Ping or rattle?

[kerrye]

On my 94 I have a noise. I thought it was pinging. Switched to hi-test fuel. No difference. Could be a rattle. Thought maybe a heat shield. Can't find a loose one. Makes the noise under load. Not evident with slow acceleration on the flat. Omnipresent under heavy acceleration or uphill. Any good ideas on how to chase it down? My check engine light comes on frequently but everytime I've checked it, it's the EGR code.

 

[crooozer]

I bet your timing is slightly out. Check it and report back. I spent MONTHS chasing the same problem you had, no-one here was able to help and it was only by accident I located the small timing difference.

 

[kerrye]

Slightly? Try 16 or 17 degrees advanced! Thanks for that advice. I suppose I should have checked the timing right away instead of switching fuels. I haven't driven it up a big hill yet but under heavy acceleration in the neighborhood, no pinging. Now I can switch back to regular fuel I guess.

 

[rolliges]

Try searching (google first, then Mud) about EGR and "pinging."

Does it ping with a cold engine? If not, could be EGR.

Does it ping with warm engine while cruising or under moderate load? If so, could be EGR.

Does it ping with warm engine and WOT? If not, could be EGR.

I suggest searching Google first Because there are many nonbelievers on Mud regarding the relationship between EGR and "pinging."

Keep an open mind.
Good luck

 

[landtoy80]

Check the bracket on the pass side of the sway bar near the end. There is a bracket (thinks its for diff lock) that has came lose on my 94. Made rattle noise but not all the time. I put black tape in it and rattle is gone. Loose heat shields on exhaust before the cat made a noise too, it was rusted so I pulled it. Cat shield rattles too. Broken sway bar mount at the end also makes a low end noise rattle at different rpms.

 

[crooozer]

Glad to be of assistance

Slightly? Try 16 or 17 degrees advanced! Thanks for that advice. I suppose I should have checked the timing right away instead of switching fuels. I haven't driven it up a big hill yet but under heavy acceleration in the neighborhood, no pinging. Now I can switch back to regular fuel I guess.