Could a collapsed hydraulic lifter or two give you the same symptom and low compression on that 1 cylinder?

Thanks for the comment! Back in 2004 my friend and I picked up a free 1981 Yamaha XS400 motorcycle that was set out for scrap metal. The engine turned over, so we were curious if we could get it running again. We poured in a gas-oil mix because I thought all small motorcycles were two-strokes haha. Then we got a Chilton's Repair manual and started reading...that was the beginning of my "training". A background in physics and engineering was very helpful, but I have no formal automotive training at all...just a strong passion!

@Jonathan A have you fixed this just happened to me help?

@Jonathan A well mines worse it makes noise while its off

@Jonathan A well mines its hard to explain but long story short i had the car half way on and i try to start it but its was dead i jump it and a ugly noise came on and was jumping i turn it off and back on it was working fine till i get to a friend's house stayed there maybe a hr and my car would not start battery works i try to crank it one more time it didn't start and the noise comes back i turn off the car its still going for 5 minutes at this point something smelled burnt the noise was getting low and lower till it shorten out the battery ..i jumped it now and discounted the negative if i put it back on it makes a low nosie if i can try to send you a video any kind of way to show you i dont want to get ripped off

@Jonathan A the key was out the car noise coming from hood and smelled burnt and a little smoke came out

@Jonathan A its crazy i know ill update you I'm working on it. now

+mrexecutive1 SO what's the correct long-term fix??

Replace or refurbish cylinder head.

mrexecutive1 I guess I was one of the lucky ones. My 05 Cobalt with the 2.2 never had this issue I did trade it in for a Camaro at 80,000 miles, but it still ran fine.

mrexecutive1 I have a 2010 I've been throwing the parts cannon at and I have a persistent cly 4 misfire, I'm fearing i have a leaking valve.

I have the same leak in cylinder 2. Im driving like that an the transmission sounds very bad when stop in traffic. At 11200 miles still worth the money to rectify the head.

hllywd964 first time watching video of him and imma tell you that I’m filling now I never like math but the way he’s doing it to me it’s very impressive and I like that, this young fella knows what he doing!

I have the same exact issue and the same car as you! in 3rd and 4th gear at cruising speed the car will sputter and buck and shake. I don't think our issue is a misfire, my guess is something with ignition or fuel/vacuum. I replaced the mass air flow sensor, coils & spark plugs, cam shaft and crank shaft sensors, 2 oxygen sensors, the evap solenoid valve, catalytic converter, throttle body, fuel filter, and still the problem continues. The exhaust does smell terrible, like a sulfur fire cracker smell. Also my miles per gallon dropped all the way down to 15mpg on the highway at 65-70mph. did you every figure out what was wrong with yours?

Sad to say, I did not. It was costing me more time and money than I could part with. I sold it for scrap and used the money towards a new transmission in my ford. @@tylerdurden9748

eh not really urgent...live with it until it gets annoying :)

+Tom OConnor The cylinder drop test showed that #3 was contributing, just not as much as the others. That alone suggested that combustion was occurring, so the coil and plug were most likely OK. Also the quick "crank and listen" test led me toward a mechanical problem.

Both valves are only fully closed when at TDC at the end of the compression stroke. TDC at the end of the exhaust stroke, the valves are almost closed but not fully

+Typey1 There's never a best-case scenario if it comes to the leak-down test lol

+Randy Gudeahn (ProTech) It's a great tool to pinpoint squeaks, rattles and air leaks for sure!

Your EVAP purge solenoid is stuck open. Replace it. Use ONLY OEM DEALER item!

Thank you for answering. I replaced it like 9 months ago and after that my car kept doing the same after fueling, but now smells like burn after a hesitated and shaking start, I changed the exhaust system, did a tune up and coil changes, the electric mechanic tested and its not a sensor, it says misfire cylinder No.2 P0302

If it wasn't your EVAP and it's still going rough and stalling sounds like your cobalt throttle body is dirty. I found a video on YT how to clean it. Not a hard fix and clean. Make sure you disassemble it from your car because you can 1) Upset the computer while moving the body while it's still attached to the car 2) It holds a powerful charge and is built to actuate ice so it can possibly take your finger off. DISCONNECT IT. Once off spray it will Throttle Body Cleaner and scrub! It will be like a new car! This is the video I watched kzfaq.info/get/bejne/gLZ-oauGm7a9kqM.html also here is a picture of my dirty throttle body instagram.com/p/BYzLyyjHDFf/ before cleaning it. NOTE: This made the car run WAY better but did not get my misfire off. Hope this helps anyone dealing with this issue.

+busjockey1 Of course. Part 2 is just for you!

Cool can't wait to see it. I am a big fan of using pressure transducers, love my wps 500

Just measure fuel pressure 👍

That it would. White board, what would cause an exhaust valve leak here: Broken valve spring, bad valve/seat, valve hanging up

+wtbm123 Part 2 should be up soon :)

Nice. Broken valve spring usually ends up with 0 compression

Can't rule out DIY valve adjustment done wrong. But I don't know this engine or if that's a possibility even. Pet peeve of mine since I've run several old school VW air cooled and on those you adjust the valves with EVERY 3,000 mile oil change or build a lot of spare engines. Sister's 96 Honda has such loud valve noise the techs that have been in there before must be using .012 instead of .004 - insane. On to the solution.

hydraulic lash adjusters here, but I guess you could have one that sticks...

+Billy R IDK what's up with the Autel? Can't let the Verus hog all the attention :)

It depends on the customer. If it's a good friend I don't mind them hanging out. Otherwise I say "This is a really tough problem so I need to focus so I don't have to charge you for an extra hour" lol

motoYam82 good idea. Guess it's how you say it really. i get frustrated when they hang over and keep asking did you figure it out yet or what's this or that? honestly they even annoy me when they stand and don't say anything. most customers aren't like that but the ones that are really ruin my day.

+Niall Seddon Great point, Niall. I have to experiment some more on different vehicles to see if we can develop a more accurate amps-to-psi relation.

+motoYam82 I do a lot of work here in Scotland on LPG (Autogas) vehicles and we do run into valve seat problems now and again. Usually its valve seat wear giving zero or worse valve clearance, when in doubt now and on suitable vehicles I will remove inlet manifold and test with some diesel at the back of the valves and bring the piston to TDC compression, major frothing all round the valve means trouble.

I just got a FelPro top end gasket set...good luck!

+Steve Rob Hey Steve you wouldn't know if this thing would be covered under warranty? It's a 2009 with 92k miles...

No ivan its past the time but i can ask what the fix is at the dealership. My daughter has the same car. Never had a problem.

One theory I've read online is that a faulty injector causing a lean mixture on a cylinder, which burns hotter and deforms the valve seats...I don't know if that's the case here, but might have to do an injector balance test after it's back together!

+motoYam82 Ivan I called my friend and he's saying the opposite ,its not lean he's saying not to take the head off , what he's finding is carbon buildup on the back of the valves building up and to decarbonize the engine. Hope this is your situation . Take care

Thanks for the info Steve! Head's already off; Part 2 will be out tomorrow morning :)

+Andres Ospina Well it's not really voltage, he's measuring amperage on a goofy volt scale so if I'm not mistaken, the 1.88 "volts" is really 188 amps. It's also not really an equation in the sense that I think you are asking - what he's really doing is figuring out the ratio of "volts" to psi on a good cylinder and comparing that to bad one, i.e. V_good/PS_Good = V_bad/PS_Bad. So if you know the good voltage, the bad voltage, and the good psi, then the bad psi is simply v_bad/v_good/ps_good. Which in this case was actually really far off. It's mostly a parlor trick though - if you had a compression gauge I don't think you'd ever rely on the amperage difference between cylinders alone - you'd take a real pressure measurement.

+Andres Ospina There's no magic formula here. Basically the amperage of the starter current is proportional to the power needed to turn over the engine. The humps are occurring during the compression stroke as the load on the starter increases. All we can really say here is that if a hump is lower than the others, then the mechanical resistance of that particular piston is less than the others. Like Ken said below, looking at a simple ratio (Amps to psi) can provide a very rough estimate of how much the compression varies. It may be more accurate to measure the amplitude of the humps not from 0 like I did here, but from the low points on the waveform. So if one hump is 20A low to high, and another is 40A, then the compression is roughly double :)

Thank s Ivan for your time

LOL

haha that was good :)

+12vgs8606 I have one. But it's the base model and can't follow me around on its own too well :)

Well, I guess it will be while before you can hire your own cameraman, huh? Seriously, a wide angle camera and tripod at strategic location should do it. Almost every youtube automotive star tries his best NOT to give vertigo his viewers. To grow your subscribers, this is something you really need to look in to.

dchen345 my 09' cobalt has a cylinder 1 misfire. Compression was bad. It's in the shop as we speak :(

I have an 09 cobalt that has a surging idle, I wonder if its the same thing...

I have a 2010 misfire on cyl 4

8track Abraham I had an 05 and the only issue relatively close was an oxygen sensor that went out. I took it all the way to 80,000 miles and traded it in for a 15 Camaro, it still ran fine.

You would hope that it would run OK for at least 80k miles!

motoYam82 yeah, I feel pretty confident that if I still had it, I wouldn't have had this issue, but I guess it can't be guaranteed either way. I was just ready for a change.

I have an 08. Cobalt ...and an 08 G5 .!Never an issue. PREVENTATIVE maintenance is key ..30K.50K.90K ROUTINE MAITENANCE WOULD HAVE PREVENTED ANY FAILURE...THE CAR ISNT THE ISSUE ITS THE drivers...lmao