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Misfire, timing light question

Hi all, im working on a family members car, and id appreciate any advice you can offer please :)

The problem.
The car all of a sudden is not running properly, sounds odd, hard to start, vibrates more through the whole rev range and if left idling it stumbles all over the place

Engine error code 301 cylinder 1 misfire.

I have two primary questions

1. Is the front 'cylinder' definitely 'cylinder' 1.

2. Timing lights. Why do my timing strobe lights not work on the RX8? I tested both guns on my motorcycle so i know they work, i put it on each of the leads in turn in both orientations, i get nothing??? Is this normal? It would have been real handy if it would work.

I tested the plugs with a multimeter, the resistant on both is identical and there are no shorts to earth. The same goes for the coils, i tested the resistance on all pin combinations and they are identical to each other. Leads seem fine too. The top plug was sooty, the the bottom plug full of sludge, both now cleaned.

The maf seems ok, as the engine stumbles when disconnecting and if i open the air box i get various engine errors relating to airflow. Plus if this was the problem cylinder 2 would also misfire?

The exhaust fumes smell of sulphur but it never has before, i assume this is normal with unburnt fuel now in the exhaust system?

I was going to disconnect the HT leads in turn whilst running to isolate the problem further but now its not bloody starting at all, possibly flooded.

I assume as the error is only on cylinder 1 it will be an isolated problem, so various sensors that affect both 'cylinders' will not be the problem, as if they were both would be misfiring?

Id love to get the timing light to work on this car to rule out the coils. Injectors and compression next target?

Thanks all.

Quote:

Originally Posted by danielbb (Post 4366010)

Need the year and mileage of the rX8

Also it is quite common for the Coils to fail.
This will cause hard starts and poor performance and idle.

A dirty Maf and or ESS will cause these problems as well. Both are easily cleaned.

By the way only the Lead Plugs fire on during cranking. If you've attached the timing light to the trailing leads you will not get anything.

Sounds like the car is flooded now.

Search deflood procedure

Are you aware that this is not a piston engine?

Misfires are almost always ignition, however can be a number of other things.

https://www.rx8club.com/rx-8-discuss...t-here-202454/

Quote:

Specific Issues:
- Misfires are shown by a blinking check engine light (CEL), and are usually caused by a failing coil, failing plug wire, and/or failing spark plug. They can also be caused by cat failure, engine failure, vacuum leaks, fouled e-shaft sensor, dirty MAF, missing intake screens, aftermarket intake, failing intake valve actuators and a few other items. Start here for diagnosis: https://www.rx8club.com/tech-garage-...t-here-222280/

Quote:

Importance of Ignition Health:
************************ READ THIS!!!! ************************

One of the most often overlooked or ignored parts of RX-8 ownership is the health of the ignition system. This includes the ignition coils, spark plug wires, and spark plugs. They fail. Often. So often as to be critical parts of regular maintenance.

Before I detail why, check out the first post of this thread here: The impact of old coils, wires, & plugs - RX8Club.com (owner's post here: [FEELER] Spring 2012 MM Tuning / Dyno Day @ Speed1 Allentown (formerly KDRotary) - Page 8 - RX8Club.com)
The owner's power dropped from 199whp to 172whp JUST from failing ignition. That's a 13.5% power loss!

Do I have your attention now? Good.

Mazda officially lists the plug wires and plugs as part of regular maintenance, but not the coils. Many dealers STILL don't know how easily the coils can fail. And they fail about the same time as the wires and plugs, which is about every 30,000 miles. Some can last longer, some shorter, and it's more related to your total RPMs than it is to your mileage. Highway cruising is easier on the coils than spending a day pounding around a race track.

When coils fail, they don't suddenly shut off. They start producing weaker pulses scattered among strong ones. The rate of weak pulses slowly increases and pulses start getting dropped entirely, which is where misfires start. All of this means that you aren't burning all the fuel and aren't using all the air that the engine pulled in for that combustion, and it unburnt fuel and air gets dumped into the exhaust, where it happily ignites with the presence of plenty of heat. This saturates the cat in both fuel and heat, and will rapidly kill the cat (A $1,300 USD replacement). Continuing to drive on a failing cat will add other problems such as engine damage and vehicle fires. I am not exaggerating, this can happen with just a single cat failure!

Plug fouling and wire failure is largely the same result, since all 3 pieces are needed for a complete spark. Foul the plug and it doesn't matter if the coil and wire are good. Break down the wire and it doesn't matter if the coil and plug are good.

Symptoms of ignition failure include: Power Loss, mileage drop, unstable idle, bad idle, inability to idle, shaking at idle, unstable high rpm, misfiring, flashing CEL, coughing engine, glowing cat, flooding, inability to start, inability to pass an emissions sniffer test, and just about anything you can think of where a weak or missing spark causes problems.

And if one fails, it will cascade to the other trio on the same rotor. A plug that can't fire will start fouling the other. A coil that can't fire a plug starts wearing out rapidly (if you want to test this, just unplug a wire from a plug and run the engine for a while. The coil will rapidly fail. Not unique to rotary engines)

Why do coils fail so easily?

This is largely because Mazda opted for cheap coils because of RX-7 owner complaints about how expensive their coils were. The RX-7 coils lasted much longer though. So Mazda went cheap, and so we have to replace regularly. And you can't compare to piston engine coils. A piston engine with the same setup of 1 coil for 1 plug has an average RPM of about 2,500rpm and the coil is firing every other revolution, so the coil is firing about 1,250 pulses per minute. Our rotary has an average RPM of more like 4,000rpm, and each coil fires every revolution, so about 4,000 pulses per minute. That's a bit over 3 times more. Even a piston max RPM of about 6,000rpm vs our 9,000rpm makes the difference 3,000 pulses per minute vs 9,000 pulses per minute, or 3 times as fast.

If our coils would last about 3 times longer, you are talking an average of 90,000 miles.

So keep your ignition healthy!

Post #5 in that thread has some useful information about the engine that might help you.

The car has done 50-60k ish, a 2005 RX8 231 UK spec

Yes im aware its a wankel engine. I'm aware of this cars ignition issues too.

The car was running with the timing light on it. and i was revving through out the rev range. I got nothing at all, can the pulses be so weak it wont register? is that typical? Has anyone successfully used a timing light on an RX8? It could be that the timing light works fine on new coils and not older coils?

If it were my car id of upgraded the ignition stuff as soon as i bought it, but you know what normal non enthusiasts are like. They wait until problems occur.

Thanks all, i'm just going to tell him to do what i originally told him when he bought it. I wish people would listen.

Dont think ill be able to unflood it, until its sorted. Deflooding is a nightmare even with a healthy engine lol.

Thank you all.

I can confirm it was one of the coils. Even though a resistance check would suggested it was fine. I bought a set of 4 for £70 on ebay, non oem. Seem fine so far.

:)