My '05 GT has developed a bad misfire. It happened once before and the dealership was unable to solve it. They suspected it was a coil going bad, but didn't actually replace anything. That was a couple months ago and the car has been fine.

Over the past few days the temperature outside has gotten much colder. The past two mornings it's been -14 and -17 when I've left the house. Yesterday the car had a bad misfire for several minutes before it would idle normally. When I drove home, it misfired the whole way (I only live a mile from work) with the CE light flashing and a friend told me my car was blowing sparks out of the exhaust the entire time. I never saw it because, by the time I got home, it was running normally.

This morning it started, sputtered, died and wouldn't restart. I took my wife's car to work. Over lunch, since it had warmed up to maybe 5 degrees, I tried the car again and I had the same misfire that I did yesterday. I drove it a couple blocks, the engine started running normally, but the CE light was on permanently. I read the stored codes, which (go figure) were for misfires.

I have new coils and wires coming. I just replaced the plugs not two months ago. I'm not going to drive the car any more until those parts get here. What I'd like to know is what those sparks could have been. My friend said that whatever they were, they stayed glowing on the ground until he ran over them. I have a guess, but I'd like to hear any other suggestions.

Thanks.

 

pieces of the cat

 

yeah its your plugs and coils, replace em ASAP...misfires arent good

 

As I said, the new coils are on the way and the car will sit until they get here. The plugs are new. I'll check them and if any are fouled I'll replace them too.

I should have picked faster shipping. :P

The dealer started rattling off the things that could be damaged by the misfire, and it was a pretty startling list.

 

Spitting burnt kitty pieces out the @ss is never a good thing!
Yep..........wouldn't even drive it anymore until the new coils and plugs are in.
How did you read the codes.......with what? I really want to know if it will read exhaust temp.........you might be needing that.

 

first off how many miles on the car

im guessing its either a loose plug wire (I got the misfire code myself once after changing to nology wires without making sure they were on all the way)

or bad coil grounding out to the mounting frame, to check if it is the coil grounding out, take them off the metal bracket and look for discolored or black marks like burnt color on the metal bracket, that will tell you if the casing integrity of the coils has gone. our first gen coils dont cope well with the heat and the plastic gets hairline cracks and grounds out the spark right there causing the char color.

and both cause the engine to load up with unburnt fuel, getting caught in the cat and iginiting there, you could pull the second O2 sensor and see if there are heavy carbon deposits on it. in theory it should only be discolored a dark black with no chunks on it, but there still may be some.

hope i help some

 

No kidding it isn't! I'm just hoping that the few miles I drove it in that condition didn't damage anything internal.

I drove the car to an auto parts store and borrowed their reader. I have one, but it's not CAN compatible. Argh.

 

The car has 32k on it.

Exactly what's wrong with the coils or wires is academic at this point, because both are getting replaced. Still, thanks a lot for the tips.

The cat's getting replaced with a high-flow one anyway, so it's not a big deal if it's burned up...and it sounds like it probably is. If the O2 sensor is gross, I'll replace it as well.

 

coils/wires/plugs are the main cause of misfire around here! The sparking is prob pieces of the cat (as mentioned above) so it's prob clogged and maybe even glowing red when the car is running so with the new wires/coils and high flow cat everything SHOULD b ok

 

Jesus, Nick.

If I'd have known you'd become a statistic I wouldn't have let you run my car!

 

^huh?

 

it is you coilovers!!!!

ok. really likely a coil or two.. or a loose plug wire..

usually the lower front one. ask me how i know.

beers

 

Well, now you know the price I pay for being faster than you.

 

I could guess, but I'll bite. How do you know? :D

 

it just happens often..

location, location, location..

btw, hows the stance project coming?

beers

 

Rather than derail my own thread, I'll send you a PM.

 

I replaced the coils yesterday, and the car is running fine again. I didn't replace the wires because it looked like it'd be easier to do if I could get under the car. I was short on time and it was cold outside.

Two of the coils had white marks on them, where they contact the bracket. I have no idea whether that's a sign of damage. The other two looked normal. I need to find a way to test them so I know which ones are okay spares.

I removed the flexible intake tube before the throttle body to get to the ocils, but before I broke two of the three 90deg elbows that connect to the vacuum lines. They were more brittle than anything on my 22-year-old MR2, which really annoyed me. The dealership wanted $10 each, had none in stock and wanted me to prepay for them. Obviously they were ridiculous on all three counts. NAPA had some that fit, for about $3 each.

The car started immediately after I buttoned everything back up, and I took it for a test drive. It coughed once, without registering a fault, and there was a thin cloud of smoke from the exhaust when it happened. My guess is that it was a piece of cat the car coughed up. The cat is probably very badly damaged at this point, and I'll be ordering a high-flow one this week.

That's my story. I hope it helps somebody else.

 

https://www.rx8club.com/showthread.p...t=coil+testing

beers

 

A mechanic friend of mine tells me the white marks I saw on the coils were typical signs of arcing between the coil and the bracket. Note that this is a mark you will only see by removing the coil.

 

^^ no reality to that...

 

I'd be happy to hear a second opinion suggesting what the white marks on the coils, and corresponding hot spots on the bracket, are signs of (if anything).

 

the white marks and spots on the bracket are caused by heat. They do not indicate anything other then the coils get hot... which they all do.

 

Yep running rich.

Sounds like it was a little flooded.

The Ap from MM will solve your problems or the coils from BHR

 

Yah, but weren't you faster than me in the MR2?