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Ignition with Distrubutor

posted Jun 12, 2016 11:23:13 by Johan
4cyl engine Audi 1988 running bad smell fuel high CO 7%, tested hall effect signal and primary circuit at coil with 2 channel Pico signal line up with each other guess it is ok,
King lead from ignition coil to distributor probed with a secondary ignition probe nice pattern every time.
Cyl 1 and 2 secondary no spark line just a firing line straight up... good firing line at times can I call the ignition wire just from that and also change cap and rotor?
Checked the 02 signal (new sensor) pegged lean can happen with raw fuel in exhaust I guess making hole matter worse.
Primary current waveform is a classic perfect waveform secondary oscillation in begin nice ramp.
Can send picture latter if needed.
[Last edited Jun 12, 2016 11:30:10]
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24 replies
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AndyMacFadyen said Jun 12, 2016 19:14:55
As cylinders 1 & 2 are adjacent in the firing order (istr 1-3-4-2 clockwise) and therefore next to each other on the distributor cap the cap is a prime suspect -- but there are other possible causes including 2 faulty plug wires.

So to start carefuly examine the cap inside and out (any doubts at all replace the cap and rotor arm) and check the plug leads for breaks by check the resistance (see NGK's European web site for details https://www.ngk.de/en/technology-in-detail/ignition-cables/diagnosis/testing-of-ignition-cables/ Paul has great video on checking spark plug leads with basic tools but I can't find the link.
You should also try switching spark plugs between cylinders, check the sparking plug gaps (0.8mm or 0.032") and condition and double check the firing order hasn't been switched between cylinders 1 & 2.
All the above assumes your oscilloscope waveforms are putting you on the right path.

These measure prove fruitless i would want to do a compression test or cylinder leakdown test as a cylinder head gasket failure between cylinders is not unknown although this would not explain your ignition secondary scope test results.



[Last edited Jun 12, 2016 19:42:10]
"Rust never sleeps"
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Johan said Jun 12, 2016 20:02:33
Forgot to mention new 02 sensor plugs and a relative compression test was good.
buying plug wires rotor and cap. take maybe a week for the ignition parts to arrive I let you now if the car is a fix.
This is one capture from cyl 1.

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Dylan said Jun 12, 2016 21:28:14
Agree with Andy.
Here's a link to one of ScannerDanner's videos on the free channel. Some basic secondary ignition waveforms on scope.
Belgium, Europe
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Chris said Jun 13, 2016 19:32:53
The capture you posted looks like a no fuel miss. Do you have spark at the plugs? Or at least at the end of the plug wire? What were you HC readings? I'm not doubting a possible problem with the IGN system but trying to rule out all possibilities. If your HC's are high you have u burned fuel but if they are normal with a misfire you possible have injector issues.

Verify your spark the old fashion way with a spark tester or test light and check out your fuel injectors. Look for pintle humps, and at the current ramp as well for both injectors
[Last edited Jun 13, 2016 19:37:21]
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Johan said Jun 16, 2016 15:10:48
The inspection only check CO on old cars like this one in my country. CO reading is 8% need to be 3,5% to pass, spark plugs gets very sooty fast and smell fuel from tail pipe, it is Bosch throttle body injection type with one injection in the throttle body starts easy guess I can rule out leaking injector, ETC reads the same as air intake sensor (IAT) when car has sitting over night (cold).
To bad I can't get HC reading.
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Dylan said Jun 16, 2016 18:24:53
buying plug wires rotor and cap.


So you replaced these parts?
With an ignition problem on one or more cilinders it's 'normal' you're pumping raw fuel through the engine causing these symptoms.



Belgium, Europe
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Johan said Jun 17, 2016 18:45:33
No I have not got the parts will have them next week.
I will came back with information when I have change the parts.
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Chris said Jun 17, 2016 20:35:00
Does this car have the fuel distributor on the air box? I had an 86 golf that had the strangest fuel injection set up I'd ever seen. Had a flapper under the air cleaner lid that was tied to the fuel distributor. Do you have a photo of the engine you can post
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Chris said Jun 17, 2016 20:44:37
Bosch CIS fuel injection. Found a link to diagnose and test the fuel system. http://coupe.pumppumedia.com/korjausopas/03/25_1.pdf. Copy and paste into your browser and check it out.
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AndyMacFadyen said Jun 18, 2016 06:46:06
Chris your car likely had a different system a Bosch Ke Jetronic system which was pretty well standard across all except the cheapest German cars from the mid 1970s to early 1980s,
K and Ke Jetronic systems were very reliable and simple to fix and only fell out of use because they could work that well with an O2 sensor.
[Last edited Jun 18, 2016 06:52:34]
"Rust never sleeps"
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Johan said Jun 18, 2016 10:55:26
Thanks everybody for your inputs, the injection is called Bosch Mono-Jetronic, it is a TBI injection type system it sprays the fuel before throttle plate.
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Dylan said Jun 18, 2016 11:35:57
Nice picture sir. Reminds me of the good old days :-D
Yep Bosch Mono-Jetronic, mono standing for the single injector of course.
I would still focus on ignition though. Don't like that secondary ignition waveform and what's causing it. Kinda confusing that your secondary ignation waveform looks like a no fuel misfire, like Chris mentioned.
Do you have other scope waveforms?
[Last edited Jun 18, 2016 11:45:27]
Belgium, Europe
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Johan said Jun 18, 2016 20:30:43
This is Cyl1


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Johan said Jun 18, 2016 20:38:10
This is the Hall sensor in distributor blue line hall sensor and red line primary voltage.



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Johan said Jun 18, 2016 20:46:36
Primary voltage and Hall sensor



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