goes away. If it does then its detonation if not at least you ruled it out.

leadbrick

That sounds like a good idea. Actually the previous owner had been using premium fuel for some time. (He thought that regular gas was just bad/cheap and was bad for cars). I thought that might have been the issue, so I have started putting in regular grade. The noise has not changed.

I guess that means it is not detonation. If it was it should have gotten worse when I switched to regular, right?


Another idea: Could it be the engine retarding the timing itself? Does that make a sound?

spoonfedcrx

It would be too far advanced that would cause detonation. I would check ignition timing and pull your plugs and see how they look. What kind of ignition parts and plugs you running?

jhmed9

are you having any trouble with the tranny? make any funky noise while starting? hesitation/slow start? have you noticed any smoke from your exhaust?

if it runs fine and isnt missing, i wouldnt assume that it needed plugs or any of that good stuff, but yea itd be a good indication of rich/lean problem. but detonation problems wouldnt help that mpg any at all.

it kinda sounds like something is loose somewhere. something that isnt needed for the rotating assembly. maybe one of a few bolts that hold something together wiggled out and is rattling around in the bottom.

if you gave your car gas when its out of gear, will it make this noise? or only in gear?
if its only when its in gear id starting looking towards the tranny's side of the bay.

leadbrick

Yea, took awhile to get back here, but here is what I found..

I took the spark plugs out. They looked funny, so I compared them to my parents '93 Accord. I thought the tip was a bit too white (maybe lean?), but it was similar to the Accord so I believe that the plugs are alright. Of the 4 spark plugs, one was dripping in oil. That probably is the cause of the engine eating oil, but not of the noise afaik. So, the plugs looked more or less fine.

The ignition parts and plugs are all stock, I believe. I didn't take note of the brand of plugs, but it was a normal looking one. If you think it is important, I can check it out tomorrow. I don't understand how the plugs or wires could cause this issue though. I can see how the plugs might tell of a problem, but even if they are some shitty cheapo ones, they might cause misfiring, sputtering or something, but not rattling, right?

The transmission is rock solid. No noises or issues with that. The clutch is also just fine. No smoke from the exhaust either. I kind of think there might be a slow start/hesitation issue, but since this car has less power then most I've driven, I attribute it to just having no power under 2.5k.

"if you gave your car gas when its out of gear, will it make this noise? or only in gear?"
Nope, Out of gear it just spins the engine quietly.

Some days it is really loud, some its hardly noticeable. Seems to be worse when cold. It's almost as if it is the same issue as if you drove around with an engine that was permanently a little cold. I think the engine changes the timing when cold, doesn't it? Whatever parts tell the engine that it has reached operating temp seem to be working fine, because the idle doesn't stay up at 1.5k, but will soon drop to a normal idle of 8-9k.

With symptoms of that it only comes when under load, could it be timing? valve clearance? Does the fact that the noise's volume gets louder/quieter (note: not frequency) with engine effort (not RPM) matter?