Automotive Oscilloscope

[195910]

Hello Everyone,

After reading the only article about M119 Misfire that makes sense :https://www.picoauto.com/library/case-studies/mercedes-w140-s-class-v8-intermittent-misfire

I wondered how much parts were thrown on these cars without actual test results. Techs at M-B Delerships probably don't know how to use one of these and rely on Star which shows nothing about this issue.

A smart method where he determined which distributor cap was the issue by finding which spark plugs had lower voltage (weak compustion and longer duration) then measuring primary voltage and secondary voltage.

Unfortunately these systems are out of the budget range especially that its going to be rarely used (https://www.picoauto.com/products/automotive-oscilloscope-kit/overview)

Any thoughts on this or recommendation for a more economical system for tests and experiments?

regards

 

[LWB250]

I went to trade school in the days when a Sun machine was indispensable for troubleshooting ignition systems, and had a small portable Heathkit automotive O-scope of my own, too. Nowadays you can find inexpensive automotive scopes from Asia for around $200:

https://www.ebay.com/bhp/automotive-oscilloscope

While these are rarely needed, it's one of those tools that as you suggested makes big difference when it comes to troubleshooting our cars' ignition systems.

Dan

 

[195910]

Nowadays you can find inexpensive automotive scopes from Asia for around $200:

https://www.ebay.com/bhp/automotive-oscilloscope

Dan

Yes I saw these but I am not sure about the accuracy ... but then the LH sytem is not the fastest nor most advance engine management system so these would probably do.

 

[samiam44]

My friends always use a little fluke and check to see the 02 sensor response. In older times, for the mechanical injection- the heathkit exhaust mixture portable was very helpful.

 

[gsxr]

... but then the LH sytem is not the fastest nor most advance engine management system so these would probably do.

I see this sentiment frequently. The LH system is not slow or ancient. You want that? Try anything with CIS.

LH EZL systems can pull timing on individual cylinders, and MB's implementation of LH is true SFI, not batch-fire. Fine, it isn't ME17 as used on the twin-turbo AMG's, but snubbing it as old and slow is a bit elitist.

 

[195910]

I see this sentiment frequently. The LH system is not slow or ancient. You want that? Try anything with CIS.

LH EZL systems can pull timing on individual cylinders, and MB's implementation of LH is true SFI, not batch-fire. Fine, it isn't ME17 as used on the twin-turbo AMG's, but snubbing it as old and slow is a bit elitist.

I was just comparing with newer systems!

P.S I don't mix well with those bunch

 

[LWB250]

What an oscilloscope really boils things down to is the ability to see all of the cylinders firing together (not all at once, just to clarify) so you can compare them. As with any troubleshooting, you're looking for patterns and inconsistencies. Frequency of the spark, amplitude of the voltage, dwell, etc., all can tell you something about the health of the ignition and timing. Once you can see each cylinder fire along with it's partners, you'll have a clear pattern that points you in the direction of the problem. Weak spark or bum EZL? You'll probably see an inconsistency across the board with all. A bad coil? Four of the eight cylinders will be affected, as would also be the case with a bad cap or rotor, for example. Bad wire? One of those little spikes will be very different from the other seven.

What's really beautiful about modern technology is the ability to have this stuff hooked up and readable or recording while you drive the car. That wasn't possible in the 70s and 80s, when I was wrenching for a living.

It's not magic by any means. It's just a matter of having the information to make comparisons and draw conclusions. After you do it enough you'll even be able to spot the difference in patterns between different engines and ignition systems.

Dan

 

[northNH]

Sitting in my shop (taking up ~15 cuft and weighing ~100#s) is an early '80s Snap-on complete diagnostic setup: MT498 Digital Performance/Exhaust Gas Analyzer, MT665 Oscilloscope, Tach, Timing Light, dozens of connectors, probes, and hard-to-easily-identity bits. Even the manuals.

Best you could get back then, probably all could be made to work with expertise/experience/obsession.

-FREE-
Actually, I'll pay $25 to whoever takes it away with the promise to make something worthwhile of it.

 

[LWB250]

Sitting in my shop (taking up ~15 cuft and weighing ~100#s) is an early '80s Snap-on complete diagnostic setup: MT498 Digital Performance/Exhaust Gas Analyzer, MT665 Oscilloscope, Tach, Timing Light, dozens of connectors, probes, and hard-to-easily-identity bits. Even the manuals.

Best you could get back then, probably all could be made to work with expertise/experience/obsession.

-FREE-
Actually, I'll pay $25 to whoever takes it away with the promise to make something worthwhile of it.

Dang! If you were closer I would take it off your hands for free!

I see this stuff pop up on the local Craigslist from time to time, and it's difficult not to go after it. One of those "right tool for the right job" sort of things. I would love to have an exhaust gas analyzer, but I've never bothered to look to see if our Asian friends have come up with cheep equivalents for those, too....

Dan

 

[northNH]

Raised on carbs and early FI/turbos, exhaust gas analyzer was THE cat's meow for fiddling with jets, fuel pressures, wastegates, etc.

Oscilloscope's glow always had a "futuristic" feel and usually told me way more than I knew what to do with...

I could get it as far south as NYC in the coming months?
You sound like just the mark.