bad spark plug coil

[cutrell3]

Chris,
Hey! My name is Trey. I have a 94 SVX LS. I have a long standing problem.
I have what seems to be an engine miss. It happens when the car is at an idle every so often but most of the time it at low rpm's in the highest gear.
Ex: If I'm decreasing my speed from 60 or so, once a get under 3000 rpms, if I press the gas slightly so that the car does not downshift I usually get a very noticable skip(the car jerks like a bad miss). I've taken it to several dealerships and several ind. mechanics. They all feels it's one of my coil packs but can never tell which one it is. Is there any way to investigate this further. I don't want to replace three or all six coils and it be something else. Like I was saying, this has been going on for years. It has been at the same point for a long time, as to say that it isn't progressive anymore. Hasn't gotten any worse. It just stinks not knowing how to correct it.

Thanks for your help.

[Earthworm]

Does it sound like a backfire?

Chris (GreenMarineSVX) and I both have Stebro exhausts and the method you describe will cause a backfire in the exhaust.

If you believe you have one bad coil you can get 1 spare (with the longest cord) and replace each coil one at a time to see if the symptoms stop.

The ECU is supposed to be able to detect a misfire on each coil.

[cutrell3]

Thanks for the help. It's not an exhaust backfire. It's more of a jerky type skipping that you can tell is coming from the engine. The excuse I got with the ECU not picking it up was that it usually only does it when the car is in motion under force. It especially does it going up hill. I've also been told that it is not completely bad and just missing connection some of the time so it's not being picked up.
Are you saying that I can get the coil with the longest cord and use that one to test replace all of them until I find which one is bad? So the only difference between 1,2, and 3 is the length of the cord? Good to know.

On another note; I am looking to get new exhaust. Do you recommend the Stebro. How is the sound compared to flowmaster 80 or the motorsport warehouse package with the magnaflow?

Thanks again.

[Beav]

The $80 answer is..... only OBDII equipped vehicles employ misfire detection.

Have you had the spark plugs changed since this all began? A cracked or worn plug, a worn coil to plug boot, etc. could cause the problem.

Originally posted by cutrell3
On another note; I am looking to get new exhaust. Do you recommend the Stebro. How is the sound compared to flowmaster 80 or the motorsport warehouse package with the magnaflow?

Thanks again.

I can't speak for all custom exhaust set ups but of the few I've seen, the Stebro had the cleanest sounding tone. All the others were a vast improvment over stock but the Stebro lacked the typical raspy ricer exhaust characteristics. Like I said though, I've only heard about a handful of "custom" exhaust systems including Magnaflow.

I like the Stebro HP gain and exhaust note.

I like the Magnaflow price MUCH better.

For now the stock system will do. I'm thinking about removing the resonator, all the stock cats and replacing w/ one high flow cat.

[SilverSpear]

Originally posted by cutrell3
Chris,
Hey! My name is Trey. I have a 94 SVX LS. I have a long standing problem.
I have what seems to be an engine miss. It happens when the car is at an idle every so often but most of the time it at low rpm's in the highest gear.
Ex: If I'm decreasing my speed from 60 or so, once a get under 3000 rpms, if I press the gas slightly so that the car does not downshift I usually get a very noticable skip(the car jerks like a bad miss). I've taken it to several dealerships and several ind. mechanics. They all feels it's one of my coil packs but can never tell which one it is. Is there any way to investigate this further. I don't want to replace three or all six coils and it be something else. Like I was saying, this has been going on for years. It has been at the same point for a long time, as to say that it isn't progressive anymore. Hasn't gotten any worse. It just stinks not knowing how to correct it.

Thanks for your help.

change them all in my opinion, sooner or later they will start defecting each in a row

Originally posted by SilverSpear


change them all in my opinion, sooner or later they will start defecting each in a row

Not the cheapest but definately the most fail safe way to go. I would also want to me MORE than sure that it was a coil before I start throwing x amount $100 at the car too.

[TomsSVX]

get new plugs for the car and see if that helps. if not then buy a single pack and try it on every cylinder until you find the right one. Once the bad one is replaced keep in the back of ur mind that u should buy new ones somewhere down the road and when u have the $ get them. That would be the most cost efficient and effective way to attack this problem. 9times out of 10 the dealer guys know what they are doing but i would go w/ new plugs first (cheaper).

[cutrell3]

Thanks for all your help. I have had the plugs replaced with no affect. I'll start with the one coil and move on from there.

Thanks also for the exhaust advise.