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2005 Ford Focus ZX4 SE 2.0L Duratec (I think) 220,000 miles
Had a few hard starts over the past couple weeks. Then suddenly wouldn’t start. Cranks fine, and almost fires barely.
Compression ranges from 40-80 psi (up to 100 with wet compression test). Compression was 210-215 four years ago with same gauge and same testing method (engine cold, all plugs removed, wide open throttle, fully charged battery)
For what it’s worth, spark and fuel are good. Each coil-on-plug/spark plug combo produced strong blue spark when removed and laid on engine ground. Fuel pump and assembly were replaced a month ago (check valve had failed). There is fuel at the rail (no shrader valve available to test pressure, but I disconnected the line to verify fuel). Noid light confirms that each injector are receiving signal. And plugs smelled like gas when first removed. There do not appear to be any air intake or exhaust restrictions.
Only other detail that is probably not related: for the past month there was an exhaust smell in the cabin when running the heater. When pulling the plugs I discovered that one plug was loose and it was clear that combustion gas and crud had been escaping around it.
So it would seem that my mechanical timing is off. Chain jumped a tooth? But why? Stretched chain? Failed tensioner? Maybe the crank sprocket rotated on the shaft or something (I guess they’re not keyed to the shaft so this is possible?). I do not hear any chain slap.
What else could it be? Does this vehicle have some sort of variable cam timing system that could be screwed up?
And what should I do? Pull it all apart (not the worst job ever) and look for misaligned timing marks? What if I skipped timing and bent a valve?
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[quote=”ToyotaKarl” post=187698]I am not sure why you keep looking for a supernatural explanation on why your valves are not seating.
Several posts ago you mentioned you saw a half moon shaped shiny spot on a piston. That is a good indicator a valve came in contact.
Since you dont like my (or anyone elses possible explanation) try taking your head with valves to a machine shop and ask their opinion…
I’m out…[/quote]
” Well, on at least piston #1 I can see a single crescent shaped shiny mark off to the side of the piston below one of the intake valves. ”
“ Cylinders 1 through 3 are all leaking out the intake valves. (Nothing is leaking out the exhaust as stated earlier.) ”
Unless you have a engine / head design that is completely different what ford uses.
The only air passage from the combustion camber back to the intake that I am aware of is via the intake valve and seat.
Dismiss the idea of weak valve spring(s) being the cause due to the fact you are pressurizing the cylinder(s) and forcing the valves closed during a leak down test.+1 with what Karl states.
Either burnt, bent valves or seats.
Suggest you take the head to a qualified machine shop and have them evaluate the issue.+1 to what Karl and nightflyr said. As I mentioned before, the amount of valve distortion can be too small to be seen, but put it on a valve grinder and it can be immediately heard by the sound of the machine. Stop denying that the valves aren’t the problem, as they are. If there is an impression on the piston head, then there was sufficient contact to bend the valve however slight it may be. Any competent machinist will be able, and is the only reliable source, to confirm whether the valves are indeed bent or not. The issue you are having is with valve sealing. Whether they are bent or not is not the takeaway. The fact that your valvetrain has problems is the takeaway. Since you have already disassembled the engine, just take the head to a machinist for confirmation and repair. This really is the only answer to your situation. Even if your valves aren’t damaged, the head needs to be checked and prepped by a machinist before engine reassembly or else you’ll be pulling it off again soon.
You guys are automotive forum rockstars.
I took the head to the machine shop. The valves are NOT bent. They did not contact the pistons. No valve float, no mechanical timing issue. The shiny mark I saw with my shitty inspection camera must have just been glare/reflection/a mark in the carbon from the inspection camera itself.
There isn’t any carbon build-up on the valves or seats. The valves are not burnt, cracked, nothin’.
The sole proprietor of the machine shop for the past 30+ years said, “sometimes valves just lose their seat.” He reground them and now they seat perfectly. I was able to pull near perfect vacuum on all the intake ports. I’ll have the car back together this weekend and I fully expect it to start and run perfect.
I’m not looking for a supernatural explanation. Just an actual explanation. And all of those offered so far have been proven wrong. Nothing to be butt hurt about.
I want to understand what happened because I want to know if it will happen again or if it can be prevented. At least one intake valve on three out of four cylinders weren’t seating well enough to maintain enough collective compression to start the car. Cylinder 4 was fine.
In place of trying to disspell every ones suggestions..
Perhaps you need to read the posts a bit more carefully.
You were told the seats were a possible failure point.Sorry to disillusion your expectations.
BTW… trying to redeem yourself from your original post ” Nothing to be butt hurt about. But quit +1’ing Karl.”
Very classy response to someone trying to assist you.
From your own statement:
“The shiny mark I saw with my shitty inspection camera must have just been glare/reflection/a mark in the carbon from the inspection camera itself.”Before passing judgement and credibility on advise given, did you even bother to inform the forum of YOUR inaccurate diagnosis.
So anyway, the valves aren’t bent. Got any idea why my valves lost their seat?
This article has good info that helped me understand how my valve seats may have warped or receded. My guides were ever so slightly worn (although not enough to smoke) and several years ago one valve clearance on a single valve was about .001 out of spec. Could have got worse and maybe excessive valve train wear caused the seats to wear.
A lot of stuff in that article relates to burnt valves which I didn’t have, but perhaps “excessive valvetrain clearance can make the valve seat with heavy impact, causing valve face wear.”
No clue what caused it , I think I expressed my guesses earlier .
Just hope it runs for you .
God bless
WyrFinal update and summary:
Contrary to the title of the post, I had low compression on cylinders 1-3, not all four. (Faulty compression tester to blame, or maybe, just maybe, dying battery from all the cranking, but I don’t think so.)
Leak-down test was essential to determine that intake valves were the primary source of the leak. Note, however, that the exhaust valves were leaking a bit also which can confound the leak-down test a bit. Be sure to open throttle valve for test, lest air flow past a leaking intake valve, into the intake manifold and back into another cylinder (which happens to have it’s intake valves open) then out a spark plug hole (if plugs are removed). This would make it look like a blown head gasket.
Pulled the head and determined that at least some vales just plain weren’t seating tight. Shining a flashlight fro behind (in a dark room) showed the leak on some. Rigging up a vacuum tool showed the leak on all. This was confirmed by a vacuum test at the machine shop.
Machine shop confirmed that valves were not bent, agreeing with my own test using a drill press and a dial gauge.
No build up was found on any of the valves or seats.
I had the vales and seats machined, as well as the head decked to save me the time of cleaning the head mating surface myself. Machinist also said that valve guides were a bit sloppy (although I don’t think I was consuming any oil). Had new guides pressed in, and new seals installed since they came in the head gasket set anyway.
Car went back together and runs again. Just a very tiny bit rough, but strong as ever. At 220k, it’s entirely likely that any tiny roughness is the result of injectors, fuel filter, plugs that haven’t been changed yet, who knows what else.
Lesson’s learned: If you use any abrasive sanding method to clean the aluminum block mating surface, and it’s too difficult/impractical to plug the coolant passages, flush the cooling system after or expect your water pump to fail after a couple days. Mine is not leaking yet but it’s squealing.
Leak-down test was essential to determine that intake valves were the primary source of the leak. Note, however, that the exhaust valves were leaking a bit also which can confound the leak-down test a bit. Be sure to open throttle valve for test, lest air flow past a leaking intake valve, into the intake manifold and back into another cylinder (which happens to have it’s intake valves open) then out a spark plug hole (if plugs are removed). This would make it look like a blown head gasket.
Not exactly sure how you did a leak down test..
But the common method is to set one cylinder to TDC compression stroke, remove the spark plug of the set cylinder and install the leak down gauge.
Lock the crank from turning ( depending on the amount of pressure used.
Pressurize the cylinder under test.
Check the, TB intake, exhaust tail pipe, remove the radiator cap ( look for bubbles ), remove the oil fill cap and listen for air leakage.Having a hard time understanding how and where you introduced pressurized air into the engine.
So at first I had all the spark plugs out and I didn’t prop the throttle valve open. I set #1 to TDC of compression stroke. When I introduced pressurized air, it escaped out the leaking intake valve into the intake manifold. But since I didn’t prop the throttle valve open, the pressurized air flowed into the intake manifold and then into whichever cylinders had intake valves open since they were on their intake strokes (as well as a little bit into whichever cylinders also just had leaky intake valves. And since I had all the spark plugs out, that compressed air flowed straight out the spark plug holes. You can see how without verifying propoer test conditions, someone could easily say. “Oh, well you obviously have a head gasket leak since air is leaking from one cylinder to another.” But in my case air was “leaking” from one cylinder to non-adjacent cylinders.
I then reinstalled the spark plugs, but I still neglected to prop open the throttle plate. Now the compressed air from cylinder 1 flowed past the leaky intake valve, into the intake manifold, back into other cylinders and out any of the open exhaust valves. (Remember that 3 cylinders had substantially leaky intake valves, and all cylinders has slightly leaky exhaust valves.) Again, you can see how without verifying proper test conditions, one could easily say, “Oh you’ve got leaky exhaust valves since the air of coming out the tail pipe.”
When I next propped my throttle place open, air flowed freely out my throttle body and I finally figured out what had been going on. (Note that while most of the air follows the path of least resistance, it still goes everywhere. With throttle plate propped open, and spark plugs removed, some air still came out the spark plug holes to varying degrees of pressure depending on how far open their intake valves were.)
The moral of the story is that it is important to leave spark plugs in and prop your throttle valve open when doing a leak-down test. I often see instructions (including yours) that leave out one or both of these important steps. The other lesson is that leaks on all or most of you intake and exhaust valves make diagnosis a little trickier. I suspect that a single burnt (aka cracked or broken) valve is much easier to diagnose. Although I guess my symptoms wouldn’t be so different from bent valves.
A quick update while I’m at it: after having the valves reground several weeks ago, everything continues to run great.
Although I didn’t block off the coolant passages while sanding the the block, everything is fine. (Note that the shape of and design of my coolant passages made it very difficult to properly block off, and that my water pump is easily accessible if I need to change it.) Also, the oil passages were only blocked for 75% of the sanding, and I changed the oil before running the car once the repair was done. So hopefully any grit is handled by the oil filter. Surely enough time has not passed for any wear to show up.
Can’t remember if I mentioned it earlier, but what I thought was maybe a squealing water pump pulley shaft that developed a day after the repair, turned out to be only a screeching belt as verified with some belt conditioner. A liberal application of belt conditioner took care of 95% of the noise. Flipping the belt around took care of the rest. I will now always mark the direction of belt rotation before taking off and putting back on old belts.
With all the information available and with some basic common sense.
Sorry to have to burst your bubble once again.
No need to leave all the plugs installed ( no idea how you came to that conclusion )
All that is required is to have the cylinder under test @ TDC compression.
Introduce compressed air into the cylinder via the spark plug port.
Then check the following.
A – Place your ear by the throttle body.
Now try to follow some basic logic.
If you introduce compressed air into a “sealed” cylinder and there is any air passing through to the intake manifold AS YOU stated, the pressurized air flowed into the intake manifold SURPRISE, the point of origin (not withstanding a cracked head) will be the intake valve or seat of the cylinder under test
B – Remove the radiator cap and look for bubbles
C – Remove the oil fill cap or remove the dip stick and listen for air.
D – Put your ear to the tail pipe and listen for air.Seriously, this has been done for years uncountable by many.
Simple fact you had no idea going into the testing what was needed / required nor what was to be expected and how to go about it.Much akin to the fact that it was originally suggested you to check valves and seats.
[color=orange]”+1 with what Karl states.
Either burnt, bent valves or seats.
Suggest you take the head to a qualified machine shop and have them evaluate the issue.”[/color]
Guess the forums suggestions do not carry the “expert opinion” class
But you needed a “expert opinion” …
“The sole proprietor of the machine shop for the past 30+ years said, “sometimes valves just lose their seat.”Wow, ain’t that just too amazing.. You were told valve seat here and it turned out to be a valve seat.
INCREDIBLE, SIMPLY INCREDIBLE.
Wonder how that happened?????????
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