Melted COP
December 12th, 2024
Burned out and melted ignition coil
Suzuki Splash – Diagnosing Intermittent Misfires With No DTC’s
December 10th, 2024
What’s the problem?
This Suzuki came into the workshop with an intermittent misfire. It wasn’t evident on tickover or when I’d snap the throttle while stationary. But when I drove it any distance, I could feel it. Okay, so that’s the customer’s complaint confirmed. The next step was to connect a scan tool and check for diagnostic trouble codes (DTCs).
No codes?
Despite the misfire, no DTCs were stored. With no codes, a different diagnostic approach will be required to prove the fault. I’m suspicious of an ignition coil but I want to prove it to be sure.
What can cause a misfire?
Ok, so what scenarios are running through my head right now? What else other than a failing (COP) coil-on-plug could be causing this misfire? I need to consider the basics that make this engine work, Spark, Air, Fuel, Ignition.
- Failing fuel injector
- Ignition coil (COP)
- Failing O2 sensors
- Coolant temperature sensor
- Mass air flow sensor
- Fuel pressure
- Old/failing spark plug
- Low compression
Sometimes luck is a great diagnostic tool
While im deciding what to do the engine starts to misfire while at idle. I’ve already got the Picoscope set up so it’s the perfect time to use the Rotkee coil-on-plug probe. It takes time to set it up. Some double sided tape is needed to attach it to each coil but it works well. I should make some clips to hold them in place.
After setting up the probes, the engine continued to misfire, and I captured the perfect misfire waveform. The image clearly shows a misfire on Cylinder 2. To confirm I move the coil to cylinder 4 and the misfire follows it. I am now confident that a new ignition coil will fix the problem.
Conclusion
I had diagnosed this car over the phone from the description the customer gave. I had a gut feeling it was a failing COP. I could have ordered a set of coils and plugs. Then fitted them to the car without even plugging it in or driving it. And I would have been right. But without proof I would have possibly cost the customer a lot of money unnecessarily. I like to test before I buy anything. Even it that means holding on to the car for a longer period.
Also I got lucky here. This car wasn’t initially misfiring while stationary. But sometimes luck is your best friend when diagnosing a problem. Below is a copy of the waveform after the fix.
No door locks?
December 9th, 2024
Door locks and electric window inoperative on the drivers door of this Alfa Romeo. This is very common issue with door wiring looms. Especially on older cars from doors been opened and closed thousands of times!
VW Passat – When lights are out, It’s not always just a bulb
August 6th, 2023
What’s the problem?
A Volkswagen Passat came in with a warning light on for a bulb out and a non-functional Daytime Running Light (DRL) system. The customer had already replaced the bulbs, but it hadn’t made a difference. The only other information we had was that the car had been in a minor accident with some light panel work done, but the warning lights didn’t appear until well after the repairs
Visual checks save time.
A quick look at the front of the car and I noticed a slightly ill-fitting bumper. Looking through the grille, I could also see a wiring loom which was running on the wrong side of a panel with the insulation torn.
The next step was to expose the loom and see what was happening inside. As suspected, there were broken wires.
My next step was to verify that the exposed wiring had the correct powers, grounds, and signals. I performed this test using a simple test light and a multimeter to prove out the integrity of the circuit.
All the wiring proved to work just fine so its just a case of connecting these wires and the job’s done.
Conclusion.
I suppose the conclusion here is pretty simple, find broken wires and repair them – now everything works. But the lesson is looking for clues where previous work was carried out. It’s unfortunately very common to find problems like this that were created during past repairs.
