knock from bad gas?

[cordes]

I was traveling home today on the freeway from IL, and on the way back I noticed a little bit of a ticking noise. I usually jam to a good CD and sing a long in a horrible tone as to try not to fall asleep. However durring a lull in the action I noticed that the slight ticking noise that I had attributed to one of the many creeks in the 16 year old car was actually more like a little guy in the engine with a jack hammer going to town.

I then figured that it was knock, and when I lifted the throttle just a little, it would lessen, and when I would put my foot back into it, it would start right back up again.

Unfortunatly this was toward the very end of my trip, and I stopped for gas at my place of employment due to the fact that I know it is good.

This knock, which is really horrific when leaving traffic lights when I hit about 2200 RPM has not subsided in the 5mi or so that I have driven the car since my fill up, and I am quite concerned that I have done some damage.

One interesting thing to note, that if I put my foot in it a little farther, to the point where it is WOT, I believe, it does not knock. It is a stg. 5 cal, so I am not sure what the fuel curves look like on part throttle.

Any advise or suggestions would be appreciated, as I don't want to do any further damage.

Sorry for the long post.

[89ShelbyGuy]

Whats the status on the engine..rebuilt? stock?
Rod bearing most common...when you say horrific it only leads me to beleive its a rod bearing about to go....

Or a lifter issue? i would pop the valve cover and take a peak at the lifters...

I have a nice knocking/clanking noise coming from my rebuilt 2.5.....replaced the lifters..helped the noise a tad bit...i can't tell if its piston slap or rod knock....

Heres a rod knock video file...http://www.thermactor.com/rodknock.wmv
Mine Diffiently doesn't sound like that...how about yours?

Maybe change the oil? See if any metal flakes are in there?
Or pull your dipstick out and really look at the oil?


do you have a A/f gauge? What was it reading after the gas?

Hope this helps yea

Tom

[Dave]

Sounds like a bearing or a few. Maybe dying oil pump?? Obviously it's not detonation as that's at much higher boost levels at any given throttle percentage, but sounds to me like either not enough oil pressure, or some toasty rod/main bearings.

Check the oil sir.

[Murphy]

if it sounds like the vid, pull the oil pan and check all the bearings by removing the rod caps....mine sounded like that and they all felt fine with the cpas on but once i pulled them off #4 was toast

[cordes]

It must be rod knock, as I have put many miles on my car with the new gas in it with no positive change. I was really hoping it was just some pinging due to bad gas, but oh well.

It is no were near as bad as that video yet, but I don't want it to get there either.

Thanks for the suggestions guys.

[89ShelbyGuy]

Get a video of yours....mine has to have piston slap..cause after the oil gets warm and the car is at normal temp the noise is barly heard and if it is, it sounds like a desiel engine...so....

But i don't think you can just develop piston slap?? Dave?

Tom

[Turbodave]

As far as developing piston slap, that would be something that can happen over time, but isn't very common on these motors. The older ones are known for getting loose wristpins that make noise, but I've seen a few K-cars run for another 100k miles after the wristpin noise started without any problems.

A rod knock at the early stages is typically quieter when the car is cold and the oil is thin, it gets more pronounced once the engine is warmed up. It usually get's quieter under heavy throttle but louder under light throttle or decel.

If the rod bearing didn't spin and damage the connecting rod, and the crank wasn't damaged a bearing replacement may save the engine. If it's really loud chances are the bearing spun and damaged both the rod and the crank.

Tom, what kind of pistons did you use when you rebuilt your motor? Forged pistons are notorious for being noisy (piston slap) when cold due to the bigger tolerances needed for their bores. Once they warm up they usually quiet down.

[mech1nxh]

It must be rod knock, as I have put many miles on my car with the new gas in it with no positive change. I was really hoping it was just some pinging due to bad gas, but oh well.

It is no were near as bad as that video yet, but I don't want it to get there either.

Thanks for the suggestions guys.

just playing devils advocate here......"traditionally"....winter to summer fuel
blends start around april....try a different fill up from a high volume name
brand supplier

p.s....could be wrong here but a clearance issue would cause more "noise"
under a progressive load???...knock sensor equipted??

[cordes]

just playing devils advocate here......"traditionally"....winter to summer fuel
blends start around april....try a different fill up from a high volume name
brand supplier

p.s....could be wrong here but a clearance issue would cause more "noise"
under a progressive load???...knock sensor equipted??


I filled up the other day at work which is known good gas, and after about 30mi the noise is still there. The knock sensor is in there and I assume that it is doing its job. I guess I will have to change out the bearings and see.

[89ShelbyGuy]

Hey dave..i have new 2.5 .030 over mahles in there..I am more and more on the side of piston slap. due to the fact at a cold start up it sounds like a clanking..and once i drive the car for about 10-15 minutes...and when i come to a stop it almost is no tthere....maybe a TAD bit..but you can't really here it..

[3Bar_Mopar]

I had a similar problem the other day....turns out I had a wrench sitting on bare metal that resonated at a certain RPM.....sounded like rod knock..

[cordes]

I had a similar problem the other day....turns out I had a wrench sitting on bare metal that resonated at a certain RPM.....sounded like rod knock..

yeah, I checked around for anything that would make a noise like that, but I just could not find anything.

[cordes]

In what will most likly be the final update to this thread, I replaced the rod bearings and it is still knocking. However, the journals don't look so bad, so I will just have the bottom end rebuild which should not cost me too much since I cought it early.