PicoScope 7 Automotive
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Opel Astra G 1.6 Z16SE petrol engine with a misfire
Opel Astra G 1.6 Z16SE petrol engine with a misfire
Welcome to another Case Study.
"Pacient" is an old Opel, engine 1.6 with 8 valves, 2001. Customer complain, one cylinder misfire, with two faultcodes as follows:
P0302 Cylinder 2 misfire detected
P0130 O2 sensor bank 1 sensor 1 circuit malfunction
Vehicle history, it came into the garage for a blown cylinder head gasket. It appears that there was no misfire problem when vehicle came in. Cylinder head has been verified and cleaned, same for the cylinder block surfaces, gasket replaced and new cylinder head bolts. And somehow this problem occured.
Vehicle repair was needed asap, as the garage Owner had to go in holidays the next day. I was called, so I took my tools with me and head straight to the location.
Engine started, problem confirmed. I have removed the injector plugs and coil pack plug, cranked the engine. It was pretty obvious that at least one cylinder was low on compression. But which one. No time to waste, Picoscope out, WPS500X out, and for the certaintly, I went to measure all cylinders.
To my little surprise, it was not the cylinder 2 as per fault code generated, but rather cylinder 1. 54 mbar peak pressure and -38 mbar underpressure. Basically no pressure, mechanical problem confirmed, but where is it?
Next step, connected the pressure sensor to the intake manifold, at the hose towards the carbon canister. Started the engine and I am looking at this.
Cannot get my head around, I see two companion cylinders pulling more underpressure and the other two less. I haven't really understood it to this day, but well, I now need I have a problem with the intake valve on cylinder 1.
For the fun of it, I put the pressure transducer in the exhast manifold, yeah, same uneven waveform.
So, I think, if there isn't compression, also the exhaust is affected, but if the problem was on the exhaust side of the engine, then the intake should of been look better? Well, I guess depends on the case.
Now I am basically done with the diag, I am the electrician, not the mechanic. But I look to this lad, as he told me, he did not know anymore, was late, he was obviously tired and holiday did not look to his grasp. Well, I'll do my best.
Pressure transducer back in the cylinder, start the engine, rev it up, I see 3.1 bar peak pressure, 90 mbar exhaust stage pressure, -480 mbar underpressure in the intake stroke. But if the valve is stuck open, should of not that be close to zero? Again, I am totally confused. But what is important, waveform does not look right, this cylinder does not breath correctly.
Let's continue. Valve cover off he takes, the good old youtube advice, do a PROPER visual inspection.
And what I notice, comparing cylinder 1 with 4 rocket arms on intake valve, that number 1 is about 4 to 5 mm higher sitting. This means only one thing, the hydraulic lifter is stuck, it does not properly operate due to carbon deposits.
How to get it out, as this engine requires cylinder head removal, new cylinder head bolts which we did not have, etc. Since I am no mechanic, I apply to the service information, and good news, it appears we can remove the camshaft, by removing battery, ignition coil and compressing all 8 valve springs, using 8 of these tools.
But wait, we don't have the tools either. Commoon ....
Then I get another idea, I've seen it on youtube with Mario, we'll compress only cylinder 1 intake valve spring. Then the rocker arm should release. Let's use what we have, a long 13 mm socket and half of an exhaust pipe clamp, which fitted perfectly on the valve cover bolt holes.
I turned the camshaft, compressed the spring, fitted socket and clamp in the hole, and slowly rotated the camshaft. Success! Rocker arm out, hydraulic lifer out, guess what. Yes, it is stuck. Long story short, took forever to fully dismantle it, clean it, fill it with oil and compress it.
All back, I still had the pressure transducer in the cylinder. Crank the engine, I am looking at 15 bar pressure and perfect waveform. In the joy of the moment, I get a hug and I am almost in the air. Tried to kind of save the waveform but someone I mess up and end up with an empty file. Sorry.
He can go in holidays, that's all it matters now! Could I have done it wihout Pico? Maybe. But it would of took a lot more time. Using Pico tools gives me confidence and that's all it matters. If someone can actually explain me what I'm seeing in the waveforms, I would be grateful.
Till next one.
"Pacient" is an old Opel, engine 1.6 with 8 valves, 2001. Customer complain, one cylinder misfire, with two faultcodes as follows:
P0302 Cylinder 2 misfire detected
P0130 O2 sensor bank 1 sensor 1 circuit malfunction
Vehicle repair was needed asap, as the garage Owner had to go in holidays the next day. I was called, so I took my tools with me and head straight to the location.
Engine started, problem confirmed. I have removed the injector plugs and coil pack plug, cranked the engine. It was pretty obvious that at least one cylinder was low on compression. But which one. No time to waste, Picoscope out, WPS500X out, and for the certaintly, I went to measure all cylinders.
Next step, connected the pressure sensor to the intake manifold, at the hose towards the carbon canister. Started the engine and I am looking at this.
For the fun of it, I put the pressure transducer in the exhast manifold, yeah, same uneven waveform.
Now I am basically done with the diag, I am the electrician, not the mechanic. But I look to this lad, as he told me, he did not know anymore, was late, he was obviously tired and holiday did not look to his grasp. Well, I'll do my best.
Pressure transducer back in the cylinder, start the engine, rev it up, I see 3.1 bar peak pressure, 90 mbar exhaust stage pressure, -480 mbar underpressure in the intake stroke. But if the valve is stuck open, should of not that be close to zero? Again, I am totally confused. But what is important, waveform does not look right, this cylinder does not breath correctly.
How to get it out, as this engine requires cylinder head removal, new cylinder head bolts which we did not have, etc. Since I am no mechanic, I apply to the service information, and good news, it appears we can remove the camshaft, by removing battery, ignition coil and compressing all 8 valve springs, using 8 of these tools.
Then I get another idea, I've seen it on youtube with Mario, we'll compress only cylinder 1 intake valve spring. Then the rocker arm should release. Let's use what we have, a long 13 mm socket and half of an exhaust pipe clamp, which fitted perfectly on the valve cover bolt holes.
I turned the camshaft, compressed the spring, fitted socket and clamp in the hole, and slowly rotated the camshaft. Success! Rocker arm out, hydraulic lifer out, guess what. Yes, it is stuck. Long story short, took forever to fully dismantle it, clean it, fill it with oil and compress it.
All back, I still had the pressure transducer in the cylinder. Crank the engine, I am looking at 15 bar pressure and perfect waveform. In the joy of the moment, I get a hug and I am almost in the air. Tried to kind of save the waveform but someone I mess up and end up with an empty file. Sorry.
He can go in holidays, that's all it matters now! Could I have done it wihout Pico? Maybe. But it would of took a lot more time. Using Pico tools gives me confidence and that's all it matters. If someone can actually explain me what I'm seeing in the waveforms, I would be grateful.
Till next one.
Re: Opel Astra G 1.6 Z16SE petrol engine with a misfire
Crikey Liviu!
That brings back memories I used to do loads of those camshaft back in the day. The camshafts were made of chocolate on the early production models and "Sykes Pickavant SP 022500 Camshaft Follower Press" was the tool of choice in the UK.
In Fact there is an ebay listing Here and even more spooky I have not one but two of these sets in my tool store. I know this because I was recently re-organising the "Stuff" I have accumulated over the years and considered whether I really need to keep either or neither of these kit and guess what? Being the sad old git that I am I could not quite bring myself to put either of them in the scrap bin!
Good spot on call with the pressure analysis, and a fantastic example of working smarter not harder.
Sadly from your colleagues point of view he would appear to have neglected to at the very least test the hydraulic tappets and on those motors preferably always strip, clean and re-fill before assembly.
But hey! I bet he will learn from the experience and not make that mistake again.
Kev.
That brings back memories I used to do loads of those camshaft back in the day. The camshafts were made of chocolate on the early production models and "Sykes Pickavant SP 022500 Camshaft Follower Press" was the tool of choice in the UK.
In Fact there is an ebay listing Here and even more spooky I have not one but two of these sets in my tool store. I know this because I was recently re-organising the "Stuff" I have accumulated over the years and considered whether I really need to keep either or neither of these kit and guess what? Being the sad old git that I am I could not quite bring myself to put either of them in the scrap bin!
Good spot on call with the pressure analysis, and a fantastic example of working smarter not harder.
Sadly from your colleagues point of view he would appear to have neglected to at the very least test the hydraulic tappets and on those motors preferably always strip, clean and re-fill before assembly.
But hey! I bet he will learn from the experience and not make that mistake again.
Kev.