# Low Compression one cylinder

**URL:** <https://community.cartalk.com/t/low-compression-one-cylinder/34958>\
**Category:** Maintenance/Repairs\
**Tags:** suburban, gmc\
**Created:** [August 12, 2009, 6:19pm UTC](https://community.cartalk.com/t/low-compression-one-cylinder/34958 "2009-08-12T18:19:33Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![hwyrovr](https://avatars.discourse-cdn.com/v4/letter/h/aeb1de/32.png) [@hwyrovr](https://community.cartalk.com/u/hwyrovr)\
**Post date:** [August 12, 2009, 6:19pm UTC](https://community.cartalk.com/t/low-compression-one-cylinder/34958/1 "2009-08-12T18:19:33Z")

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The Beast runs rough on initial start-up in the morning 1999, 192,000 mils, always well maintained, bought new in '00). Cylinder 4 has 70 lbs (others in the 120/140 range). Once the thing warms slithly it smooths out and seems to run fine. I am not in a position (financially - laid off - whine) to pay for a new engine or a new vehicle. Questions: What is the worst that can happen? Will the thing strand me somewhere by just stopping? Any thoughts would be appreicated.

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**Author:** ![bennyandthejets](https://avatars.discourse-cdn.com/v4/letter/b/b487fb/32.png) [@bennyandthejets](https://community.cartalk.com/u/bennyandthejets)\
**Post date:** [August 12, 2009, 6:29pm UTC](https://community.cartalk.com/t/low-compression-one-cylinder/34958/2 "2009-08-12T18:29:32Z")

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If it has hydraullic lifters, I’d suspect a bad lifter. Otherwise I don’t see a bad head gasket getting that much better as the engine warms up.

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**Author:** ![oldschool](https://avatars.discourse-cdn.com/v4/letter/o/e19adc/32.png) [@oldschool](https://community.cartalk.com/u/oldschool)\
**Post date:** [August 12, 2009, 9:41pm UTC](https://community.cartalk.com/t/low-compression-one-cylinder/34958/3 "2009-08-12T21:41:42Z")

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You are dealing with poor sealing between the valve face and the valve seat,its still sealing some (and the cylinder is still making some power). This is not a “leave me stranded type situation” is is a “no more boat towing” and “spend a little more on gas” siuation.

I don’t advise a valve job at the mileage you list but if your mechanic will warranty that the engine will not burn more oil (fat chance) or spin a rod bearing (why does this happen on high mileage valve jobs) go for a valve job with cam and lifters.

Or better yet find a totally different vehicle (one that someone just put a engine and trans and new brakes and new AC but cant afford the gas).

I don’t think your poor cold running is caused by the one cylinder at 70. If it was at 0 yes.

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**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\
**Post date:** [August 12, 2009, 10:13pm UTC](https://community.cartalk.com/t/low-compression-one-cylinder/34958/4 "2009-08-12T22:13:17Z")

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Squirt oil into the #4 cylinder before you do a compression check. If the numbers go higher, that shows the piston rings are leaking.  
Run the engine until hot, and recheck the compression (with and without the squirt of oil). Results?

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**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\
**Post date:** [August 12, 2009, 11:42pm UTC](https://community.cartalk.com/t/low-compression-one-cylinder/34958/5 "2009-08-12T23:42:55Z")

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All of those compression readings flat suck and it’s a sign the engine is worn out.  
A 140 is on the way out and 120 on down reeks.

Eventually low compression can get bad enough that the car will not start but that may be a ways down the road so I say drive it until it croaks.