torchvette10

Hi guys,
PLEASE HELP ME! MY C5 IS DRIVING ME CRAZY
does anyone have a diagram with the ignition wiring? I searched the forum but I did not see it.
My car has been running like crap for 5 months already: changed plugs, wores, coils, MAF, checked vlave springs, bought HP tuners to scan it and nothing changed. I even got two different tunes in the car from reputable tuners as I thought it could be tune related and still nothing. Tomorrow we will run the car with open headers to see if the problem doesn't come from a clogged cat, who knows. The car throws no codes.
My mechanic said that everything sounds like an ignition problem. You can hear explosions in the exhaust from time to time, scary he said it is unburnt fuel. According to him, it canbe an ignition issue.
My right exhaust tipis clean. So I guess less gases goes through the right exhaust.

Please if anyone has a PCM wiring diagram for the ignition system, PLEASE SEND IT TO ME. This car is driving me crazy! I love it but Iam getting tired of spending countless hours trying to fix an issue and still having it. It cost me a lot of money in parts and labour and I can't stop now! I need to find out!

thanks in advance!!
Dave

torchvette10

PLEASE GUYS!

vermjpv

I would suggest buying the service manuals.

torchvette10

Thanks, That's whatI will do this summer when I come to the USA. I can't get it around here!
In the mean time, I can't figure out the problem I have, it is driving me crazy
Have a nice day

jimcork1

see private Email.

rhoeven

A few suggestions:
Are all sparkplug cable boots sitting all the way onto the spark plugs?

Check the ground connection of the ignition coils going to the rear of the engine block (driver side) Due to block vibration, some of those wires tend to break internally creating intermittent contacts and misfires.

Hope this helps

Roger

torchvette10

I will check that, thanks for the advice! I already checked the wires and they are all sitting. Everything is fine on this part. However I willneed to pay more attention to the grounds, I willdo it tonight
James (Jimcork1) sent me a PM and he will foraward me some wiring diagrams! Thanks again, I hope it will help.

I will keep you guys posted as this issue has already cost me a lot of money and I don't want anyone to go through that again.

SpeedyZ

Have you looked for the common wire chafing problem where the wiring harnesses drop over the back of the block right at the rear of the intake? Have heard several people say they have had coil (primary) wires to wear through and short at that location. And shorting coil wires could cause backfiring like you described.

torchvette10

Hi,
thanks for the advice! I will look into it again but from what I have seen I did not see anything wrong! I will check that very meticulously again
We ran the car with open headers an hour ago to see if it was not a clogged cat but it did not fix the problem.

dgrant3830

When I was last living over there back in the 80's, no unleaded fuel was available back then. Do you have it now? If not, the cats and O2 sensors are probably garbage.

torchvette10

Yes, I am running 93 octane. The fuel is good now. I checked the 02 sensors through HP tuners and they work fine, and we inspected the cats today (they look like new because they almost are )
We then tried runnig open headers but the issue was the same.

My mechanic said it must be ignitionrelated. Some electrical issue, don't know yet. I will check every single thing realted to ingnition. If you know anything thatcould be checked on the ignition system let me know (new plugs, wires, coils already on the car).
I checked the wiring harness but it looks fine. Are there any measures to take?

Thanks a lot guys! This forum is really great!

dougbfresh

I bet you have an exhaust leak causing the popping in the exhaust.

SpeedyZ

Another thought, if you are hearing "explosions in the exhaust" you should be able to pull one injector plug at a time to see if you can isolate it to a single cylinder. Might help to isolate the problem.

Can you give us any more history? Did this start all of a sudden? Had it been running fine before? Any mods? Any recent work done before the problem started?

torchvette10

When I try to remember, it happened several months ago when I was getting onit on the highway. It started kind of misfiring.
Since then the problem has always been present.
Basically here are the symptoms:

The idle is sometimes unstable (but sometimes it is stable)
When I try to get on it, under heavy load, the car seems to be misfiring. It feels like it has 200HP less than it should. Moreover you can hear
explosions when getting on it and the car smells gas really bad.
It seems that there is unburnt fuel.

And one more thing that has been noticed is that the right tip of my 4 tip exhaust is cleaner than the others. It tends me to think that the issue is located on the right side somewhere.
We changed many parts. Today we checked the plugs again and theylook fine. I really don't know.

The mechanic said it must be ignition related. He said that it sounds like the car doesn't burn all the fuel, and that's why when you let it idle, you can hear explosions from time to time (which according to me results from bad ignition, unburnt fuel)

Let me know what you guys think (PS a compression test has been done as well, it is fine and valve springs have been checked)

torchvette10

Oh and headers have been installed about a month before the issue started. But I put over 2000 miles on the exhaustsystem when I installed it and had no issue. So I don't think it is related to this mod

SpeedyZ

Here is the ignition coil wiring diagrams and fuel injector diagrams for a 99 C5 Pretty much just wires directly to the PCM but there is a few connectors in between.

http://corvetteforum.shelor.net/Diagrams/Misc/

torchvette10

Thank you Dale, thank you so much!!

SpeedyZ

Thought that may help