Well I have a ticking noise that I cant seem to find. It only happens during medium throttle like accelerating up a hill or geeting on the freeway. It doesnt matter whether its hot or cold. Things I have checked: all fluids are good, currently no front driveshaft, rear drivshaft u joints are good, checked the flexplate and that was tight, and nothing appears to be loose underneath. Its also a fairly new motor with about 25k miles on it.

 

Leak in exhaust somewhere maybe?

Worn motor mount or something? Could be LOTS of things.

Where is the noise coming from?

 

Sounds like it s coming from the motor but its hard to tell. New exhaust all the back and welded the manifold when I replaced the motor as well as new motor nounts.Its one of those things I figured I would ask just to get some ideas.

 

I should also throw in it only happens in drive.

 

broken/loose flex plate bolts, or leaking exhaust manifold gasket would be my starting points

 

All symptoms of an exhaust leak.

Welding manifolds very seldom lasts.

Do a smoke test.

 

Agreed on all of that. I was just helping a friend with his Tundra last week. I had him power brake it and found the exhaust leak in a few seconds with my hand, (funky doughnut). Welding cast iron is plenty tricky even for pros I guess.

Then you might check those converter bolts just in case something went wrong there, easy enough!

 

is your fan hitting anything under load?

 

Could be spark knock. All that would be is you'd have to adjust your timing.

 

Timing is not adjustable on 87.

Wet rag in tailpipe, 2 shots of oil in the TB, strong flashlight, go under and look. - easy!

Or pay a muffler shop to look.

'87 manifolds are not cast - thin steel, still very hard to weld. Outside looks good, inside is rusted away. You just chase the hole around. cracks almost immediately.

Yes, I've tried it many times.


A new one is less than $100.

 

Just an update been putting premium gas in and it seems to have mostly gone away.

 

Hey, thanks a million for getting back, much appreciated. I think the Renix ECU will try to keep advancing the spark timing, until the knock sensor tells it to knock that off, and retard it until it's not pinging, (knocking with pre-detonation).

Normally I'd expect that worse, hot, under heavy throttle. Anyway glad premium works, there might be stuff on the knock sensor here, https://www.cherokeeforum.com/f51/he...ix-links-1397/

Also I heard "lore", that if you rap on a working knock sensor with the engine running, you will hear a difference.

 

Quote: "Also I heard "lore", that if you rap on a working knock sensor with the engine running, you will hear a difference."

A piston will come shooting out of the block, thereby making the engine sound different.

 

That's three knocks on the sensor. Knock twice and your rear main blows.

 

A knock senor is just a tiny microphone - on the side of the block.
The timing advance system is always seeking the best timing situation, just below spark knock.
The computer keeps advancing timing 2 or 3 degrees at a time each revolution - till the knock sensor detects a knock - detonation.
Then the computer (oops, too much) drops timing about 10-12 degrees. Then it advances again till the next knock. That way it's able to continually seek the highest advance no matter how other conditions change - load, speed, TPS, O2 etc.

Cold it just goes to a predetermined value.

To test, simply tap on the sensor when warm, timing will change, you'll hear the speed change momentarily. If the knock sensor wasn't working you'd have lots of constant pinging - you'd know it. The advance would go way above 60 degrees - rattling like crazy.

BTW - just the opposite - something rattling, like a loose bracket somewhere can be "heard" as a knock causing it to really retard - causing low power and poor mileage. More than 1 alternator or power steering bracket has caused all kinds of Hell.
'

Symptom still sounds like an exhaust leak.