BlackPearl808

Howzit?
So after replacing my fuel filter (I suspected I got some bad gas here in Hawaii) I noticed that my loud 89 Toyota Pickup got even louder.
At first I thought it was an exhaust leak (I recently found out that my exhaust manifold is warped when I replaced the gasket) but I can't
feel any exhaust coming from the anywhere.
The sound only happens under load and gets louder the more gas you give it. It doesn't do it while idling. I noticed a drop in MPG because
I drove it for about 250 miles this past weekend and had to fill up earlier than usual
Some history:
-odometer has 162K but according to the internet vin search, probably waaaaaay more
-the plugs & wires (NGK), cap, filter have been replaced in the last couple of years.
-I adjusted the valves 6 months ago (thanks yotatech)
-the previous owner said he replaced the chain&guide when he got the truck..that was about 20K miles ago
-PO also did away with the cat-con
My question:
Is it possible that I messed up the knock sensor because when I had to take it off to get the fuel filter off and a bunch of gas
spurted out (I relieved the pressure small kine) in the process?
I checked the knock sensor and it looks ok but the plug that goes into it is small kine loose after I unplugged it..is that buggah supposed to be
on there tight tight? the CEL never came on
Also, if it's not that, what else can it be?

Mahalo for reading

BlackPearl808

Checked the timing, it was way off, about 12* TDC instead of 5* BTDC. Made it sound waaaaay better.
I also found a small exhaust leak at the EGR fronting the exhaust manifold. Could that make that loud sound?
I only really hear it once the truck has a load and not so much when I'm revving the engine at idle.
Does that matter with the sound?
Also, should I check the valve gap since I corrected the timing? I did it about 6 months ago

BlackPearl808

I'm thinking it's an exhaust leak. After some research guys are saying that a warped manifold might be the culprit. Going to have it resurfaced and
then putting on a Remflex gasket. TBC..

BlackPearl808

I took off the exhaust manifold and I didn't see any obvious leaks. I heard (but didn't feel) what sounded like an exhaust leak coming out of
cylinder 2 before I took it off. I suspect something's up though cause check out the manifold coming out of that cylinder..what could be causing that?
#3 and #4 look like #1

I checked the spark plug and it seemed ok. also, I checked the warpage of the manifold and it's probably around .7mm (my biggest feeler gauge was .633)
there is some indication that there might be a leak at #2 (around 11 o'clock) so I will go ahead and resurface the manifold for $60 and wait for my
new gasket. Once I do that I will try and adjust the valves and since nobody is reading this,

RASALIBRE

Are you sure you're not hearing pinging? If the noise is still there after you get the exhaust manifold decked and installed, I'd try higher octane gas. If that eliminates or reduces the sound then you know for sure it's pinging. At that point I'd start chasing down vac leaks, ohming out all efi and ignition sensors hot and cold, (start with cleaning the throttle body and a TPS check/adjustment) check for faulty/sticking/clogged injectors, faulty fuel pump or fuel pump wiring.

BlackPearl808

Thanks for the reply.
When I took the manifold to my gearhead friend and asked him about the suspect port for cylinder 2, he found a crack so I went to the junkyard instead and got a old new manifold.
What a difference! The sound is gone, I feel a slight increase in overall power (I never used to go to 5th gear up this hill to town) but now there is a hesitation (truck jerks sometimes
when accelerating. I hope that new plugs will solve this as I did notice that plug 2 was caked with white build up that I think is a result of the leak and the advanced timing (that I corrected)
making the mix super rich. I wonder how long the ECU takes to readjust the mix after I made all these changes..

RASALIBRE

Right on! Congratulations! You can pull the efi fuse and or disconnect the battery to reset/clear the ecu's learned fuel trim. Leave em pulled/disconnected for at least thirty seconds. The ecu will readjust/relearn fuel trims to the new or changed components in something like three to five key cycles.

BlackPearl808

Cool, I'll try disconnecting the battery. Before I adjusted the timing, I set the idle to 800 but I did so by adjusting the throttle stop screw which I learned from 4crawler.com is NOT the way to do it.
For some reason the adjustment screw was stuck. I will undo that, re-adjust the timing then re-check the valve clearances. Hopefully, that will take care of the hesitation, but just in case, I ordered brand spanking new silicone vacuum hoses from LCE.

cbh148

Any updates with this BP808?

I've got a '94 XtraCab 4x4 22RE 5-speed that, for the last 1.5 years since buying it, has been making the same exact sound that I believe you're describing.

I too have replaced the exhaust manifold gasket as well as the 2 donut gaskets between the manifold and the downpipe but it made no difference because the ticking/rattling under load is still there.

I advanced my ignition timing to try to milk any extra power out of this mofo, which had me thinking I might've gone too far and caused this sound since perhaps it's the sound of detonation, but then I remembered that it was making the sound prior to me advancing the ignition timing from the stock position, so that must not be it.

My plastic timing chain guide broke not long ago and I caught it before any catastrophic damage was done, and decided to just go ahead and pull the engine to make it easier to properly clean everything during the installation of the new chain and metal guides, as well as a new chain cover, oil pump, and clutch/flywheel and properly resealing the oil pan. I deleted all of my emissions components while the engine was out just in case they were causing the sound (EGR, PAIR), yet after putting the engine back in after this serious tune-up service, it still makes the sound.

I've got an LCE catback exhaust with a flex-pipe replacing the catalytic converter because I thought the cat could've been broken inside and causing the sound, but deleting the cat made no difference to that damn ticking/rattling under load.

Been considering getting the LCE header just in case this sound is an exhaust leak that isn't causing a big black mess at the point of leakage like I assumed most exhaust leaks would do. So that header would be primarily for stopping this sound, with any minor 0.5 HP gains being a secondary little bonus at best.

BlackPearl808

cbh148
there was a small crack in the exhaust manifold that I discovered because I took it off. I was going to get it machined flat as there was a slight warpage. it was at spec limit but I figured I'd try anyways cause it was driving me nuts. I was doing the plastic tube trick to the ear to listen for any weird sounds and only could hear a very slight little rattle when I put it near the #2 exhaust. the problem was that I could only hear the slight rattling sound during idle and it wasn't when the truck was going that it really made the noise. my friend saw the tiny crack then it was off to the junkyard to get another manifold. bonus because it had an intact heat shield.
hope that helps and good luck!