2.5 engine tick or knock. Coming and going. Lifters seem ok (Page 1/3)
cebix JAN 13, 04:27 PM
'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?
cebix JAN 15, 08:20 AM
Anyone? I've been reading about piston slap, could this be a possibility?
Dennis LaGrua JAN 15, 09:44 AM

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.

------------------
" 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 "

cebix JAN 15, 01:17 PM

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.
Dennis LaGrua JAN 18, 09:18 AM

quote
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 "

cebix JAN 18, 03:02 PM

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.
Patrick JAN 18, 04:18 PM

quote
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!
cebix JAN 18, 04:34 PM

quote
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.
Neils88 JAN 19, 04:17 PM
Make sure you check for any electrical arcing. It can sound just like a faulty lifter. A mechanics stethoscope is helpful tracking down noises.
cebix JAN 20, 02:56 PM

quote
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?