Need Help/Tricks Diagnosing valve? exhaust? misfire? noise

[ab_slack]

Our 99 Ranger w/ 3.0L and auto trans has developed a noise which we are having a tough time pinning down. The noise started faint and then got louder over a week or two.

The sound is somewhat ambiguous in nature to my ear. To my admittedly un-expert ear, it could be an exhaust leak, engine miss, or possibly some valve related issue.

The sound occurs only under load and appears to be coming from the engine compartment.

I am pretty certain that it is related to just one cylinder. Unlike a general exhaust leak before muffler where every cylinder firing is loud, all sound normal except for one. The one is more "loud" in that it stands out. It may in fact be a bit louder but perhaps more different than loud.

Power seems to be normal for this vehicle. I only drive it on rare occasion and power seems low to me compared to the Explorer and BII that I drive daily so hard for me to tell with any certainty.

It idles very smooth, no sort of intermittent miss. If a miss it is continuous while under load. Engine seems smooth but with it being under load it downshifts so RPMs tend to be up which could covers up roughness from a miss compared to at lower RPM.

If I were to make my best guess as to the noise at the moment I am thinking an exhaust leak between block and exhaust manifold right by one of the exhaust ports. I have no idea how to confirm this is the case. And if this guess is correct I am not sure how difficult it is to resolve.

My big fear is that there is a problem with one of the valves and under load it is allowing gasses to escape. I also know there is a condition with the valves, maybe lifter gap, that can cause a slapping sound when under load?

Vehicle has 144K miles on it, but engine was replaced not quite 3 years/30K miles ago by Ford with a factory rebuild/remanufactured engine.

So anyone have any tricks or tips for narrowing this down?

I was thinking of pulling one plug wire at a time, drive it s short distance each time, and see if one specifically changes the sound. Then pulling the plugs to see if they tell any story. And then perhaps doing a compression test on each cylinder. Though, if this only happens under load I am not sure if a basic compression test will reveal something happening dynamically like that.

Anyone have any other thoughts? Or those of you who know the 3.0L know what typical thing there may be? I know the 2.9L but that is a very different animal than the 3.0L. Never messed with a 3.0L so have no idea how easy/difficult it will be to get at the plugs, much less the typical behaviors/problems of the 3.0L engine.

Thanks in advance.

P.S. No CEL. I haven't hooked up to the OBD2 to see if any codes, kind of assumed with no CEL that there would be no codes, but I guess worth a try.

 

[straycat]

If it is a ticking noise....not to worry about it. This motor is normal for ticking. If it is a loud thumping noise than I would worry. Without hearing the noise it is hard to tell you what is wrong. If you could get an audible recording and post it that might help out. If not I would take it to a shop and have them look at it and have them run a diagnostic on it.

 

[RonD]

Cold engine
Loosen/remove "fan belt" so there is no fan noise, I have the fan clutch wrench set so remove the fan instead of the belt.
Start engine, it can run a few minutes without water pump.
If you have a "trusted" helper, they can put vehicle in gear(reverse, no one should be trusted that much, lol) and load up the engine a bit.

See if you can pin point the noise
Yes, removing 1 spark plug wire at a time can ID an exhaust manifold leak OR a failing connecting rod.
Don't run engine too long without water pump, you can test it again after cooling off, loosening fan belt is not that hard, lol.


A $25 vacuum gauge should be in every ones tool chest.
No matter what they add to the outside of an engine it is still basically a big air pump, so an air pressure gauge can be very handy.
Kinda like the switch to electronic controls, you switch the dwell meter for a volt/ohm meter

With engine warmed up you can hook up the vacuum gauge and tell alot about engine condition and problems.
Good read here on the info you can get with a few simple tests with vacuum gauge:
http://www.gregsengine.com/using-a-vacuum-gauge.html

 

[ab_slack]

I am pretty certain not a tick. Those stand out at low RPM and tend to occur load or not but I could be wrong.

Probably tricky to get recording of it, but maybe with fan not turning.... (good idea RonD).

I have a vacuum gauge so can do checks there.

I tried asking the mechanic at the shop but he couldn't ID it himself and I have doubts he recognized the specific sound I was referring to. I've had bad experiences at shops anytime there is any question about reproducing or identifying the issue so I figure I am more or less on my own with this mystery.

Last car I heard make a similar noise was a 72 Olds Cutlass with a V8.

 

[hopster]

Try using higher octane gas to rule out preignition.

 

[RonD]

One thing I forgot to mention was the EGR system, it is only used under load, so a leaking EGR valve would only be heard under load as it opened, leaking EGR pipe would be heard all the time.

With engine idling you can put a vacuum line on the EGR valve and "suck" it open a bit to try and hear if it is leaking.

 

[ab_slack]

Got working on this over the weekend with zero results.

Disconnected the fan the sound definitely seems to come from driver side and sounds low...louder underneath than above.

Pulled plugs on the driver side, all looked quite good. Gap was 5 mil large on one but others were right on, fixing the gap didn't make a difference.

Pulled wire off the plugs one at a time. Far as we could tell it did not change the noise at all and other seemed to make it run rougher as one would expect. Result was the same with all 6 plugs.

I am feeling a bit stumped as it seems like a single cylinder related noise and thus pulling wires should have localized it.

Only thing we stumbled across was that one of the wires (on drivers side) had a slice/crack in the insulation that goes down to wire, but it isn't near any metal and it seems to be firing. If it weren't I or not under load I would have expected to see something on the plug. The wires have over 100K miles on them so picked up a new set. Haven't put it on yet. Maybe is it the wire? Easy test, should have done it after getting the wires today.

Listening to the sound the best candidate would be at the coupling between the Y pipe and the driver side manifold, but from the top it sounds like it is lower. The more I listen the more it is starting to sound like a lifter tap or some something involving a lifter or cam.

We did compression test all three cylinders on the driver side and they were within 2psi of each other.

We also had been noting some fluid leaking, thought it was oil but while under it the rear of trans at the driver shaft has a bunch of dirt/sludge and not much forward although a few stray drops of oil. It is so much worse at the end of the trans that I am thinking maybe a seal problem at the trans output shaft.

 

[RonD]

You can try having someone holding their hand or rag over the cold tail pipe with engine at idle to see if you can flush out an exhaust leak.

But it is reading more like a main bearing knock from the description.

Valve train noises are not described as "knocks"(lower tone), they are "taps"(high tone), I know it is just semantics but first impression was "knock" and lower on the engine means rod or crank bearing.
A rod bearing knock comes from cylinder firing so will almost completely disappear when spark is removed.
Crank bearing just knocks.
Hopefully I am way off base with this.

 

[Campbell5149]

these motors are bad about piston slap too. I rebuilt mine and it still has a noise, I've put 30k on it so far and I'm not scared of it. unless its an audible clear knocking, or tick, I wouldn't worry too much. You can always get a cheap stethoscope and poke around and see exactly where your noise is.

 

[ab_slack]

Looks like a found it and I am hoping it is an easy fix. I used a wet towel and put it over things till I heard sound change. Then I localized it feeling exhaust gasses come out.

It is a leak at a blocking plate in a unused port in the exhaust manifold on the driver side. Below is a pic of it. I pulled the plate off, the gasket on the far side from the bolt blew out.

Now the problem if figuring out what this thing is called so I can get a new gasket.

Unless high temp silicon is high temp enough to do this right on the manifold.

Seems like a flakey design to me, getting any sort of compression pressure on the far side from the bolt seems pretty sketchy to me and any warping with time and it'll do exactly what it did.

Thank you for the ideas.

 

[RonD]

Permatex ultra copper will work, but I would also use a gasket.

Hit auto parts store and buy a square of exhaust gasket material or find an exhaust gasket you can cut down to fit