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No not that common in my (limited) experience. Typically a misfire is triggered by a cylinder under performing. Much less common if one is over performing. The engine controller measures -- via the crankshaft position sensor signal -- the acceleration imparted to the flywheel when each cylinder is on its power stroke. If the acceleration is below a threshold (or above) and for a number of successive power strokes a misfire error is logged.
It is not unknown for a weak or bad cylinder to affect neighboring cylinders. The weak/bad cylinder upsets/interferes with the air flow through the intake and into the neighboring cylinders. But this is rare and I don't like it as an explanation as to why the weak cylinders are not triggering misfires.
That the cylinders with the lowest compression are not generating the misfires does hint, sort of, that the compression tests were not performed correctly. Not saying you are guilty of this. Just want to highlight it is so important that any test performed be done correctly. Bad test results due to bad testing can send one on the wildest of goose chases.
However, a leak down test of at least one or 2 weak cylinders and at least one of the stronger cylinders I think worth the effort. If the leak down test results don't find that much leak down between the weak and strong cylinders that points to bad compression testing. It is either do a leak down test or 3 or redo the leak down tests on several of the weakest cylinders and one strong one and see if the results are the same.
It could very well be that I didn't execute the compression test properly. As with everything else, this is my first car and so this is my first wrenching project.
I read online that you'll need WOT when doing a compression test, which I certainly did not do. I was thinking about unhooking one of the vacuum lines to allow air to get into the cylinders
Hi, Of course, that doesn't mean anything.
I've always wanted to compare the results with someone, and now is the opportunity, but looking at it without any analysis, you have big differences in the readings.
1 - 8,5
2 - 11,5
3 - 10,5
4 - 10,5
5 - 10,5
6 - 10,8
7 - 13,0
8 - 13,2
9 - 13,0
10 - 13,0
11 - 13,0
12 - 12,5
My problem is cylinder 1 and 2. I do not know if the ring may be wrong or it is a head gasket ..
Try with a simple instrument like this one.
It costs around 40 euros with us.
All you need is a compressor to build up pressure.
I don't want to lecture you, but I would probably start with a good compression or tightness check.
Hi, Of course, that doesn't mean anything.
I've always wanted to compare the results with someone, and now is the opportunity, but looking at it without any analysis, you have big differences in the readings.
1 - 8,5
2 - 11,5
3 - 10,5
4 - 10,5
5 - 10,5
6 - 10,8
7 - 13,0
8 - 13,2
9 - 13,0
10 - 13,0
11 - 13,0
12 - 12,5
My problem is cylinder 1 and 2. I do not know if the ring may be wrong or it is a head gasket ..
Did you measure the compression with a hot engine?
I did not if I recall correctly.
Regarding the head gasket, I read online that most of the times if a head gasket is leaking, that is should affect the compression of the two neighboring cylinders.
Originally Posted by M137
I don't want to lecture you, but I would probably start with a good compression or tightness check.
Please do, I've got the feeling that I've still loads of things to learn.
I did the compression test with a cold engine to get the worst possible compression test results, so they must be better when the engine is up to temperature.
However, I don't know if I did it the right way.
During my testing I did the following:
Disconnected the fuel pump
Cold engine
I did not disconnect the coil packs I actually did, dough! , otherwise you wouldn't be able to get the compression tester into the sparkplug thread
Removed one of the two sparkplugs (you'll need the other for compression ), I did only remove the sparkplug of the cylinder that I was testing
I did not remove any vacuum lines or had WOT, to allow air to get into the cylinders
Cranked the engine 5 seconds, or until the needle stopped rising
I did not pour in any oil on bad performing cylinders
Yesterday evening, I did fix one of the two vacuum leaks and the engine ran much better. The cold start was a bit rough though, but I didn't notice any smoke (not that I paid a lot of attention to the exhaust), because: the oil filler cap didn't move at all when the engine started/turned over
I think that the latter is some exciting news, as it might suggest that the piston rings where indeed not seated properly and/or I was using the wrong oil (5W10 full synth --> Castrol GTX UltraClean 10W40 half synth) and/or that the cylinder walls did polish themselves.
A compression test is indeed a very interesting thing to do right now, based on those results I'll judge if I'll need a leak down test.
These are my results when measured on a cold engine.
Pure compression measurement done the same way as you described.
Without the so-called oil test, i.e. pouring a small amount of oil into the cylinder to seal everything more.
As for the oil - so far it's just oil mixed with engine flushing agent.
I bought my CL from a guy who couldn't finish this project and now I'm struggling with it, so so far the engine is not 100% running.
I haven't poured fresh oil on it yet.
These are my results when measured on a cold engine.
Pure compression measurement done the same way as you described.
So did you take out 1 sparkplug of each cylinder, then test each cylinder one by one, or did you only take the sparkplug out of the cylinder you are testing?
The guy showed quite nicely the use of a simple engine leak tester.
Such a test can tell a lot about the condition of rings and valves.
It's by the way.
Very nice, did you manage to do a leak down test yet?
I can only imagine the effort it takes to be able to reach the crankshaft pulley, since everything is very tight down there.
If you've got any details on the size of the nut, that would be appreciated!
Very nice, did you manage to do a leak down test yet?
I can only imagine the effort it takes to be able to reach the crankshaft pulley, since everything is very tight down there.
If you've got any details on the size of the nut, that would be appreciated!
The socket wrench size is 27 mm.
In my CL, I am very easy to do this test because I have disassembled the entire front belt.
I think that normally, without removing the radiator fan, it can be difficult.
I haven't done the test yet. I'm looking for a compressor.
I want to paint the engine compartment and some parts and I am looking for something with better performance, if I find it I will also do a leak test.
The socket wrench size is 27 mm.
In my CL, I am very easy to do this test because I have disassembled the entire front belt.
I think that normally, without removing the radiator fan, it can be difficult.
Just what I thought, I already scaved my arm trying to wiggle in the wrench to release the belt tensioner.
To turn the engine, I need to turn it to the right, facing the front of the engine, right?
Originally Posted by M137
I haven't done the test yet. I'm looking for a compressor.
I want to paint the engine compartment and some parts and I am looking for something with better performance, if I find it I will also do a leak test.
What kind of performance upgrades are you wanting to install? Turbos?
Something else to feed the thought process, everything was fine (a few months ago), until I resetted the ECU to factory settings. Then the rough start and misfire came back
Very nice, did you manage to do a leak down test yet?
I can only imagine the effort it takes to be able to reach the crankshaft pulley, since everything is very tight down there.
If you've got any details on the size of the nut, that would be appreciated!
[QUOTE=tim687;8573823]Just what I thought, I already scaved my arm trying to wiggle in the wrench to release the belt tensioner.
To turn the engine, I need to turn it to the right, facing the front of the engine, right?
Regarding your question ..
17mm wrench.
Wrench move left - belt tensioner goes up.
Just what I thought, I already scaved my arm trying to wiggle in the wrench to release the belt tensioner.
To turn the engine, I need to turn it to the right, facing the front of the engine, right?
Regarding your question ..
17mm wrench.
Wrench move left - belt tensioner goes up.
Ah yes, but the engine itself rotates to the right, right?
Do you know what systems get driven/activated upon cold start, I noticed that my O2 sensors are spiking (meaning running very rich) the moment the engine starts (and then almost stalls)
There is little to no oxygen in the exhaust.
This morning huge blue clouds came out of the exhaust and I needed to restart the car 3 or 4 times in order to get it to run somewhat normal.
I still find it rather strange that if I help the engine to start up, by manually giving loads of gas and keeping the revs up, it doesn't start to misfire and that I did not notice any blue smoke.
I've got the feeling that the cold start program is not running when it's supposed to run. @M137 do you have access to STAR developer mode, so we can compare the variant codings of our ECU's?
Citing: (http://benz.ehost.tj/215_220/215/web...1-p-3011f.html)
Post-start enrichment compensates for the fuel which precipitates on the cylinder walls. The fuel-air mixture is enriched sufficiently until a certain engine speed has stabilized (e.g. 1500 rpm with no gear engaged at +30 °C coolant temperature for about 30 s).
So when the post start enrichment is not active upon cold start, it will wash away the oil from the cylinder walls.
I still find it rather strange that if I help the engine to start up, by manually giving loads of gas and keeping the revs up, it doesn't start to misfire and that I did not notice any blue smoke.
I've got the feeling that the cold start program is not running when it's supposed to run. @M137 do you have access to STAR developer mode, so we can compare the variant codings of our ECU's?
Citing: (http://benz.ehost.tj/215_220/215/web...1-p-3011f.html)
Post-start enrichment compensates for the fuel which precipitates on the cylinder walls. The fuel-air mixture is enriched sufficiently until a certain engine speed has stabilized (e.g. 1500 rpm with no gear engaged at +30 °C coolant temperature for about 30 s).
So when the post start enrichment is not active upon cold start, it will wash away the oil from the cylinder walls.
Unfortunately I don't have STAR. For now I am struggling with sheet metal and painting work. The investment in STAR is still waiting for me..
We did the smoke test yesterday and the results where quite confusing.
With everything attached (PCV system and all the vacuum hoses) the smoke gusted out from underneath the intake manifold and the oil filler cap (when removed).
When detaching the PCV tube, just before the cylinder head cover and plugging the tube that comes from the heat exhanger and thus the throttle body. The massive smoking went away, the oil filler hole did not smoke at all.
The smoke tester ran at around 1 bar, so my thoughts are that we've lifted a gasket of some sort, which should normally be pulled inwards due to the vacuum that is on those hoses.
The thing we know at this stage, the heat exhanger gaskets seem to be fine as the smoke should have gusted out when I plugged up the PCV pipe.
Things that we don't know at this stage; everything else
I did a vacuum test a while ago and it showed around 19hg, which seems to be perfectly fine
I've temporarly enabled ZAS to grand my-self access to mixture formation and it showed that self-adaptation is not active. Now I'm not sure why it isn't active and under what conditions is will become active.
I've disabled it again because it started to rattle.
Any suggestions on tracking down the vacuum leak? I see alot of smoke coming from underneath the intake manifold but I can't really see where it comes from.
Please do keep in mind that it only smokes big time, when the PCV tubing is connected!
I've replaced that gasket 6 maybe 7 times now, so you'd think that I'd be good at this point.
Also, the LTFT's are not ridiculously high or something
I've found out what I think is the problem;
Fuel rail pressure is too low.
It should rise to 3.6 bars upon ignition on, but it only raised to 2.5 bars, after which it dropped down to 0 suddenly.
I've replaced the fuel filter and it did get a little better, but I'm still getting hesitation upon cold start, what is new, is that the car's RPM seems to gradually go up when the engine starts to fire on it's own.
Just like the fuel pressure dropped to low and starts to raise just enough for the engine to start and keeps building until there is enough to keep the engine running.
@M137 It would be awesome if you could do a few fuel pressure tests
How quickly does it rise upon ignition on and to what level?
What is the pressure like at cold starts?
What is the pressure at idle?
What is the pressure when you rev it?
I did notice that the fuel pump was quite loud during the fuel pump DAS test.
I've replaced the fuel filter and pump, seems to run a bit better, but still has cold start issues.
Only cylinder 11 and 12 are misbehaving, showing a 'signal too large'.
Now the lambdas before the TWC have a voltage of 0.999V in the freeze frame data, so I'm guessing that that is the problem.
But then again, how can this influence anything since the car is running in open loop. Could it be that the cat protection is kicking in?
So I've cleaned some of the carbon inside of the engine and I'm now getting a secondary air injection fault code, o2 sensor lambda cylinders 1-3 fault code and cylinder 2 and 3 misfire.
Anybody knows what's going on?
I noticed the following
What is going on?
The 2k rpm section, is from cruising at high way speeds (100km/h)
An friend's expert told me that I had to take a look at the camshaft timing adjusters, as they might be stuck. This theory is further build on, when I told him that ZAS rattles when it's trying to turn off bank 2.
05-30-2022, 03:25 PM
, otherwise you wouldn't be able to get the compression tester into the sparkplug thread
), I did only remove the sparkplug of the cylinder that I was testing
