2.3L Knock

[daveesl]

Hi All,

This one is driving me nuts. 87 mustang, 2.3L EFI, 5 spd. Car has 140,000 miles on it.

There is an engine knock in the lower, rear passenger side area of the engine. Did a compression test with following results...
#1 - 160 lbs
#2 - 160 lbs
#3 - 180 lbs
#4 - 160 lbs

The knock comes and goes. It doesn't exist at idle, but only under acceleration, up to about 3 grand, then it goes away. Sitting still, you can barely catch the knock (for a second) during run-up from 1,500 to 3,000 rpm. Driving, it may be loud or it may be barely audible. The engine runs really smooth. Sometimes it will be loud, then I can stop for a minute, restart and the knock is almost gone.

I've tried all different grades of gas. I've gone through various oil viscosities. Oil pressure keeps at a steady 50 psi.

The thought is, rod bearing. However, I've also heard that the 2.3 had a problem with carbon build-up and this could be a cause. The knock sounds like it is coming from the area of cyl 3-4, so with the high pressure on 3, my thought is maybe carbon?

Anyone else run into this. Sooner or later, I'll get around to rebuilding the engine, but for now I enjoy just playing with the car (it is my $450 toy). I just don't want to take the chance of throwing a rod. If it is a rod, it gets parked, if it is carbon, then I'll continue to play.

Thanks in advance,

Dave

 

[JamesBaumann]

Im thinking that considering the acceleration is still smooth, the compression is relatively close on all four cylinders, and the knock goes away once it has been restarted, then the internal engine components are ok. Usually when something inside your engine has gone haywire the car will run really rough because it is pretty well completely missing the fire on that cylinder, so there is a very substantial misfire. Also, considering your oil pressure seems to be good, often it will drop substantially when something inside the engine is malfunctioing. Go ahead and have a look at your timing. If you don't know how then here is a link for a how-to.

http://projecthp.ford23.com/tech.html

If this is still beyond you then get somebody at your local auto shop to take a look/adjust it, it's not very expensive.

If it is infact carbon then you can think of doing an engine flush. I'm not sure how well this stuff works, but I have seen it around. It just comes in a bottle in the auto fluid additive section on the parts store. Read directions for use, but I think you are just supposed to add it to your crankcase, run the engine for 5-10 minutes, then drain your oil and change it. Hopefully that will help a little with the carbon build-up.

Then of course, last but not least, check things like your spark plugs, ignition wires, distributor cap & rotor, all those little tune-up parts. Perhaps even just your #3 spark plug electrode is worn out or something as simple as that.

If all this doesn't work then come back and tell us and we'll try to figure out what else it could be. Hope this helps though, good luck!

 

[i4power]

I wouldn't do an engine flush if I were you...cleaning out the carbon and gummed up oil might cause your engine to consume oil, because they might be filling in spots that would cause leaks otherwise. This might especially be true on a 140,000 mile car. Is this just an old-wives' tale?

 

[Ray III]

If you flush your lubrication system there is a chance of making oil seals leak.

CARBON on the other hand, inside the intake and combustion chambers, is never welcome.

 

[JamesBaumann]

I wouldn't do an engine flush if I were you...cleaning out the carbon and gummed up oil might cause your engine to consume oil, because they might be filling in spots that would cause leaks otherwise. This might especially be true on a 140,000 mile car. Is this just an old-wives' tale?

I had no idea.

 

[TurboFlush]

run fuel injector cleaner or something like that. normally engine cleaner should not be needed.
I used a bottle of this when I heard knocking in my current project, just for ****s and grins. It made the motor alot louder. and reinforced the fact that the bearings were gone in my motor.

If the bearings are starting to go bad then you might not be able to hear it untill the oil gets warm and thin. 9how mine was)
is it a Ping, Knock or a Rattle?

If it was anythin in the Ignition I would say the car would not idle or acelerate right. but you say it is fine. I am thinking the worst! sorry

 

[TurboFlush]

P.S. the motor of mine is now in many peices waiting to be cleaned and awaiting a massive order of parts.