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Cylinder 3 Problem And Compression Test Results


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Heya,

I put a similar post as this onto the old taurus site because I wanted to post the follow up I'd promised to the thread I already started before the changes came about, but I prefer this forum so I'm posting it here too.

The background is I did my first code reader tests on my 1994 Taurus GL 3.0V6 with my new code reader and I got code 30 while the engine was running, which was supposed to indicate an issue with cylinder 3, issue unknown. So today I finally had a chance to do the compression test (changed the spark plugs and air filter while I was at it) and the results are that yes, cylinder 3 is not up to par. On the dry tests, all cylinders were 145-155 except cylinder 3 which was 120. Also, all six cylinders built up pressure the same, about 4 strokes to the max number.

I still have no really obvious symptoms, just trying to learn more about the code to plan for future repairs. I tried really hard the last few weeks to look for any symptoms, the only thing I noticed was sometimes when I'm stopped at a light the idle will suddenly get a little bumpy for maybe 20 seconds, then return to smooth and normal. So I don't have much to go on. Any ideas or experience with low pressure on one cylinder? Also, I saved the old spark plugs so I can inspect them for any clues.

And thanks a bunch for all the good info over the past few months.

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OK, not to treat you like you are stupid, but I got to ask.

DID you keep the accelerator floored during cranking? Lots of people DO NOT, and that is wrong. What happens is the valves may leak, and the closed throttle blade influences test results.

If you did, cool.

Next thing. You may want to put a tablespoon or two of oil in the offending cylinder, and see if the compression comes up. If it does, you may have a weak ring on that cylinder. If it doesn't it could be valve, or head related.

Now, I have no hard and fast rule, but I like to see cylinder pressures within 10% of each other, And 120 falls short of that threshold, so we should figure out why that is.

Tim

EDIT: Would it be possible to get a pic of the plug that came out of three, and one of the other plugs?

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You may want to put a tablespoon or two of oil in the offending cylinder, and see if the compression comes up. If it does, you may have a weak ring on that cylinder. If it doesn't it could be valve, or head related.

... thinking the same thing. Some "snake oil" products may help. AutoRx can help with dirty rings. SeaFoam or Marvel Mystery Oil can help with dirty valves. Try Zorin's suggestion and post of pic of the bad cylinder's spark plug compared to a different cylinder if you can.

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Well the good news is, yes I did keep the accelerator floored during the tests. My other option (according to the directions on the test) was to prop open the throttle plates manually but Hayne's said I could just floor the accelerator so I went with that option. When I did the dry test I just did a regular test. Then on the "wet" test, I put 2 squirts of engine oil into each cylinder and did the test again. All of the cylinders went up somewhat (5-15 up), but cylinder 3 went up the most, from 120 to 140.

The bad news is I forgot to label the spark plugs. I had masking tape and a pen all ready to label each one as it came out, but I got so preoccupied with what I was doing that I forgot. They all look about the same, I took a picture of all of them together. I checked the gaps, each one is about .44-.45 except one that is.48, not sure if that one is cylinder 3 or not though.

post-39-015358200 1279702777_thumb.jpg

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Code 30 is Cylinder 3 Failed Balance Test. Sounds like maybe rings. Do you have access to a differential compression gauge? That would pinpoint the worn component.

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Code 30 is Cylinder 3 Failed Balance Test. Sounds like maybe rings. Do you have access to a differential compression gauge? That would pinpoint the worn component.

I'm glad he said that. It saved me the trouble of saying that. And I really didn't want to say that.

Tim

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I'm still learning about all of this as I go along. A problem with the rings, is that something that would require an engine rebore? Sounds like a financial disaster. Or at least something that would take a long time to save up for. Probably longer to convince my husband to let me do it. He's not quite as in love with my car as I am.

I don't have a differential compression gauge, to be honest I'm not totally sure what it is but I will google it. Maybe something I could ask for for Christmas? I got the compression tester for my birthday so my best bet is Christmas to get anything else car related. That would enhance my neighborhood crazy car lady status if I was messing with the engine in the cold of winter. Love that Taurus though. Whatever needs to be done needs to be done, it's just a matter of having the time to save up some money.

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it would honestly be cheaper and easier to find a low mileage engine to drop in and just keep driving it until then. the only problem that you would really have if you continue to drive it is that it will get worse most likely or if it is bad enough it could take a cat out.

there is a possibility that the rings are just sticking and need a good cleaning to loosen up. i am not sure of how to do this though but others will chime in i am sure. i think i heard seafoam is good for doing this but not sure...

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Ok, here is what the differential compression gauge (cylinder leakage tester) looks like:

post-24-039512100 1279821888_thumb.jpg

The purpose of the differential pressure test is to identify leaks and find the source of the leaks in a cylinder, under static

The cylinder to be tested is brought to top dead center (TDC) of the compression stroke. This ensures the valves are closed.

The gauge is conected to a compressor and 80 PSI is aplied as indicated on the master gauge. When the valve is opened air is allowed to flow into the cylinder and pressure in the cylinder is indicated on the second gauge. The second gauge will read lower due to inherent leakage past the rings with the engine static. What you are looking for is a really low reading and indication of air leaking past the rings (can be heard throught the oil filler cap or dipstick) or valve leakage (heard through intake manifold or exhaust pipe). You can also diagnose a bad head gasket if the leakage is heard through the radiator or in an adjacent cylinder.

This is the way compression tests are performed on reciprocating aircraft engines. With 80 PSI applied, generally 65 PSI was the low limit. Any lower than this indicated excess leakage. For an automotive engine, you are probably looking for no more than 20-25% leakage.

Harbor Freight has a tester for $39.99 http://www.harborfre...ster-94190.html

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Ok that test sounds good maybe in september. The gauge I can manage, air compressors that I've seen are a bit expensive. But my husband's been wanting a compressor the last year, so when there's a little extra income in september he might be for the idea of getting one.

I know I definitely wouldn't know how to install a new engine, at least not anytime soon. There's a military spouse certification funding program I'm going to try to get into and I had wanted to take mechanics classes. The problem is jobwise some IT courses would probably be better so I'm wavering on whether or not I can do that. If I could, I could probably install a new engine myself, otherwise I'd have to pay for labor to do it.

My current engine has 80,500 miles on it. I'm not sure if I could find another engine with lower mileage then that. The reason I have less then 100,000 on a 1994 is that the car sat pretty much from 1995-2000 so it didn't accrue as many miles. So I'm not sure if a new engine would be a better idea then reboring with that mileage? Still hoping the problem is something simpler like the head gasket or something if that's possible. I know eventually it will need a new engine, new transmission, etc, but I'll find a way, it will survive.

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I would try the additive products while waiting. First I would add some Marvel Mystery Oil or SeaFoam to a fresh tank of gas. Next, I'd pour some through a vacuum tube on the intake while the engine is running. Finally, I'd add some to the oil before an oil change. After a fresh oil change, I'd run a cycle of AutoRx. AutoRx works great, but requires a couple extra oil changes. It's about $25 for a bottle. MMO and SeaFoam are very similar products that can be used the same way, but MMO is much less expensive. If you add the suggested amount on the label to the engine oil, do not drive the vehicle. The oil will be very thin from all the distillates. This step is really only recommended if you change the oil yourself and can allow the engine to sit in the driveway and idle for 15 minutes before changing the oil.

Does Ft. Bragg have a Craft Shop? The posts I was stationed at all had a Craft Shop, which was an auto mechanic shop for DIY'ers. It charged a minimal fee to use all the tools and equipment with certified mechanics on hand to offer advice and assistance. Great place. I often maintained and repaired fellow soldiers' vehicles at the Craft Shop while off duty for some extra cash.

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Just to let you know I did check and found that there is a Craft Shop at Ft. Bragg so that could come in really useful. Still haven't tried the additive procedure but I plan to in the future. Thanks!

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  • 11 years later...

Finding out that on these engines with the low compressions on only one cylinder it most likely is a valve & mostly an intake valve. My 2000 Ford Tarus is proof of this as 5 are hitting even compressions but the hardest one to get to is No.6 & that is the one on my car that is low & when I romp the pedal it makes that intake suction popping sound which is an intake valve. Runs & drives still but have to deal with it & car has 111,000 original miles on it & whole car looks newer still other than the clear coat is peeling off but all power options work well, air blows cold & trans is perfect. No water in oil, no signs of head gasket issues just an angry ole intake valve on the worst to get at cylinder, yeah-oh boy crap. So what am I to do at this point & get it rightly done instead of a single fix to one cylinder? Whole top end completely revalved & send the heads in for that plus magifluxing with intake manifold ect...So is this worth the cost on a older Ford Tarus that reads "TOTALED" on the Title? NOPE not to any of you maybe but to me the car has good qualities still there & zero dents ect...So why is it declaired "TOTALED"? Have no ideal & cannot find out why so could it be because of book value if engine is bad ect... Needs front brakes but is all I can find wrong with it. Anyways threw in my two cents on this issue. OK you all have a Great week & be safe & wise.

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  • 1 month later...

Is your 2000 a OHV Vulcan or DOHC 24V Duratec?

God help you if you have the single year produced 2000 Duratec. 

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