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2.5 engine tick or knock. Coming and going. Lifters seem ok by cebix
Started on: 01-13-2021 04:27 PM
Replies: 13 (131 views)
Last post by: Spoon on 01-20-2021 07:58 PM
cebix
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Report this Post01-13-2021 04:27 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post
'85 duke auto w/AC. Engine rebuilt a year and a half ago.

Amidst other problems this car has there seems to have occured something more severe this time.

After doing about 200 miles straight I noticed a slight knock coming and going from the engine. It started off quiet with low rpm, disappeared for a few seconds at higher revs and came back with lower, etc. More like ticking actually than knocking. The next day I started it cold and the knock was HUGE not going away. Getting worse with higher rpm. After about a minute of running it disappeared altogether. Drove about 5 miles and the ticking/knocking was coming and going.

My immediate guess was one of the lifters has gone bad. Those were all new from Enginetech. However my mechanic got around to them and said they were fine, not one is soft and they are all good. Still don't have a diagnosis and looking for clues.

What else can cause such an issue?
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cebix
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Report this Post01-15-2021 08:20 AM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post
Anyone? I've been reading about piston slap, could this be a possibility?
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Dennis LaGrua
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Report this Post01-15-2021 09:44 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by cebix:

Anyone? I've been reading about piston slap, could this be a possibility?

Piston slap usually occurs more often when the engine is cold. If the sound is more a tick then its likely a lifter or loose rocker arm.. If the sound comes and goes then my guess would be the valvetrain. Have you checked for clearance/adjustment ? Mark harmonic balancer with a chalk mark. Rotate 1/4 turn check by trying to lift each pushrod with your fingers for any looseness. Rotate 1/4 turn try again and keep doing this for two complete rotations. If you can rattle any pushrod by feeling excessive up-down clearance, there is your problem.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
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cebix
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Report this Post01-15-2021 01:17 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Dennis LaGrua:

Piston slap usually occurs more often when the engine is cold. If the sound is more a tick then its likely a lifter or loose rocker arm.. If the sound comes and goes then my guess would be the valvetrain. Have you checked for clearance/adjustment ? Mark harmonic balancer with a chalk mark. Rotate 1/4 turn check by trying to lift each pushrod with your fingers for any looseness. Rotate 1/4 turn try again and keep doing this for two complete rotations. If you can rattle any pushrod by feeling excessive up-down clearance, there is your problem.



Yeah when cold it was ticking/knocking very loud, like obnoxiously loud - something I heard on another engine when a valve burned out. However with that engine with revs it became happy. The Fiero with revs was ticking/knocking louder. A minute after running cold it just disappeared but came back quietly when hot under different conditions and went out again.
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Dennis LaGrua
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Report this Post01-18-2021 09:18 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by cebix:


Yeah when cold it was ticking/knocking very loud, like obnoxiously loud - something I heard on another engine when a valve burned out. However with that engine with revs it became happy. The Fiero with revs was ticking/knocking louder. A minute after running cold it just disappeared but came back quietly when hot under different conditions and went out again.


Its not going to get fixed by guessing. You will need to go through the checks to diagnose the problem.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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cebix
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Report this Post01-18-2021 03:02 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Dennis LaGrua:


Its not going to get fixed by guessing. You will need to go through the checks to diagnose the problem.



Yes, working on it with my mechanic, was just looking for some ideas since he ruled out the hydraulic lifters. Maybe these engines have something in common that cause this, that's why the topic came about.
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Patrick
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Report this Post01-18-2021 04:18 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by cebix:

...working on it with my mechanic, was just looking for some ideas since he ruled out the hydraulic lifters.


Just how did he rule them out?

Why don't you shoot some video with your phone and upload it to YouTube for us to see. We're more interested in the audio, so get the phone in close to various parts of the engine while it's running and ticking/knocking. Just be careful around moving belts and pulleys!
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cebix
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Report this Post01-18-2021 04:34 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by Patrick:

Just how did he rule them out?

Why don't you shoot some video with your phone and upload it to YouTube for us to see. We're more interested in the audio, so get the phone in close to various parts of the engine while it's running and ticking/knocking. Just be careful around moving belts and pulleys!


Well he said none are collapsed or soft and he's 100% sure it's not the lifters. Shooting a video is gonna be troublesome now since the car is ~200 miles away. I can say however that from youtube videos it sounds like those bad lifter and piston slap videos. Definitely not a rod or crank bearing sound, not that metallic kind. Wish I recorded a video when it started first but didn't think the diagnosis would take this long.
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Neils88
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Report this Post01-19-2021 04:17 PM Click Here to See the Profile for Neils88Click Here to Email Neils88Send a Private Message to Neils88Edit/Delete MessageReply w/QuoteDirect Link to This Post
Make sure you check for any electrical arcing. It can sound just like a faulty lifter. A mechanics stethoscope is helpful tracking down noises.
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cebix
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Report this Post01-20-2021 02:56 PM Click Here to See the Profile for cebixSend a Private Message to cebixEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by Neils88:

Make sure you check for any electrical arcing. It can sound just like a faulty lifter. A mechanics stethoscope is helpful tracking down noises.


You mean like high voltage arcing, like a spark plug wire? Not low voltage stuff?
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cvxjet
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Report this Post01-20-2021 03:54 PM Click Here to See the Profile for cvxjetClick Here to Email cvxjetSend a Private Message to cvxjetEdit/Delete MessageReply w/QuoteDirect Link to This Post
You can make your own "Stethoscope" with a piece of 1/2" Heater hose....

Just another possibility; On my CVX-20 Jet BOAT 460 engine I had a loud ticking sound- like two wrenches clanging together...Turned out to be an exhaust leak thru one of the smog pump ports at the end of the head- in the enclosed engine compartment it sounded mechanical, not like a typical exhaust leak.

Although this applies to my BOAT with a completely enclosed engine compartment, I have never heard what an exhaust leak may sound like on a Fiero...especially considering where it may be located on the engine....
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edfiero
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Report this Post01-20-2021 04:36 PM Click Here to See the Profile for edfieroClick Here to Email edfieroSend a Private Message to edfieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
A leaking exhaust gasket can also make a ticking sound and is an easy fix compared to the other things that might make similar noises.

That said, years ago, the piston ring land let go on my 2.5, that was making a really loud knocking sound.
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Patrick
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Report this Post01-20-2021 06:33 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes, a cracked exhaust manifold can certainly make some strange "ticking" noises, especially if the crack is located next to an individual port. And it can come and go as well, depending on metal expansion/contraction from heat.

[This message has been edited by Patrick (edited 01-20-2021).]

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Spoon
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Report this Post01-20-2021 07:58 PM Click Here to See the Profile for SpoonSend a Private Message to SpoonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Sorry for your situation. If the knock is as loud as you described and it got better without doing some work, I doubt it's a rod knock. With the exception of someone adding 90 wt gear oil to the crankcase I've never heard of one getting better on its own. Excessive rod bearing clearance is not like a lifter tap where the slack can be taken up with oil pressure. Have you checked your oil pressure with a real pressure gauge connected to the engine? Let us know.

On the other hand I would be curious why a 2 yr old engine rebuild would develop an engine knock. Just the words "engine rebuild" leaves a lot of open areas such as what was included. Even an honest mechanic may have to depend on a trustworthy machine shop to do some of the work. My neighbor had a valve job done and still had problems afterwards. I took a look and discovered a valve job could miraculously be done without removing the head from the block and the new head gasket came with the factory color already on it. Lesson learned it doesn't hurt to ask for the old parts even if you're not sure what you're looking at.

Keep us posted. Maybe it's just a cracked exhaust manifold. They can expand and contract due to temperature changes and make various sounds depending on the size of the fracture.

Spoon

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