TRYGO:
Each of the combustion chambers of the various cylinders in your car's engine, goes through a series of precise combustion processes of air-fuel via the intake/exhaust valves.
With neither of the combustion chambers undergoing the processes precisely, a deficit is introduced, in terms of either a lean/rich air/fuel ratios in the valves strokes.
A distortion in the firing of the cylinder(s), quickly transcends to what we would normally called, an engine misfire.
There are misfires that can easily be tracked down, and solutions proffered in solving them, while there are others that are a pain, to track down.
Its just frustrating to have replaced all misfiring related parts, and still have the problem not solved.
Today, we'd be treating a peculiar sort of misfire, that has caused a new client thousands in costs of parts replacement and labour.
If you're ready, here we go!
CASE STUDY
CAR TYPE: Toyota Corolla 2010
ENGINE TYPE: 2ZR-FE
TRANSMISSION TYPE: Automatic drive
COMPLAINTS
According to client:
1. Car has being parked for about six months
2. Returned from a journey, and tried starting the car.
3. Engine started finally, but suddenly started experiencing some sort of engine misfires.
4. My mechanic has done all what he could do to fix the problem, but without success.
5. I retrieved a P0301 misfire code with my Bluetooth code reader.
6. I'm scared of driving the car down to your shop Joe!
Could you come pick it up?
VERIFICATION OF CUSTOMER'S COMPLAINTS ONSITE
1. Started vehicle, and confirmed there was a terrible misfire occurring in the engine.
Engine was basically "dancing".
2. Observed excessive black smoke, and foul odour of petrol from the exhaust tailpipe.
3. Personally scanned the car with a professional scan tool, and confirmed same code present.
DIAGNOSIS and FIX
1. Drove the car to the shop, with the hazard light on
2. Because of the violent nature of the misfires, there was a lot of sort of engine knocked kind of noise from the engine.
3. The car was driven, at 30mph, to reduced the load on the engine.
4. Interchanged the ignition coils of #1 and #4, to see if the coils were the culprit.
That didn't solved the problem.
5. Next was to have those spark plugs also replaced, with some sets of test spark plugs I had in the shop, instead of buying new ones.
This also didn't take care of the problem.
This tells me its not an ignition system related problem.
6. I opted to have the fuel injectors serviced, and also interchanged.
I noticed something astonishing during servicing the injectors with carb cleaner.
They were totally clogged with carbon deposits.
The injector on #1 cylinder, had a greater %of carbon buildup on the injector pintle.
That was obstructing the free flow of fuel, and subsequently reducing the fuel pressure on the cylinders.
7. Cleaned up the fuel injectors, and fixed them back; started the engine, there was not improvement.
8. Got a test lamp and a digital multimeter to test the fuel injector's power and ground circuits for either of an open or a short circuits problems.
All the injector power feeds were intact, including the grounds.
With this test, I was able to isolate any ECU related causes.
9. Now, what was in my mind was that this particular problem, is a mechanically induced one, that is narrowed down only to cylinder #1.
Since I have had experiences like these before,
I had already began narrowing down the likely causes to the following:
a) bad top cylinder gasket, due to overheating, can cause the valves to stick in their bores.
b) broken, or worn faulty valves, stems, guides, etc.
broken piston compression rings on cylinder #1.
10. What we saw, opening up the valve cover, with the intention of dismantling the top cylinder head, was surprising.
11. The inlet rocker arms on cylinder #1, were all dislodged from their positions on the pushrods.
This was the actual reason, that cylinder was misfiring, and loosing power.
12. Timed the engine, and had the top cylinder removed and taken to a machinist, for machining.
13. Replaced top cylinder gasket with a composite one, instead of the multilayered one that was originally on the car.
14. Dressed the deck of the engine block, cylinder head, and installed the head, after modifying the gasket.
ANALYSIS OF CAUSES OF THE MISFIRE
1. Closely looking at the valve train components in the cylinder head, and how clean they were, suggested to us that the client must have being properly maintaining his car, and that engine oil degradation was not to blamed for the problem.
2. The absence of an open or short circuit problems on the injector power/ground harnesses, proved that the ECU, and it's wiring, were functional, and there was no need to other a "Brainbox"!
3. Inspecting the inlet port on the cylinder #1 alone as compared to others, showed a huge volume of raw petrol dumped in there.
Obviously, this points to either a valve is not opening at all, or ...
I did conclude that why the rocker arms fell off from their positions in the engine, was basically a buildup of carbon deposits in the bore of the valves on the inlet sides of #1cylinder.
HOW TO PREVENT PROBLEMS LIKE THIS
If you intend to prevent instances such as this, ensured;
1. Engine oils are replaced as at when due.
Not replacing when its due, introduces impurities in the valve train, and cause problems.
2. Use fuel additives, devoid of sulphur contents at least once a month.
This would take care of fuel related carbon deposits on the fuel injector pintle.
3. If this isn't feasible, use carb cleaner to manually clean the injectors.
4. Don't rev your engine when its idling.
This would put more stress on the engine, and cause internal engine problems, such as rocker arm failures, if your engine is equipped with one.
5. Always replace old fuel from a car that has stayed longer than three months.
An j complete combustion process, as a result of bad gasoline, would exert stresses on the rocker arms, and cause lags in the combustion strokes.
PS:
Engines with rocker arm designs, or overhead camshafts (OHC), are known to exhibit problems of rocker arms falling off of their positions on the pushrods, or even falling off and exploding, causing severe engine problems, and suddenly stalling in motions.
This, I have seen on some 2004 Ford Explorers, where the rocker arms are dislodged, and caused an engine to seize entirely.
Well, that ended up having the entire engine replaced.
Regards,
Joseph
DW Nig Ltd
Isolo,
Lagos
www.dxta.com.ng
08066643532 great thought process here bro. and great job once again... however like earlier stated. a compression test wld have told U alot. why? compression on cylinder one would most likely be lower that the rest. dt done U kno U av a compression issue. however where wahala dey be say U will not be able to narrow down if the cylinder is leaking into the combustion chamber (via worn piston rings) or into the intake (if intake valves dont close properly) or into exhaust (exhaust valves not closing completely) this is where a leak down tester comes into play. men this business we need to invest in tools to make the work easier. but car owners no dey like pay at all... would be really glad if we could share such quality knowledge here more often rather than this one dem "ogas" go about slandering eachother... |
Car Talk › Re: Solving A Persistent Cylinder #1 Misfire by AutoMoTech(m): 2:35pm On Jun 02, 2019
