Detonation problem

[KiltedBanshees93GT]

Well, I've decided that my car hates me . Lately I've noticed that shes started knocking, lightly at first, but its gotten worse as time went on. It only occurs (that I've been able to tell) at lower rpm, 1500 and below,when going uphill. if I drop a gear and get the rpm back up toward 2k it seems to stop or diminish to the point I cant hear it over the exhaust. The big thing I dont get is that I've had to get on it a few times, and it doesent seem to knock on heavy throttle, just at lower rpm while going uphill.
I've had the car for like 7 years and never had any problems like this. Timing is at the factory 10degrees, I've tried higher octane (helps but doesent fix), run 2 bottles of fuel system cleaner (didnt make that much difference), car is running at normal temp, etc.
I know the car needs a tune up, which I'll do this weekend if the temps come up a bit, but can anyone think of anything else to look at? Dirty fuel filter maybe? I havent changed that in a good while.

Between this and the tranny starting to whine, it seems like I'll never get her back to 100%

Help,
J

[GhettoPop]

well, since they are due anyway, i would change the plugs, wires, cap, rotor, pvc valve, and fuel filter. cheap stuff that needs to be done anyway, if your problem is still there afterward, at least u can cross those off the list of possibilities.

[KiltedBanshees93GT]

Thats the plan for this weekend, except the wires (they are only like 6-8 mos old). I just thought it odd that it doesent seem to do it under heavy throttle. Only when cruising uphills.

Maybe the altitude causing it to run lean? The car was at sea-level its whole life, and then we moved up here in the mountains. Would 1k feet make a difference? (throwing out ideas at this point)

Thanks,
J

[USMC302]

Yes, the octane rating decreases as you go up in elevation, but you said you tried the highest with no changes, let us know if problem still persists after a plug and fuel filter change.

[agardonia]

hate to break it to you Kilted Banshee, but if it's doing what you say it is at that rpm range, that's not your engine knocking, that's your main bearings rattling. If I were you, I would baby that thing, until you can pull the motor and replace them. If you get on it, you could lock up the crank or throw a rod through the side of your block, and then you will be screwed. Any decent mechanic can take care of that for about 400 or 500 bucks, depending on how much the shop charges. I would get that fixed asap, or just rebuild the motor. The reason I know this is because my mustang does the exact same thiing...I get between 1200 - 2300 rpm, and it rattles, but if i get above that it stops. That's your main bearings...i would take care of that asap, or park it.

later

Andrew

[Ieatcamaros]

What's the oil pressure been reading?

[agardonia]

the needle always stays in between the middle and the low mark on my mustang for the oil pressure, plus i can hear the bearings rattle when i take off. I don't know about the other guys mustang that put the original post on.

Andrew

[KiltedBanshees93GT]

agardonia: Well, thats a less than comforting scenario, Is there any way to check to verify thats the problem short of yanking the engine?

Ieatcamaros:The oil pressure stays at the middle, but I have to keep an eye on it since she burns oil on 2 cylinders.

*worrying now*

[Ieatcamaros]

Does it do it at idle? It could possibly be the bearings but I'd check into it a little further first. With the engine running, pull each plug wire off one at a time. With bearing knock, the sound will decrease when certain cylinders are not firing. It is easier to pull the plug wires off at the distributor. I like to pull all of them off and just lay them back in place. It makes for easy removal. If you have never done this, I will warn you that they tend to "bite" a little. PKRWUD has a good write up on these types of things. I will try to find it for ya.

[Ieatcamaros]

Wow! that didn't take long to find. Here it is.
A little info on bottom end engine noises:


Main Bearing Knock:
Main bearing knock is usually apparent when the engine is pulling hard, when an engine is started, during acceleration, or at speeds above 35 mph.

Loose Flywheel or Broken Flexplate:
A loose flywheel or broken flexplate can usually be detected by this procedure:
1) Advance engine idle to 2000 rpm.
2) Turn off the ignition switch.
3) When the engine has almost stopped, turn the switch on again.
4) Repeat this procedure several times.
5) If the flywheel is loose or the flexplate is broken, a distinct knock will be heard every time the ignition switch is turned back on.

Harmonic Balancer:
A separated harmonic balancer will generally produce a heavy rattling noise that can be heard at low speed.

Rod Knock:
Excessive connecting rod bearing clearance noises are usually a light rap or clatter much less in intensity than main bearing knocks and the loudest when the engine is "floating" or running with a light load at from 25 to 35 mph. The noise will become louder as engine speed is increased. By grounding out each of the spark plugs, one at a time, you can determine from which cylinder the noise is coming. The noise may not be eliminated entirely by grounding, but it will be reduced considerably in intensity. The easiest way to ground out the cylinders is by inserting a 1.5" piece of 5/32" vacuum hose on each terminal on the distributor cap, and then placing the spark plug wires over the vacuum hose. With the alligator clip end of a non-powered 12 volt test lamp attached to ground, touch the test light tip to the vacuum hose to ground out that cylinder.

Piston Slap:
Piston slap is loudest when the engine is cold, and lessens or disappears after the engine is warm. When driving the car (at from 25 to 30 mph) the noise will increase in intensity as the throttle is opened and additional load is applied. To detect piston slap, try the following procedure:
1) Pour several ounces of 40 weight engine oil into the suspected cylinder(s).
2) Crank the engine for several revolutions with the ignition turned off. This will allow for the oil to work itself down past the rings and act as a cushion.
3) Install the spark plug(s).
4) Start the engine.
5) If the noise is eliminated, the engine has a piston slap condition.

Piston Pin Noises:
Piston pin noise is usually the result of excessive piston pin clearance. This will cause a sharp, metallic, double-knock sound most noticable when the engine is idling. Sometimes the noise is more audible at car speeds of from 25 to 35 mph. To test for excessive piston pin clearance noise, use this procedure:
1) Run the engine at idle speed.
2) Retard the spark to reduce the intensity of the knock.
3) Return the spark timing to the normal setting.
4) Short out each spark plug, one at a time. The double-knock sound will become more audible at the cylinder with the loose pin.

Other possibilities for you to consider include:
1) Loose timing chain hitting the inside of the front cover.
2) Connecting rod bolts hitting the inside of a dented oil pan.

[agardonia]

KiltedBanshee,

The best thing I can tell you to do is take it to the Ford Dealership and pay the cheap diagnostic fee to find out what the problem truly is. However, from the way you are talking, it does sound like main bearing problems. If it is in fact main bearing problems, then you might as well figure on rebuilding your motor, and if you're gonna do that, you might as well build your motor the way you want it. I know it sucks, but that's about the best course of action for this scenario. Good Luck and let me know what you find out.

Andrew

[KiltedBanshees93GT]

Thanks for the info guys,
I dont know which way I'm going to have to jump on this, since there is no noise at idle to allow me to test. (And the critera for the bearing noise don't apply in a lot of ways. Starting seems ok, a little more valvetrain noise than usual until the psi comes up [also running 20-50 oil because of oil burning], above 35 is ok, depending on the gear and speed. 45 in 4th is fine, but in 5th gets knocking when I go uphill. (@ about 1500-1700 rpm). if I hit the hill at like 1800-2k in 5th, it doesnt do it as much, but I still have to let off the gas to avoid knock as I go up. (As it starts I back off the throttle or downshift)
She hasnt had the most pampered life, but aside from a very light bit of tapping, especially on startup in the cold, the idle sounds fine. I guess my best option is to get the tune up done and then see. (Dont know if its going to happen this weekend due to sub-20 temps.) God I need a garage .
I really hope its not the bearings, I already have one stang in need of a rebuild.
Thanks for the input, and keep it coming,
J

[Ieatcamaros]

So let me get this straight. Your car knocks only at low rpm under a load? Does it knock if it is just sitting in the driveway at the same rpm? I know you said once it gets to around 2000 rpm you can't hear it, what about in the driveway? Usually with main bearing problems, when you throttle it up fast, your oil pressure will drop instead of increase. Try this and post the results.

[KiltedBanshees93GT]

Originally Posted by Ieatcamaros

So let me get this straight. Your car knocks only at low rpm under a load? Does it knock if it is just sitting in the driveway at the same rpm? I know you said once it gets to around 2000 rpm you can't hear it, what about in the driveway? Usually with main bearing problems, when you throttle it up fast, your oil pressure will drop instead of increase. Try this and post the results.

Nope, sitting still you can throttle up to 2k with no undue noise. The oil pressure is ok, the only time I ever see it drop is if the level has gotten a bit low, then coming to a quick stop the pressure will drop a bit as the oil sloshes around.

Rev: I've thought about the sensor, but wouldnt the car show a code on startup if it went bad?

Thanks for the help so far folks,
J

[5.0 Fiend]

Colapsed lifter maybe? On my last engine, I changed the oil to valvoline 20/50, and when I started the car, it had this awful knocking (so bad, my buddy half a mile away heard it), I tried playing with the dist to see if it was fuel knock, didnt help, tried pulling plug wires, no change, took it for a test drive and thought it would be safe to drive 15 miles to work the next day. On my way to work, I got tired of the noise and decided to hop on it to drown out the noise, and at about 4500 rpm it stopped, then I was like finally! The next thing I know, the car goes pop, and I look in the rear view to see a giant cloud of whiteish black smoke, got out and looked under the car, and sure enough there was oil and coolant coming out, (luckily I was about a mile from my house). As it turned out, I put a rod through the oil pan,(guess the new oil put too much stress on the motor). Oddly enough, the car started, but only wanted to run on a couple of cylinders. I guess your options are baby it, rebuild, or replace, it sucks to have your stang out of commision for any amount of time.

[KiltedBanshees93GT]

I dont think thats the case, she's been running 20-50 for like 8 months, no abnormal lifter noise, and the car seems to do fine except when a heavier than normal load is placed on the engine at lower rpm.
Oddly enough, the car seems to have the biggest problem when I'm heading to work, then on the way back, it seems to happen less often. Odd considering I'm driving the same roads. Maybe theres something with my driving style, or I'm just usually too whipped to notice it on the way back

J

[Rev]

Knock sensor?

Rev