Question about 1986 Toyota MR2

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I just bought this car and guy said needs valve job because of low compression in cylinders is this true or could it be something else?

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If the valves are bad so are the piston rings

Posted on Jul 17, 2010


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I have a 2000 chevy astro van with misfire code in cylinder 6. I was told that i have to replace the spider, fuel injectors. Could it be something else?

If, in fact, #6 fuel injector is faulty, you need only replace THAT one injector. If once you've replaced said injector and another check still shows #6 is misfiring, same code, then you have a faulty exhaust valve and are losing compression. Best to do a compression test on all cylinders with all spark plugs out before changing that injector. It could be good yet and you'd have changed it for naught. Compression test first, it's simple. I'f test shows low compression on #6 then the valve is bad and you'll have to pull the head off and d a valve job to re-seat the valve. Once re-seated, turn the face of the head gasket surface up flat and pour some alcohol into the head combustion chamber. If it doesn't leak out, your done. Put it back together.

Jul 13, 2017 | Cars & Trucks

1 Answer

What causes low compression

Weak or worn piston rings , needing a valve job , valves don't seating right . Timing chain or belt worn a bad head gasket , warped cylinder head . The way to find out would be to do a cylinder leak down test . Videos on youtube showing how to do it .

Jul 14, 2016 | Cars & Trucks

2 Answers

What is the compression on a 2013 500 artic cat 4x4 efi supposed to be ? I have fuel, good spark and only 30psi compression ... The guy had no smoke or anything and drove home just won't start now

The compression pressure is low but that doesn't necessarily mean something is wrong. If lots of spare fuel has been sloshing around the cylinders while trying to start it there will be little oil remaining with the result of a lowering of compression. In addition a very high performance engine will have port or valve timing that will produce little compression at cranking speed.

For engines with normal outputs a rule of thumb compression pressure of above 100psi after lightly oiling the bores will be sufficient to start the engine if all other things are ok.

Jan 24, 2016 | Cars & Trucks

3 Answers


What is the compression on the other cylinders, 110 lbs is low, however it is suffeint to fire so if the plug,coil and injector are working it should fire that cylinder

May 04, 2015 | 2005 Chevrolet TrailBlazer

1 Answer

I have a 99 Ford expedition, Cylinders 3 and 8 are low on compression, what parts do I need to repair the engine?

Usually low compression indicates a leaky head valve or piston rings.
You might have a dirty valve, or a sticky valve, or hydraulic lifter, it fou have those that is.

May 27, 2014 | 1999 Ford Expedition

1 Answer

Compression problem on one valve

If you have low compression in one cylinder (0% or more lower than the rest) first check that the valve follower is not sticking and holding the valve open. The fix is head off and a head job done on the valves IT may be a loose insert seat

Jan 26, 2014 | 1999 Mazda Millenia

1 Answer

No compression in cylinder number 3

Broken or worn compression rings and faulty valves are normally the cause of low compression. I would suggest you take the vehicle to a larger reputable company for a second opinion to start with.

May 05, 2013 | 2004 Mercury Mountaineer

1 Answer

Problems with 2005 Ford Five Hundred

Absolutely!. The dealer shafted you, if he told you nothing was wrong. 80 psi leakage out of exhaust (valve,;;;where else?) is a dead give-away: You need a good old fashioned VALVE JOB. Your exhaust valve, see, is not seating properly, not sealing as it should. It leaks, bigtime in your case, so compression is low, unburned gas escapes out the exhaust (You smelled it!), no power from that cylinder so it idles like ****, and will try to die, and of course, mileage suffers. Sound familiar, Robin?
Now of course the dealer knew what it was. Apparently he didn't want this time-consuming job. All he wanted was his in the door and out money. From the shop mechanics point of view, a cylinder head job is a relatively low paying and time consuming job. But there's no excuse for somebody not telling you that you need a valve job. Take it somewhere else. It's gonna be expensive, no getting around it, cause the head has to come off, but at least it's a whole lot less than an engine overhaul. And just give those figures to your new mechanic-the diagnostics are all done. Good luck.

Jun 12, 2012 | 2005 Ford Five Hundred

1 Answer

When going uphill its weak. already chang sparkplug to new but still the same.when stepping on the gas pedel its not giving more power.

I suspect you have some bad valves, probably exhaust valves. Do a compression test on each cylinder and make the sure the compression of each cylinders is a similar value. You will need to
look up what the compression value should be in a Chiltons or other manual for your car.

This happened to me on my 1992 Tercel. When going up a hill I would punch the gas to the floor
and not speed up until I geared down. I took the cylinder head off and 2 exhaust valves looked really bad. I went to a cylinder head shop and the guy that works there immediately told me I need a valve job and pointed out the beat up looking valves I saw. They machined the valve seats and replaced the bad valves. Rockers need to be adjusted with the engine warm, so youll need to adjust the rocker clearance after you re-install the head and run the engine.

If the compression is much lower in one or more cylinder those are the ones with a problem.

You can get a loaner compression tester from autozone. If you have never checked compression, I will tell you how if you need.

Aug 08, 2011 | 1995 Toyota Camry

2 Answers

My 2000 Lincoln Continental has a cyclinder 8 misfire with 28% low compression. I was told this means I need a new engine. Is that correct?

depends what is causing it..... the low pressure could be head gasket is cracked damaged by that cylinder... crack in head etc.... more then likely something small not the whole engine.... could be piston, head, head gasket etc.... i wouldnt think it would be the whole engine needs to be replaced... hope this helps cheers

Mar 04, 2011 | 2000 Lincoln Continental

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