HELP! Engine rattle/knock worsening since fuel additive/premium ga Options

[celicakitten]

Please help with any input as I'd like to get the knowledge of people who really know these cars! I just bought this car and am discovering some issues(as expected) that I'd like to sort out before going to the dealer or hopefully finding a good local mechanic to help me!

Here are some stats before I describe the main issue:

-97 Celica ST 5spd Stock-original engine/transmission
-192,xxx miles
Guy I bought it from recently replaced the:
-timing belt
-spark plugs/wires
-distributor(looks fairly new at least)

Everything works, passes emissions, shifts great, and idles perfect other then a little vibration when the air is turned off. What my main concern is that initially there was a slight rattle/knock on start up and occasionally at higher speeds(inaudiable if the radio was even slightly on). I tried to chalk it up to the bar that holds the hood up as the clip to hold it down in place was broke. 2 days ago I topped her off with 91 octane and a bottle of chevrons fuel system cleaner, and on day 1 the car seemed to respond quickly and perform even smoother.

BUT...

On day 2 the rattle/knocking noise became more apparent continually getting louder (although my paranoia/turning off the radio may also play a part), and is now almost constant! Only time I don't hear it is when the car is idling. I drove it 14 miles each way to work and back(mostly freeway) for 2 nights, and as of this morning I fear to drive it if there is a real issue with the engine. I put her in neutral and pulled the throttle to try and verify that the engine is making the noise...there's slight noise on the rev and then knock knock knock back down to a quiet idle. I had to replace the motor mounts on my old celica and this is nothing near the same noise, so I'm almost positive it's not that. When the engine cools off I will inspect the spark plugs/wires/wiring...maybe distributor? I'm afraid too many deposits have been loosened, but am curious if it could be anything else and what/if anything I can do to fix it!!! I know it's an old car and there's a good chance it may be the engines time...but I really hope not! I'd like to minimize my expenses until the time is right for an engine swap and still use this car as a daily driver around town. Any help or suggestions would be greatly appreciated!!! Thanks in advance!

This post has been edited by celicakitten: Jun 3, 2012 - 11:21 AM

[celicakitten]

I swore my 7a knocked, but when I would let others hear it, they would claim I was crazy, or just looking for a reason to get rid of the engine. Not saying that is your case at all, but I would def check oil first to see whats going on, and tell us of any performance loss.

And or block explosions =)

Haha! NO block explosions please!!! I do seem to have a bit of paranoia when it comes to these things, even when I shouldn't so I get what you mean

Step one-check oil level, refill if low

Step Two- drain oil into a clean container and check for metal at the bottom or a metallic sheen to your oil.


If the above two items are okay, perform a simple cylinder balance test. With the engine running carefully unplug one spark plug wire at a time and try to determine if unplugging any one cylinder drops the rpms less than the others.

Step one-checked
Step two-not done just yet, just had the oil changed two weeks ago(but a good idea none the less).
I was about to do a cylinder balance test, but upon checking the spark plugs and wires once the engine cooled I found that one wire(furthest from the distributor) had snapped off in the connector to the spark plug. I had to use pliers to pull the rest of it off the spark plug, the guy I bought the car from must have bought a really cheap set of wires so now I need to buy new ones...any suggestions?

I also discovered my exhaust manifold heat shield is missing bolts and some of the ones left were loose(slight rattling there), and upon closer inspection of the exhaust manifold itself there is a large crack. That would explain the slight exhaust leak/smell I get inside the car, so I will also be replacing that soon...again any suggestions on parts you guys recommend is greatly appreciated!

Hopefully once I get those wires replaced it will decrease, if not stop altogether, the knocking sound I'm getting. I does look as though I have a small leak in addition to the power steering one I knew about as the last couple days(since the knock started) the leak has increased. I'll have to keep an eye on it since there could be damage from the pressure building up from the spark plug not firing and like mentioned earlier the deposits that may have been preventing a leak being dissolved from the fuel additive.