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| EGR flow or not; testing with pressure transducer s and | |
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| Topic Started: Jun 14 2009, 10:44 PM (376 Views) | |
| mwebb | Jun 14 2009, 10:44 PM Post #1 |
 
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 to view the image , right click then- select "view image" you will be able to zoom in if desired top image is long time base capture of a pressure transducer in the tail pipe measuring exhaust pulses from every cylinder yellow synched to cylinder 1 spark red  have pulled the EGR open with my fingers starting at the white line in the center of the image 2nd image is the same , a zoomed section of the same image above . you can clearly see vacuum showing up in the exhaust pulses as i open the EGR , none to steadily as it is hot and my fingers are still burned . this EGR does have flow . on all cylinders , no clogged passages . 3 cylinder 1.0 engine 1996 intake vacuum = 20" at hot idle per scan data at 300 feet above sea level Edited by mwebb, Jun 20 2009, 09:34 PM.
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| mwebb | Jun 20 2009, 09:21 PM Post #2 |
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 same car - with new front 02 sensor and 02 sensor harness has been repaired ,there was a bad connection at the PCM for the heater of the front 02 sensor. the image shows fuel trim totals , short term fuel trim added to long term fuel trim at local speeds on local roads , about 45 mph max speed with one full throttle acceleration to about 45 mph . the TPS value never exceeded 75% , even at WOT , which means there is a problem with the TPS , or more likely the throttle cable is not adjusted correctly and the throttle does not open more than 75% . except for the misfire , this would be considered excellent , not good . as long as sum of fuel trims is under +/- 5% from zero fuel trim adjustment , the system being monitored is in excellent condition. there is misfire at part load cruise as noted - i am leaving the old bosch platinum plugs in it until i can get CKP with CMP with spark waveforms using a high resolution digital storage oscilloscope scope there is a new distributor cap and rotor , same spark plug ignition wires , possible crossfire issue still present . ----------------------------------------- it should be noted here that the EGR was probably open at the time of the misfire and a misfire may be created IF one or more EGR passages are clogged so that all of the EGR flow gets directed to instead of three cylinders , only one or two cylinders causing them to misfire - as that did not show in the images in the previous post , it is probably not the reason for the misfire in this particular system . Edited by mwebb, Jun 20 2009, 09:28 PM.
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| Johnny Mullet | Jun 20 2009, 09:54 PM Post #3 |
"Mullet of Ox"
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It all comes down to the EGR, but not in performance. You can totally remove the EGR from a 1.0L and block it off and it will run fine. Sure, some numbers can be thrown around, but in the long run, it's fine depending on your maintenance procedures for carbon control. When the dreaded "Code 51" comes up, it's because there is so much carbon built up in the port that it clogged. Now imagine the carbon built up on the valves and in the combustion chamber! Yeah! Code 51 means rebuild time. |
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| mwebb | Jun 20 2009, 10:44 PM Post #4 |
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at this point i have no DTCs .... and one of the Mode 6 test for EGR flow has run and passed one other has not run.  but it has only been 50 miles since i cleared the system and it may have run sometime today . spark waveforms will show the answers to the questions , if i should find a questionable cylinder (and even if i do not) i will be capturing at least one running compression waveform because that will show exact valve timing . if i open EGR i have many ways of monitoring EGR flow - i will be documenting what i find , that is part of the fun . |
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| metromad | Jun 21 2009, 09:23 AM Post #5 |
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Moderator
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You go, dude! |
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| 5 O'Clock Charlie | Jun 21 2009, 10:56 AM Post #6 |
New Member
  ![]](http://209.85.62.24/static/1/pip_r.png)
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Dude !! All I can say is  "Where does he get those wonderful toys ?? " 
Edited by 5 O'Clock Charlie, Jun 21 2009, 11:41 AM.
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| mwebb | Jun 21 2009, 10:41 PM Post #7 |
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 the CMP CKP reference is flawed as the engine is accelerating during this image , it was capture just as the throttle was opened to MAX or WOT , WideOpenThrottle to load the secondary spark components - so - there is the CMP CKP reference , the cam shaft position sensor ia an AC signal generator and has one blip per cylinder except for cylinder 2 which has two blips . the crankshaft sensor is an AC generator and has 4 blips between each camshaft sensor signal blip . the reference in that respect is GOOD . the timing belt is aligned CORRECTLY , note the relationship between CKP and CMP that relationship is extremely important . secondary spark shows high resistance in the #2 circuit and a path to ground from each cylinder that does not go through the spark plug ... rats . this is with the bosch platinum plugs that were in it when i got it , this shows misfire on cylinder 2 and it shows cylinder 2 secondary spark is firing into the cylinder one secondary circuit as the sync probe has picked up an extra spike when cylinder 2 fires . most people would have just replaced spark plugs , ignition wires and distributor cap and rotor , saturation bombing , problem would be solved . no test equipment needed ... but wait there is more |
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| mwebb | Jul 1 2009, 09:20 PM Post #8 |
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new distributor cap , new NGK spark plugs , same spark plug ignition wires , holding at steady 2200 rpm with no load , all spark waveforms should be uniform , cylinder three requires a much higher voltage to jump the gap and get the spark event started , but it can not be jumping the plug gap alone as all the plugs are gapped at .039" . bad ignition wire on cylinder 3 , since replaced  right click on the image , select "view image" to zoom |
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| metro95 | Jul 2 2009, 10:10 AM Post #9 |
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New Member
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JM- I recently got a 51 error code. Will Seafoam address this problem or do I really need to pull the exhaust manafold and clean out the port with the braided wire trick? Reading the posts on how many people have trouble removing the manifold, I am not looking forward to snapping studs. mwebb- cool charts. thanks for sharing |
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| pacapo | Jul 2 2009, 04:47 PM Post #10 |
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Nice tools, and it is hoped that the sharpest tools in the shed will always be your brain. Using your data: it might be possible to determine your compression in each of the 3 cylinders. The width (?) of your spark plug tracing during the actual fire is proportional to the compression in that cylinder http://geometroforum.com/topic/1024775/1/#post91746 and is how 'dealer/professional' mechanics of old (past 30 years) checked compression without pulling spark plugs. A higher compression cylinder would have a narrower arc/gap/firing synapse/distance between start and finish of snap. The example above indicates cylinders 1 and 3 to be about the same, compression-wise, and that would be looking at the green tracing. But a little refresh on this subject might be in order. |
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| mwebb | Jul 2 2009, 09:32 PM Post #11 |
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these are just basic tools , nothing exotic here ... ................................... the waveform you speak of can not be used to get compression values as engine rpm is increasing and pressure s in the cylinders are changing because of the sudden rpm change , you would need a waveform from the engine at a constant speed , preferably idle . you can get a relative compression value of one cylinder compared to another by comparing the firing line voltage in KV , the firing line is the first hi peak , those values should be very uniform at idle , idle because ignition timing is very close to TDC at idle and there will be very much more pressure in the combustion chamber nearer to TDC as opposed to 40 degrees before TDC at say 2500 rpm . you are correct in that burn time or burn line will be longer and the burn voltage value lower on cylinders with lower compression , but my eyeballs look to the firing line for quick relative compression values these are relative values , relative to each other only . then you could swag a value to the others if you measured compression in any one cylinder - OR an inductive current probe on the battery cable while cranking with fuel disconnected , synced on spark from ... OR AC coupled Voltage on the battery cranking with fuel disconnected OR analogue MAF OR MAP sensor waveform cranking with fuel disconnected OR FLSi in the vacuum line waveform cranking with fuel disconnected OR FLSe in the exhaust pipe waveform cranking with fuel disconnected or you can use Running compression waveforms - stick a pressure transducer in the spark plug thread and run the engine - there is no better way . Edited by mwebb, Jul 2 2009, 09:38 PM.
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| pacapo | Jul 3 2009, 03:20 AM Post #12 |
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I hope these simple tracings that you have provided do not confuse the casual reader. The voltage necessary to 'spark' the plug lets a person know the compression of each cylinder. Your oscilloscope gives reliable tracings which can be compared to known values. It would be best, as you mention to have the engine in a steady state...idle, for example. When we put an $8 compression tester in the spark plug hole, we "stick a pressure transducer in the spark plug thread and run the engine " and although it is a great way, measuring the kV is the best. It's faster and you don't have to pull spark plugs, get dirty, cut your hands, break wires, or strip threads...you don't need to break out wrenches, sockets, ratchets, and extensions. You do have to do some homework, as you mentioned. You have to get at least one cylinder's compression somewhere back in the history of the scope to give you a scale for your compression. Your experiment gives strong evidence that the Platinum Plus Bosch spark plugs can ruin our 3 cylinder engines. My experience has shown the same thing; the simple NGK spark plugs do much better, even though they're much more inexpensive. Most people still don't get it. They think that a $5 spark plug MUST be better than a $2 'ordinary' plug. There seems to be a pretty decent attempt at a write up of basic ignition theory here: http://automotivetestsolutions.com/images/eignition/IgnitionWaveforms.htm and they have a nice tracing here:  which attempts to explain it. This is a great shot:  with the simple point being - the spark plug is connected to the SECONDARY circuit. Several of the images won't load on that page (they're missing, it's not your computer)...nevertheless, it's a nice read. Here's another easy one to figure out:  And their point is simple. You can have a fast hot burn or slow warm burn...but it's the same 'length of rope'. These three tests analogue MAF OR MAP sensor waveform cranking with fuel disconnected OR FLSi in the vacuum line waveform cranking with fuel disconnected OR FLSe in the exhaust pipe waveform cranking with fuel disconnected sound interesting, but require modification of the engine. Your diagnostic tests so far seem to require adding wires/sensors and not disconnecting engine components. The theory you brought to the Metro Forum regarding kV, however, is most interesting and should apply to most internal combustion engines, not just our Metros. Worth rementioning is the 'GHIJ' part of the trace. This seems to be the business end of the combustion process. If all cylinders show the same trace, then perhaps the engine has even spark and compression.  Your analog, vacuum, and exhaust tests are still more complicated than a simple kV oscillo 'scope' viewing at idle, but the most important part of the tracings is...your interpretation. Glad to see you've applied yourself and are serious about getting these 'econoboxes' running as efficiently as they were designed. I'll bet your engine idles like glass and digs out of the hole like it should. Don't forget to post your mileage results. |
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| Dallas | Jul 3 2009, 04:32 AM Post #13 |
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interesting pictures, ill have to give it another look over tomorrow too. what equipment are you using on this? I skimmed and didnt see it |
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| mwebb | Jul 3 2009, 10:52 PM Post #14 |
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 right click on the image , select "view image" to zoom.the idea is to locate the misfiring cylinder the quickest way , then , prove that misfiring cylinder to be "good" mechanically, fastest way is to capture running compression only on the misfiring cylinder. captured with Pico scope , Pico 6 software ,using Fluke PV350 Vacuum / Pressure transducer. traces removed and stacked up and annotated with AES ANNOwave software . i was holding off putting up running compression waveforms until i had some for the 1.o geo metro anyway , there is no compression gauge that can provide the information that running compression waveforms can . we can see ExhaustValveOpen, IntakeValveClose and with some skill ,Intake vacuum , Peak compression pressure . 30" hg = about -14.7 psi so 1 psi = about 2"hg so -10psi = about 20"hg IF you set zero to ambient local pressure prior to recording the running compression waveform . a 1995 subaru 2.2 2 cylinders are worn out can NOT hold vacuum in the cylinder during the time the cylinder should be filling with Air and fuel prior to the compression and combustion event . note on the two "bad " traces the rise and fall of pressure leading to and dropping from TDC are NOT symmetrical. the LOWEST Red trace is "good" the other two are "bad" secondary spark waveforms are not usually the quickest way to id the misfiring cylinder , but secondary spark waveforms can be a part of the arsenal . sometimes secondary spark waveforms will not even show a misfiring cylinder because ... the spark event is over way before the combustion event is over .  right click on the image , select "view image" to zooma FLSe transducer or pressure transducer in the tailpipe , synced to cylinder one IS the fastest way to ID misfiring cylinders imho. takes minutes to set up and capture - divide 720 degrees by the number of cylinders to see spacing between TDC events ie 720 divided by 4 = 180 degrees or for a four cylinder engine , there is a cylinder firing every 180 degrees , use firing order 1-3-4-2 to see when each cylinder fired , look about 150 degrees after each TDC event for the vacuum pulse and , shazam . when the cylinder misfires , the exhaust valve opens to vacuum not pressure , the vacuum pulse is present in the exhaust and can be ID d and synced to #1 spark to find out what cylinder caused the vacuum pulse . EVO is about 150 degrees after TDC and spark timing adds another 10 to 15 degrees , so just look for the pulse and see when it occurred and you have the misfire on newer cars with COP ignition systems , secondary spark waveforms are not even an option , so we must learn to do without them. , the closest you can get will be spark primary current waveforms or IGT signal ACE Misfire Detective will do this automatically , works with Pico scopes only . ATS Emisfire software will do this automatically , works with ATS scopes only . both work very well , i will post images from each connected to a 1.o geo metro with induced misfire as time allows. Edited by mwebb, Jul 3 2009, 11:01 PM.
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| Woodie | Jul 4 2009, 05:53 AM Post #15 |
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I find this fascinating, but to call it the easiest or quickest way is a bit generous. You're talking about thousands of dollars of test equipment here, and quite a bit of training and experience to learn how to use it and what it means. A Metro with a driveability problem is 95% of the time burned exhaust valves, and a $25 compression gauge will verify it, in less time than it takes to connect all that equipment you're got. |
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7:32 PM Mar 11
