ATX rod bearing clatter

[revhardSHO]

How serious is this? Occasionally if I punch the gas from a dead stop I can hear the bearings clatter before the rpms pick up. The engine speed will drop down to ~500-600rpm. The clatter lasts for about .2-.5 seconds and doesnt occur all the time. The red oil light sometimes comes on during the clatter, other times it does not (I would say 50/50). The 145K motor is pretty healthy and runs quite strong, no knocking or oil consumption, but Im afraid it may be time for a rod bearing change for safty sake. Thoughts?

 

[40BelowSummer]

I would do the rod bearings for the insurance especially when your debating whether you should or not. If it spins a bearing you will really wish you had. Plus you'll probably do it sooner or later right?

Ask autobahnSHO for an opinion.

 

[Slo-Sho]

That could possibly be "pinging". Try decarbon'ing your motor with Seafoam (it's good isht). Or if you aren't already, you can try using a higher grade of gasoline. The oil light would be from the rpm's dipping that low.

 

[revhardSHO]

That could possibly be "pinging". Try decarbon'ing your motor with Seafoam (it's good isht). Or if you aren't already, you can try using a higher grade of gasoline. The oil light would be from the rpm's dipping that low.

Im pretty sure its rod bearing clatter, although I will try the seafoam too. I have a full set of rod bearings I was going to use on the 89 but I guess they will be going in the 94 instead. I dont see why the rpms dip like that, its not really hesitation, more of a delay, if that makes any sense. Thanks for the help.

 

[Slo-Sho]

Often times when rod bearing failure is iminent, it will manifest itself in a faint knocking at idle and upon deceleration. Good luck.

 

[TYSHO]

It would be a good idea the check the level of your oil, too.

As suggested, decarbon the intake and run some higher octane.

 

[HopefulSHO]

If you're laying into the throttle, and your RPMs drop to 500-600 you've got other issues as well. RPMs on an ATX should never get that low..
Is the sound kind-of high pitched? I agree it kind-of sounds like a mild case of preignition too.

 

[Mr Anonymous]

I would tend to agree that it sounds more like a timing and/or mixture issue resulting in knocking/pinging since it only occurs when you describe. Start by running the KOER tests and testing the knock sensor. It might not be doing its job well anymore. You might also want to consider replacing the O2's if you get any O2 codes or if they've got more than ~80K miles on them.

My '92 with 194K had two bad O2's and a bad knock sensor so it was running pretty lean most of the time and I got the same noise mashing the gas in 1st or 2nd, even on rod bearings with less than 10K. Replacing the O2's helped a lot, and I get the noise a lot less frequently. I just haven't had the time to dig in to get to the knock sensor yet.

 

[Bizzy]

if there is carbon buildup on the piston top, you can get a knocking sound from the piston hitting the top of the head. The 3.2 bore leaves a small amount of the piston that could hit the head if there was a good amt of carbon on there. 3.0 combustion chamber is used in both a 3.0 and 3.2.

 

[F-22 Raptor SHO]

if there is carbon buildup on the piston top, you can get a knocking sound from the piston hitting the top of the head. The 3.2 bore leaves a small amount of the piston that could hit the head if there was a good amt of carbon on there. 3.0 combustion chamber is used in both a 3.0 and 3.2.

this is news to me. never heard of this

 

[Bizzy]

what part have you never heard about? The 3.0 and 3.2 head having the exact same size combustion chamber? Or carbon hitting the head from the top of the piston?

Believe me both are true and the latter is possible. Albeit that the engine would have to have some serious issues to build up that amount of carbon. Remember when at the TDC of the stroke, both 3.0 and 3.2 are nearly flush to the top of the cylinder. Now you have a 89.5mm (i think) diameter combustion chamber (3.0), but the 3.2 pistons are like 92mm (i think) tell me that if there is a build up of carbon it's not gonna smack the heads.

 

[Slo-Sho]

Possible...Yes, probable....No. You are correct in saying that a motor would have to have some major malfunction for carbon to build up like that, possibly on a 500k untouched motor??? Anyone?

 

[SolidState]

I agree with chris on this one....my ATX has new rod bearings in it and I have the same problem. but I am running pig rich. I am planning on replacing the knock sensor, cleaning the injectors and running a decarbon procedure...