How to fix this one cylinder without opening the engine?

[derik]

I have Pajero with 3.5 liter engine and some engine missing has been noticed lately and sent to Habtoor and they did not find any missing as its not that big noticeable. I ask them to do the compression test and result was showing low reading in one cylinder. Below are the dry and wet readings. Please suggest how to fix this one cylinder without opening the engine (if possible).

Dry/Wet Engine Compression Test Readings:

1) 140/230  |  2) 150/250
3) 150/230  |  4) 40/90
5) 170/230  |  6) 140/250 

[adil]

Get the everything checked for that cylinder: like spark plug, coil, plug wire before coming to any conclusion.

[reinier01]

Its like adil said, get everything checked out, but judging by the compression figures you supplied, the problem is almost certain not to be related to the ignition system.

There are several possible causes for one cylinder to be low, but the most common reason is a leaking valve, and most often the exhaust valve. However, the reason for the leaking valve may be more difficult to determine.

You don't mention if your engine has hydraulic valve lifters, but you can check this by removing the valve cover on the cylinder bank with the low cylinder. Rotate the engine until the high end of the cam lobe points away from the valve lifter(s). There should be a large clearance between the top of the valve lifter and the cam lobe. If there is only a small clearance, the valve lifter(s) are defective, and you can replace them by only removing the camshaft. You don't need to remove the cylinder head for this, but the timing belt must be removed. If you have a repair manual, you can do this yourself, but I would recommend you have the repair done by a competent mechanic, because Mitsubishi's are famous for running rough after a cambelt procedure.

Bear in mind though that a large clearance between the camshaft and avalbe lifter may be caused by a sticking, or bent valve as well, but the only way t determine this is to remove the cylinder head.

Other possible causes fo low compression on one cylinder include a blown head gasket, a hole in the piston, or more likely, broken rings. The only way to determine this is by removing the cyinder head. If the gasket is blown, it wil not neccessarily manifest by overheating or cooling system issues, since the leak may be into an oil port, but if this is the case, there may be some smoking from the dipstick tube, but not always.

The only other way to repair this issue( if you don't have hydraulic lifters) is to remove the cylinder head, but this is a tricky affair, and I don't recommend you do this on a DIY basis. I hope this helps.   

[bean]

Apart from low compression, do you experience any loss in power, white or blue smoke, hesitation in starting, rough idling, reduction in oil level or any other symptom that you can share.

As reineir said, it may be an exhaust valve lifter, but it could be other issues as well. So explain and we can help you further.

[derik]

Hi Reinier and Bean, thanks a ton guys for awesome explanation, please find my response to answer your doubts:

• Starting is A (No hesitation)
• Acceleration is A+
• Idling is A+
• No white or blue smoke
• Oil level, slightly more than max level (changed last month, less than 2000 km back with mobil1)

However, there is some strange doof doof noise in idle something like (not exactly) a tractor, but when I give gas it goes away. Secondly If car is in closed parking or in repair shop after a while car gases start burning eyes (no visible smoke at all). It smells like fuel burning.

Check the sound recording, forgive the background zipping car around my busy neighborhood.

Pajero doof doof.wav

Edited December 23, 2015 by derik

[ethan]

Have you tried the engine oil additives like Engine Restorer, Gunk Motor Flush or Cerma? If not, may be you can explore that avenue if missing is very mild and no smoke, hesitation or loss of pwer showed up yet.

Your engine sound seems like exhaust valve is sticky or noticeably blocked.

[derik]

Thanks ethan, I don't mind trying any of those stuff what you mentioned. Do you know where to find them in Dubai?

@reinier01 please find the inside picture of the tappet cover removed, and I think it has hydraulic lifter, as mechanic tried to turn engine with quick crank to measure the gap and said, all looks OK (half heatedly), I couldn't get him completely. Appreciate your expert advice. Thanks in advance mate, you are awesome.

[reinier01]

HI derik,

Thanks for the additional information, and the pic as well. Nice clean engine!

I listened to the sound clip, and it is almost certain that you have a defective valve lifter. Let me explain:

Valve lifters work almost like hydraulic "springs", and if they don't release their pressure at a  certain point, the valve does not fully close, hence the low compression. Valves that leak because their sealing surfaces are burned, pitted, or otherwise damaged are not noisy. 

From the sound clip it is clear that there is a serious  misfire present at idle or low RPM. You may not notice it because Mitsubishi engines are balanced very well, and especially their V6 engines. The ticking noise you hear at idle is caused by the valve lifter not maintaining the correct clearance between the rocker arm and the cam lobe. However, at high RPM's, the oil pressure increases, forcing the valve lifter to work, hence, the noise goes away, and returns when the oil pressure drops.

Any type of damage to the pistion that could cause low compression and noises will cause smoking as well. The same goes for the valve seat in the cylinder head. If the valve seat had worked itself loose (rare, but it does happen), the ticking noise won't go away at high engine speeds. In fact, it will get louder, so it seems you don't have to open the engine to fix the problem.

You can remove the valve lifters by removing the camshafts. However, it is not a good idea to replace only the lifters on that one cylinder bank. Repace the lifters as a complete set, but be aware that they may all be noisy when you first start the engine. This is normal, and will go away as the new lifters fill up with oil.

NOTE: Make sure that the new lifters are completely empty of oil when you fit them. You will know a lifter is empty when you can move the little piston freely (with no resistance to movement) for a distance of 5 to 6 mm. If you fit lifters that are not relaxed, the valves will not close, and you will have no compression on any of the cylinders.

TIP: You can relax valve lifters by inserting a straightened out paper clip into the hole in the top of the piston. This releases the internal ball valve which allows the oil to drain, thus relaxing the lifter.

The gas that burns your eyes in a closed space is unburned fuel in the exhaust gas. The air/fuel mixture cannot fully combust in the cylinder with the low compression, but at higher RPM's it might partially burn. Whether it does or not is not important, but what is important is that the exhaust gas is now very  rich in unburned hydrocarbons that can destroy your catalytic converter(s), if you have them fitted.

I hope this helps you out, but please post the result of the lifter replacement when you are done. This will help other members who might also have lifter issues.

[derik]

Thanks a lot @@reinier01 you are really very educated mate and I am blessed to have you here.

From your explanation the change of whole set of valve lifter seems lot of work from Dubai standard, where garage here love to rip off for small midas touch and do nothing. At least now I am certain that two different people having same opinion of half functioning valve lifters at idle speed. Now for me to go for this job or not depend on last question:

"How critical it is"......?

1. Will it get worst or better if I start driving this car daily, as this has been very very sparingly used car like once or twice in a month for short distance since last 2 years?
2. Any engine additives that ethan advised above will help here, I don't mind trying?

[reinier01]

Hi derik,

Glad I could help!

You can certainly try to use the additives ethan mentioned, but be sure to follow the instructions exactly to avoid damaging something else. These additives usually work well if used as directed on the labels.

As for how critical it is- I will certainly not use the vehicle at all in its present condition if it were mine. If the valve lifter seized up completely, you will have no compresion on that cylinder. Moreover, since the injector keeps on sprying fuel into that cylinder, some of it will eventually end up in the oil, which will dilute it, and cause poor lubrication to the rest of the engine.

You could also break the rocker arm, or worse, the camshaft could break if the lifter should disintegrate. I am not saying it will happen, but it is definitely possible. If you are reasonably skilled at car repairs, you could actually do the job yourself. If you want, I can guide you through it. All you need to do is provide me with the pictures I will need. Let me know what you think of this suggestion.