arsxj

What is detonation, what does it sound like and what are the most common things that cause it. Also would it contribute to the engine running rough?

98 JeepJeep

detonation is the ignition of fuel without spark...mainly caused by running lean..it sounds like pinging...and can be fatal to a engine...

Abovetimberline

x2,also called pre ingnition,it can be caused by poor fuel,lean mixture,carbon built up on the combustion chamber,out of time,it will cause overheating on the head and since it is actually cause the the fuel to ingnite you will loose power as it is trying to push the piston back down before it reaches tdc.

98 JeepJeep

and you can blow heads gaskets...got a pile of them from the mustang to prove it!!

arsxj

Would a bad o2 sensor cause this? I'm starting to think my o2 sensor is bad because it runs rough alot but it is intermitent. Today it was running rough and when I got home it was running fine but still making this noise. As I accelerate it starts to sound like a diesel truck as the rpm's get higher if I let off the gas it will get alot louder for a second the completly dissapear. If it were a bearing or something would'nt it do it all the time?

Abovetimberline

Yes it can,low fuel pressure can also cause it,try a higher grade of fuel to see if it stops,if it does then it is more than likley running lean.

arsxj

I ran it down low on fuel and filled it with 93 octane and it made no difference.

SeriousOffroad

Describe the sound you are hearing.

RENIXBEAST

It could be an oil pump but until you describe the sound, It could be a few things.

arsxj

It sounds like a diesel truck thats the best way I can describe it. About a month back my oil pressure gage quit working. I replaced the sender and it still doesnt work. I drive it 60 miles a day 5 days a week and it runs fine other than this noise and running rough under around 1500 rpm's. I had the oil changed at a quick lube and im sure they put cheap 5w oil in it and now 2000 miles later I know it has thinned out. I guess I'll put some 20w-50 in it this weekend and see what happens. Any more ideas?

SeriousOffroad

Does the sound increase with engine speed?
Does it sound more like a rattle if you bump the throttle quickly?

arsxj

It does insrease with engine speed.

If I bump the throttle nothing happens. As soon as I let off the throttle it gets louder as there is no longer a load on the engine and then it dissaears all together. All this on about 1 second.

If I rev it up in neutral it will only slightly make the noise at very high rpm's.

Abovetimberline

What you just described is not pre ignition,it sounds like your flexplate,might want to check for cracks around the center of it.

SeriousOffroad

And the only way to check for cracks is to pull the tranny. Been there, done that...

Check your Torque Converter bolts first.

Abovetimberline

Actually the first time I had this happen I took it to a friends shop,he put it up on the hoist and took out his little maglite and said there is the issue,small crack. Took it home and replaced it. It is actually easy to see,may have to turn it over but you can do it.
But I agree the bolts can be loose also.