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low compression one cylinder

A: You could be leaking air on your valves

Q: Low compression on one cylinder blowing inside the valve cover?
I have an 89 Mitsubishi Mighty Max and recently have had a cylinder not fire. The truck now runs on three cylinders but on the dead cylinder I still get spark and fuel. The truck is carbureted so I know it is not a clogged injector, but I had a feeling there is buildup on the intake valve. The valves are moving and after I sprayed about a can of carb cleaner, the truck runs a little smoother, but when I disconnect the dead cylinder, there is no change. This tells me that the cylinder still is not better. I would like to here some ideas if any body has some. Thanks.

A: For it to be pressuring the valve cover it would have to be rings on that cylinder

Q: How hard is it to fix low compression?
I am looking to buy a truck and the one I am looking at says:
“Runs and drives but needs engine work(#4 & #8 Cylinders have low compression) “

Just curious if this is an easy fix, really hard fix, etc. Looking for a price range/skill range of best and worst case scenarios.

Thank ya very much :)

A: Only way to fix that is to rebuild the engine. No can of snake oil is going to restore compression.

so yes, it can be quite hard.

It could be piston rings worn out, or it could be a valve problem.

you could do a cylinder leakdown test to determine which it is.

my advice- don’t buy it unless you want to totally rebuild the engine.

Q: Cylinder 2 and 4 low compression for My Toyota Celica 2000 GT-S?
I have been trying to fix this problem but couldnt figure it out. I did a compression test and cylinder 2 adn 4 were low on compression, one was 90 and one was 120. The codes im getting is that cylinder 2 and 4 are misfiring or sometimes it woudl say random misfire . Can someone please tell me whats the best way to fix this problem. Thanks i would really appreciate it.
The other 2 cylinders are fine the compression was 180 but only numebr 2 and 4 were low one was 90 and one was 120. I really want to fix this and im gettign confused can someone please help me. I would really appreciate it.

A: You didn’t state what your readings were on the other cylinders. We need to know those to help you. If compression is less than 75% of your highest cylinder, then you have a problem. At this point, you should do a leak down test.
In the May 2009 issue of my (free) newsletter on my site, I describe how to do a leak down test, and what the results will tell you. A leak down test can tell you if the problem lies with your intake valves, exhaust valves, head gasket, or piston/cylinder walls.

I also show how to convert a compression tester into a leak down tester, but you need an air compressor as a source of air.

Q: What is the Factory Compression Lbs. for a 1983 Honda V65?
I have a 1983 Honda V65 Magna that I’m working on for a friend. High Compression is 90 Lbs. one cylinder down to a low of 40 Lbs on the lowest cylinder. Does anyone know what the stock rating is for this bike. It runs but barely….. Thanks!

A: This link may give you your answer.

http://www.bikez.com/motorcycles/honda_vf_1100_c_-_v65_magna_1983.php

Q: dealership said my 03 aviator needs 2 new cylinder heads?
only 60,000 miles. low compression on cylinder 6 and 7. They gave me some read out paper with percentages cyl 6=14% cyl 7=5% and also cyl 3= 4%. Does that mean that cylinder 3 is about ready to have to be replaced as well? My car drives fine except for the occasional misfire when setting at a red light. Can it be anything else? From other peoples complaints it sounds like it could be my coils. Could it be something else when codes PO306 and PO316 appear? One more question the dealer did not even address code PO460 (fuel level sensor malfunction) My fuel level sensor stopped working a year ago when I ran out of gas. Any answers or suggestions would be so helpful. Thank you

A: Low compression has nothing to do with coils.
P0306 and p0316 are both misfire codes. Could be low compression, could be faulty coil. The “codes” are an aid in locating a problem, not an absolute answer. Cylinders do not get replaced.
Ok so the dealer did not address P0460 so your question is?
Dealer is proposing an expensive repair. You know just enough to be dangerous. My thought is get a trusted second opinion on this proposed major repair. Locate a garage below

Q: compression?
i have a question hopefully you guys/gals can help:

if an engine has one “dead” cylinder or low compression, when you remove the injector harness (cut fuel supply) or remove spark plug wire, should’nt the idle get rougher either ways. or no?

t.i.a!

A: well unless the cylinder is physically not there there will be some amount of compression unlike answer above stated. But if the cylinder is totally dead there will be no difference, but since it is probably not totally dead it is just misfiring a lot or loss of power on that cylinder it will make a difference, and have a much rougher idle

Q: Does any one out there know what the design compression is for a johnson 1987 200 Hp outboard motor should be?
I’ve herd that they smoke heavily when compression is low. I have recently purchased a project boat and have not run the motor yet but have done a compression test. the range is 90- 100 psi on all but one cylinder with a compression of 80psi.
any input is much appreciated! Thanks!

A: New out of the box is more like 140 psi, but after break in it’s more like 120 psi. It’s not hard to remove the dead and do a visual inspection, but sometimes you need to look at the side of the piston that rubs against the intake/exhaust ports. There is a cover over this on the side of the block. Repairing often involves honing or boring the cylinder, that requires dis-assembly.

Q: 1989 mercedes 190e 2.6 runs smooth but idles rough?
new plugs put in. one cylinder has low compression
any ideas thanks

A: most likely you have a burnt out exhaust valve on that cylinder, however before you pull the head off try a decarbonizing treatment [bg products has a good system for doing this]
then preform a leakdown test on the “low cylinder” air escaping from tail pipe= exhaust valve, intake manifold=intake valve, oil fill /dipstick tube=rings
note a good cylinder will leak less than 20 percent of the meetered air blown into it and is to have the piston at top dead center with the valves closed while being tested

Q: Low compression but no burnt oil?
I have a 91 mustang with a 2.3 turbo swaped from a 88 turbo coupe thunderbird. One cylinder was not firing so I did a compression test and the results from the dead cylinder was 30 psi, one was 119psi and the other two around 90 psi. Car will start and idle (idles lil rough do to the one cylinder being down) very lacking in power while driving though fairly smooth in upper RPMS and under boost with power picking up a good bit.

However the car does not seem to smoke at all and doesnt seem to burn much oil. Could bad valve seals alone cause that big of drop in the one cylinder or would piston rings be more likely or another cause? I just dont want to tear the whole thing down to change piston rings to find out it was sumtin more simple up top in the head.

A: not valve seals but the valves themselves. Remove the heads and inspect

Q: why turbo cars use low compression?
I could never figure this one out, most turbo gasoline cars use lower compression setups, but wouldn’t it be just as effective for a engine to run 15psi of boost with 9.5/1 compression compared to 20psi with 8.5/1 compression, If fact wouldn’t the higher compression has the advantage, due to the fact of turbo lag and being a lot safer on the turbo. Also is there a mechaincal advatage to having lower compression. I figured if the pressure in side the cylinders at the point of ignition on the example I stated recently are equal to one another then why is lower compression set up more popular?

A: Consider the fact that with a turbo, it is pulling more air and fuel into the cylinder then it would normally have. Basically you are stuffing a cylinder (just as an example) with 500cc’s of an air fuel mixture into a space that normally holds 350cc’s. Something has got to give to compensate for the extra pressure and stress on the block, usually it is the side of the block. By lowering the compression and raising the boost psi, you make nearly the same amount of power as a high compression rating and less boost. You also lessen the amount of stress you put on the block. Since nobody like to crack their block in half. Also as a side note the timing is retarded to prevent any for of premature detination, not compression.

Q: 1986 Suzuki Samurai question?
My almost 17 year old son recently purchased a used (on CraigsList) 1986 Suzuki Samurai. He has been now told by the mechanic there is something ‘very wrong’ and he’d need to open up the engine to diagnose (he used words like the second cylinder has low compression, it could be a rod, could be a piston). The immediate issues is that it was overheating (all of a sudden) smoking from under the hood, the radiator fluid was leaking everywhere (though the guy could not find a hole and it may have been from the over flow thingy. It also sounds really loud, and the mechanic said it was something in the engine. It has also been a pretty hard vehicle to start up.

One option he suggested is that it might be more economical (rather than spend all that money on diagnosing) to get a new engine. The current car is 1.3 liter. My son had mentioned replacing it with a rebuilt 1.6 liter — but the mechanic was told by his engine guy that you can’t just swap one for one on this particular year. My son (with all the wisdom of being almost 17) KNOWS that he can swap it out, but mechanic said there would be issues with transmission, wiring everything.

My son is quite attached to this car, though it has never been running “stable” — meaning it seems like it is always something. He has made some investments in purchasing and lift kit (not installed) and new wheels and tires (now sitting in the garage waiting to be installed). We told him not to buy before it was running consistently, but oh well, it was his own money and a good lesson, but since he has spent as much in “after market” stuff as the car, I think he’d like to be able to use that stuff.

A few questions for the wise folks of Yahoo:

1. My son loves the car and he spent his own $$$ on it ($1400) do you think it makes sense to replace engine or fix?
2. If replace, can we swap a 1.6 liter?
3. Should we just cut our losses?
4. Other options to consider

A: Okay, here we go! Your son, in his infinite wisdom, has actually picked a pretty decent little vehicle to play with. In stock form it will get almost 30 MPG and run at highway speeds easily.
It seems by your description that the engine is toast. If you or him or someone you know and trust can do the rebuild without taking it to a professional it will save a ton of money. The parts to do a rebuild if you stay in stock form will run about $550 or so. There may be some machine work that will have to be done and the prices are very regional so I’m not even going to try.
The parts you need to do the job are not hard to find at all. Check your local car parts place and if no luck try TrailTough.com or roadless gear.com.
Hope this helped and good luck!

Q: What should I do with a dead cylinder?
Hi, I bought a Nissan Maxima (1994) few months ago and it was working all fine. The engine still starts up well however in idle mode it is like a shaker. The mechanic says that one out of six cylinder is dead and the compression is low. what do you suggest me to do? how long this can work?

A: You need major work, maybe even a new motor.

Q: 1999 Honda CRV – Piston # 2 non or low compression?
I took my car to change the timing belt, and now the mechanic is telling me that one of the valves was hit or something like that, so I need to change it. The car is running fine, but maybe the main question is how long the car is continue running with only 3 cylinders? or what you recomend? Thanks

A: If one of the valves was hit (it’s called an interference cylinder head) then the vehicle should NOT be running fine. If it is running fine get a second opinion.

Q: Ford Focus Low Compression?
Test one: Cylinder 1= 190 Cylinder 2=210 Cylinder 3=205 Cylinder 4=210
Test two: Cylinder 1= 155 Cylinder 2=210 Cylinder 3=210 Cylinder 4=210
Checked 1 third time still 155

Is this a blown head gasket or piston rings or worn cam lobes
Any ideas?
if my tool isn’t working then i think everyone else’s might be broke also
Source Cited

http://forums.focaljet.com/forced-induction-nitrous/468518-compression-test-results.html

A: It’s a bad valve. You need to take cylinder head off and get the valves reground and maybe replace one or two, and get head resurfaced.

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