Major Knocking and Terrible Idle

[Darkblitz9]

Okay, here's the deal. My Girlfriend owned a 95 Base with a 3.1L in it. Some small mods were done, the Cat had somehow melted so we just chopped it off and replaced it, and the muffler fell off so we replaced it with a Cherrybomb Extreem, very cool, but impertinent to this issue.
One day we hear a light knock, lick a ticking from the engine, obviously upper engine and verry unsettling. It made the noise about 3 times a second while idling and sped up when accelerating. We took it to a "trusted" Mechanic and his response:
"It's a common 3.1 knock, they all do it, nothing to worry about."
This guy didn't even hear it at first until we told him to pay attention.
2 Hours Later the Check oil and bettery lights flash right as the car stalls on the road.
Her fathers response (Because he swears up and down by his mechanic friend) "She was driving it too hard and whatever she did in those two hours caused it"
having the car sit for 1.3 hours and then taking a short trip to McDonalds must be a terrible strain on engines
Now the mechanic is doing his best to not look at it so since my girlfriend has a new car I get the Beretta. I'm ecstatic, I love this car and she never showed it any respect, but now I don't know what to do. the issue now is when starting it makes a horribly loud knock and the engine doesn't stay running unless being constantly revved up to at least 2k rpm, and even then it doesn't last long. it sounds like a busted lawnmower on it's last leg. I'm told it's a valve or several valves by her brother, who had to rebuild a Chevy Lumina's 3.1 (same engine it turns out) with the same problem. But now, he doesn't want to do the work and I'm desperate to drive my new (to me) 'Retta
Any answer as to what it may be? I have the time to work on it, but I need to know what it is before I go tearing the engine down.

[Money pit Beretta]

The 3.1 and the 3100 are not the same. A loud knock when it's cold is piston slap. If that knock goes away after it warms up it's normal. The knock up top should be the lifters.

[Money pit Beretta]

Oh man I'm sorry! Welcome to Bnet! Hope you get it fixed. And if you get some lifters make sure that they are rollers.

[1988GTU]

Maybe the cam has snapped and it is just barely running until all oil has drained to the crank case, in which it will seize and that will be that.

I advise removing the front valve cover and while it's running, look at the rockers to see if they all are moving.

[Luckymc420]

Anyway you can get a video of the sound? Could the MAP sensor have something to do with this. If the (edit: Cam) was not working on all cylinders you should be able to smell raw fuel. But I agree pull the cover off and take a gander. Also check to make sure you see oil coming out of the rockers.

Oh and you do have a 3100. And Welcome to the Boards.

[Asylum]

^^^ WHAT??^^^

The MAP has nothing to do with it and how in anyone's world the crank "can't work on all cylinders" is beyond me, let alone allowing the smell of raw fuel!!

3100's aren't known for the piston slap issue as much as the old 3.1's were, but it's possible, although it should in fact go away once warmed up.

As suggested, pull the valve cover and make sure everything is happy. It may have broken the camshaft.

How is the oil pressure?

It may not be worth spending alot of money on as labor can add up in a hurry, especially when a replacement engine is likely the easier, more cost effective and sensible option.

http://www.car-parts.com" onclick="window.open(this.href);return false; is a good locator or check with you local scrap yards for replacement engines.

There is a ton of swap information available. You didn't mention mileage, but it is certainly something you may want to consider.




And it sounds as if you need a new mechanic!

Good luck with it.

[Darkblitz9]

Well, it's the 3.1, not a 3100 and what I've been told is that it's probably a busted valve getting smacked by the piston to make that horrible noise and the way too much air+ the pistons not reaching their full stroke thats causing the engine to die out. I don't know, but I will take the suggestion of looking at the rocker arms while someone turns it over. And the audio I can get in a little while, I have to go get my phone and try to record it. I'll post it as a id with no video, just sound.

[Money pit Beretta]

My 3.1 never had slap and it had 213K on it. Not to say they never do. My 95's 3100 has a very loud slap until it warms up. In the summer it doesn't do it. I agree, a new engine would be better. Time for a 3400 swap?

[Luckymc420]

Good catch asylum. I ment to put Cam like was stated in the previous post. Also I would think the MAP sensor could retard and advance the timing and maybe it was starting to hydro lock the cylinders if they were not firing.

[Money pit Beretta]

Did someone put a 3.1 in there? If not it's a 3100. The parts are not the same, so make sure you tell the parts store what year you have.
A 3.1 intake looks like this. http://wot-tech.com/shop/all/gen-2-3-1- ... d_128.html" onclick="window.open(this.href);return false;
I'm sure your has 3100 SFI V6 on it and looks nothing like the 3.1 intake.
I'd bet money that it's the roller lifters that are bad. I have a friend here that had the same problem. It sounded like a rod knocking, but up near the valves.

[Luckymc420]

I had some lifters go bad and it would run but would die when put into gear. Just an FYi.

[Darkblitz9]

Sorry, mixed those up its a 3100 and the lifter problem sounds like it could be it Mone Pit. How did they solve th issue? Costs? at-home job or definitely mechanic? I have the time to do the job, I just don't know exactly what's going on yet. And yes, the knock sounds high enough to be at the valves but the more trusted mechanic who was initially worried to hell by the original knock believes it was either lifters or valves.

[3X00-Modified]

pull a valve cover off first and see if you can lift a rocker off the head of the valve spring... if you can then yes its lifters, if not then it may be something else.

[Money pit Beretta]

We all say get another engine because in the long run it would be better for you. With that said you can replace the lifters yourself. You will have to check into the costs of all the gaskets and the lifters. You will also need to unbolt the upper engine mount(you will need a way to support the engine). There is a great need for a Chilton's so that you have a better idea of how and what to do(also much needed torque specs). Someone to help, that knows how to work on cars would cut the work time down. It's not a huge job, but will take alot of time. Some guys here could bang it out in a few hours, but they know how to do it in their sleep. If you have the money take it to a shop. The high cost at the shop is because of labor. You can't just fish the lifters out with a tool like in the old days. The alt, PS pump, EGR, injectors/fuel rail and the coils need to be moved. Both intakes and valve covers must come off also. It would also be a good time to change the spark pulgs and wires. Not trying to put fear in you, these are just some of the things that you will need to do and think about. A good size tube of anti-seize would be a good idea(the bolts on the engine and spark plugs need it). I'll stop there.
Oh, that 3X00 guy is one of them that can do it in his sleep.

[3X00-Modified]

LOL, its only a LIMG equivalent job... I did that in my old storage garage out of a small toolbox and no power

Pics from when I did my lifters. (I took LS6 lifters and put the springs in my stock ones to keep up with my heavy valve springs and rough cam.)









spring comparison
stock on right LS6 on left.