I just put in a low-mile rebuilt engine and I am hearing some knock, but I am not sure if it is the engine or something else rattling during certain loads on the engine.

I hear it when I start to take off and also when there is a light load on the engine - like when the auto tranny is shifting into the next gear or shifting down when I decelerate.

Also, what does you oil pressure normally read when in gear (auto)? Mine gets down to just above the red line once it is warmed up.

If this engine is bad, then it's 3.4 time!

Thanks in advance!

If you've ever heard a little fuel knock, that's what an early rod knock sounds like. Could be a little out of time..

This one almost sounds like an exhaust leak - except that it does not happen at WOT.

Saxman - Just noticed your new avatar, is that special for this thread

Cheers

GAH!!!! Hope that 'new' engine is ok!

oh yeah, and

That avatar turns my stomach!

OK, I'll take off the "battered rod" avatar, Rumor. This avatar is more appropriate - since my kid wants to come out and help now

[This message has been edited by Saxman (edited 03-17-2008).]

I hear it when I start to take off and also when there is a light load on the engine.

Spark knock / timing and don't trust the harmonic balancer.


What is a Waht?

Ed

quote Originally posted by Fino: What is a Waht? Ed

one joule of energy per second?

It sounds like a lifter tick, or an exhaust leak. Most prominantly at light to no load driving conditions at all speeds. I found it was a little quieter when I would either let it idle, or if I was on it a bit. It turned into a full blown rod knock after 2 weeks. I didn't even know it was a rod knock till then. But I did replace the lifters after the first week, thinking they were the tick I was hearing. A week later it got ugly, I barely made it to work, then barely made it home, I drove about 40 miles with a severe rod knock.

Have you checked the timing now that you have it running?

The first thing to check is the lifters. If they are not roller tipped they will produce a light knock if they are too loose. On a rebuild, the lifters are far more likely to be out of adjustment than a rod, unless of course you broke it in at WOT

It is a PITA to have to re-check your lifters, but, I think it sounds necessary. A rod would likely sound more obnoxious as you rev up.

Arn

the oil is a good place to look also. unscrew the oil filter, then pour its contents out and look for the shimmer of ground up bearings.

stethescope is another fine tool. get the butt in the air, then crawl under there, and put a stethescope to the oil pan. the knock will be MUCH more noticable. and will sound VERY different from a lifter/rocker noise, which is easier to here from the valve covers.

quote Originally posted by Jake_Dragon: Have you checked the timing now that you have it running?

Not yet, but the timing guns is out there. I'll hit it with the gun soon. This will be my first time using a timing gun. (Yup - I'm lame...)

NO This is a Waht:
To set initial timing, you MUST put the ECM into diagnostic mode. This means the ECM provides zero advance so you can use your timing light to set base. This is done by shorting pins A & B together on the ALDL connector. 8 degrees base.

Or maybe it really is "one joule of energy per second"

Cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg.
Ed

[This message has been edited by Fino (edited 03-17-2008).]

quote Originally posted by Fino: NO This is a Waht: Or maybe it really is "one joule of energy per second" Cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg. Ed

Saxman this guy might really be in Merry-Land
If you cant get your hands on a stethascope, use the wooden stick. It'll work the same exact way. Rod knock will be deep in the block, rockers or lifters will be inside the valvecovers.
Joe

[This message has been edited by josef644 (edited 03-17-2008).]

I use a 3' length of surgical tubing. Works the same way and gets into those tight spaces.

Arn

quote Originally posted by Arns85GT: I use a 3' length of surgical tubing. Works the same way and gets into those tight spaces. Arn

I guess the extra vacuum tubing will do, too - huh?

It is very hard to diagnose noise over the Internet maybe You Tube? Anyway I try to focus on the easy stuff first before getting into tearing the engine down.

When you say, “I start to take off and also when there is a light load on the engine” the first thing I think of is timing. Now you also say later “except that it does not happen at WOT” normally I would think you would have spark knock at WOT but if the engine is noisy you might not hear it as easy as tipping into the throttle.

Spark knock is almost like a crackle/buzz fast like every cylinder. Rod or rocker much slower only one cylinder. Rod heaver, rocker lighter noise …taping sound. As said before rod sound under the car. Rocker sound valve covers.


I hope for your sake it is just timing.
Ed

Me, too, Ed.

I guess the first thing I should tackle is the air hissing under the intake. Once I fix that, my idle will probably change. Then I can set the timing properly.

More to come soon-

quote Originally posted by Saxman: Me, too, Ed. I guess the first thing I should tackle is the air hissing under the intake. Once I fix that, my idle will probably change. Then I can set the timing properly. More to come soon-

hissing under the intake
Does not sound good ...lean engine spark knock.

Ed

I just did the leak test via DodgeRunner:

quote Originally posted by Dodgerunner: Most likely. The other way to test is put all the hoses on. Pull the air duct from the TB. Put your finger over the idle air port in the bottom of the TB. If the engine dies it's most likely not vac leaks. If it keeps running like it is then it is a vac leak. Have you check the EGR tube? Is it loose if you wiggle it or solid... Also is your throttle stop screw untouched, IE the cap is still on it or no one has messed with it...

Mine didn't die when I blocked the idle air port. It just slowed to a normal idle speed. I guess it's time to check the EGR tube, then pull the upper intake, if needed. What a pain in the ...

It sounds like the Idle Air Port is where all the hissing sound is coming from.

[This message has been edited by Saxman (edited 03-17-2008).]

A rod knock may be imperceptible at idle, but get louder as RPM's increase. At even higher RPM's (above where it's loud) an early stage rod knock may seem to go away.

quote Originally posted by pswayne: A rod knock may be imperceptible at idle, but get louder as RPM's increase. At even higher RPM's (above where it's loud) an early stage rod knock may seem to go away.

This does seem to go away, but comes back just when the load is light. It doesn't get louder as RPMs increase, so I'm still hoping the vac leak and timing are the culprit.

I get to go out and play in the garage after dinner...

a bad wrist pin will cause the symptom you describe.
Just my $0.03
Dave

quote Originally posted by bmwguru: a bad wrist pin will cause the symptom you describe. Just my $0.03 Dave

Just like an import mechanic over charging for everything. Just my $0.02

Saxman, change that oil and filter, get that old oil outta there pronto. Maybe even some straight SAE 30 till you get this all worked out. Oil and a new filter is cheap compared to rod bearings. If this was mine I wouldn't even consider starting it again untill I knew what was in the oil pan. I think I read that you were running the old whatever that was in there? Oil pressure light coming on isn't a good sign.
Joe

[This message has been edited by josef644 (edited 03-17-2008).]

Alright - I'll pull the oil. That would be the easiest first step to make, anyway.

I dread trying to get under that intake again - especially when the engine is back in the car. I'm too damn tall to lean down over that low engine too long.

I'll have to listen through a tube/stethescope to see if that is where the air is hissing under there.

I need to give it a break for tonight. I just don't have the patience after spending every free hour this month getting it all back in. Geez!!!

It's beer O'clock...

What weight cha gonna put in it Saxman?
Joe

I'm wondering how much insurance money I can get for it at this point...

I'm off to drink a beer and call it a night. I'll tackle this bastard tomorrow night.

My wife just got back from the gym and she is looking good. I might as well play with SOMETHING that works!

quote Originally posted by Jake_Dragon: Just like an import mechanic over charging for everything. Just my $0.02

I used to work for Wal~Mart so I'll under cut you and give you my $0.01 and sell it in a bag of 10. Of course my is made in China and is painted with lead and will break after a week.

Jim

[This message has been edited by jimbolaya (edited 03-18-2008).]

quote Originally posted by Jake_Dragon: Just like an import mechanic over charging for everything. Just my $0.02

glad somebody got my joke.

Sax, I don't talk on the phone much, but I'll have Joey text you my shop's number...it forwards to my cell after hours.
Dave

ps...SAE 30 might be a little too thick for MD this time of year...the most I would go is 20w50

[This message has been edited by bmwguru (edited 03-17-2008).]

quote Originally posted by bmwguru: glad somebody got my joke. Sax, I don't talk on the phone much, but I'll have Joey text you my shop's number...it forwards to my cell after hours. Dave ps...SAE 30 might be a little too thick for MD this time of year...the most I would go is 20w50

I agree, I forgot where he was. I'm in Texas. It was 84 here today, 90 miles north of Houston
Joe

I'm about to drain the oil

Question - would a bad EGR tube cause the vacuum/hissing sound? Mine looks good. Just wondering if I should even remove it.

I have the feeling that the vacuum sound is coming from another part under the intake. I don't think the EGR would cause a vac leak, but I'm not sure.

the stock Fiero intake Hisses as-is
but, yes - a broken EGR tube could hiss also.

It could be the rubber tube for the IAC right behind the throttle body.