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'03 Chevy Malibu Cylinder Compression

My 2003 Chevy Malibu recently, out of nowhere, starting idling really hard. It shakes and jumps quite a bit when it idles, much like a car creeps when it’s about to run out of gas. It drives fine at speeds over about 10-15 mph, but then when it slows down it gets shaky and bumpy.

I took it into a shop and was told that cylinder 4 has no compression. He wasn’t sure specifically where the problem is, and to find out would require some expensive digging. The fix he quoted me would be about $1500-$2000, not knowing if it’s the gaskets, head bolt, or what. The other option is to change out the motor completely.

I’m wondering if this sounds right. I’ve never heard a mechanic say that it would cost over $500 just to pin down the specific problem, but he came highly recommended and seems to care about being honest. I’m also wondering if a car with a KBB private sale value of $2500 is worth this kind of money, considering that it only has 96,000 miles on it. Can I get 3-5 years out of this kind of investment?

Anything helps, and I can provide more information if needed.

Thanks!

If they determined that cylinder 4 has no compression, a compression test had to be performed.

The next step would be to perform a leak-down test on cylinder 4 to determine why it’s low on compression.

Tester

If the cylinder has zero compression that usually points to a valve problem in the cylinder head.

Your first step should be to get the car away from that shop. It does NOT require expensive digging to diagnose this problem. It can easily be diagnosed with a compression or leakdown test and the only thing requiring removal is the spark plugs.

The logic they’re using about tearing an engine apart to determine damage is just as misguided as the often used one about having to replace a broken timing belt to determine engine damage.

Find another shop that understands what a basic compression or leakdown test is.

@aeschill

It’s disappointing, really

The shop probably hooked up a scanner and realized #4 cylinder is misfiring

Then they obviously performed a dry compression test, and #4 had 0 compression

But that $1500 estimate to diagnose seems to indicate they don’t know how to efficiently proceed

As said above, a leakdown test wouldn’t take very long, and wouldn’t cost a lot

Are you sure the shop hasn’t already performed a leakdown test?

If they haven’t done one, and don’t plan on doing one, get your car out of there

Agreed that a leak down test is needed next, not an estimate for a used engine.

Yosemite

Leakdown test it is. Thank you everyone!

@aeschill

Please keep us informed about your car’s situation and/or progress

What am I looking for in the leakdwon test?

The leakdown test will tell you if the loss of compression is past the piston rings, an intake valve, or an exhaust valve; or a combination of all 3.
The odds of this being related to pistons or rings are extremely slim as this problem surfaced suddenly out of nowhere.
Coming on suddenly generally points to a valve problem in the cylinder head.

Generally speaking, if a valve sticks in a guide, a valve seat drops, a valve bends or distorts, etc there will usually be some noise associated with it; a ticking, rattling, or knocking all depending.

This is all predicated on the “no compression” as meaning zero. Low compression, not low, could point things in a slightly different direction.

I’m getting a second opinion tomorrow morning, and I asked for a leakdown test when he does it. I’m not going to say anything about the first opinion until I hear what he has to say.