LT5 wont run with all cylinders

[Mika73]

Originally Posted by 95ZR1

What did you do, put leaded gas in that car? I wonder why they kept saying 2 and 7 weren't firing right if the cats were bad.

First question: NO. They dont even sell leaded gas anymore here at Finland. And I didnt use diesel fuel either.. And then back to business.

I dont know why 2 and 7 didnt firing right and O2 reading was max.

But everything looks normal after cats were removed.. Engine did run ok with headers only and O2 sensor reading was normal.

I dont know why. They think that I got bad chip that did kill my cats.

I dont know why this all is happening..

Those RT cats did last two days and 120miles.. Its quite expensive..

[Mika73]

Ok.. Maybe its not catalysts...

He did looks inside catalyst and can see through it.. It doesnt look bad.

Maybe it runs now ok when there is no exhaust pressure when there is headers only..

[Kevin]

This is just wierd. Maybe e-mail mark haibeck or Mike Ebert and see if they can help

[W i l l]

Mylzi,

My vote is that there was an electrical gremlin somewhere letting the two cylinders run rich. It could be coincidence that everything went back to normal when the cats where removed. Then again I may be way off base. It just seems that all the facts don't add up. I would ask the 'mechanics' to put the cats back on and see if the problem reappears.

Good luck!

Originally Posted by Mika73

Ok.. Maybe its not catalysts...

He did looks inside catalyst and can see through it.. It doesnt look bad.

Maybe it runs now ok when there is no exhaust pressure when there is headers only..

[Mika73]

I have emailed to Marc. There is not good spark on cylinders 2 & 7. And maybe thats why O2 reading did show max. But it runs when cats & exhaust is removed. Maybe that not regular spark is enought when there is no exhaust pressure at all when cats and exhaust removed. I been told that usually spark has kinda pulse.. My spark comes and goes, its not regular.
Mark thinks that there might be two bad coils, but Corvette service here says he did change coil places.. and it didnt help. I have no idea whats wrong.. Car has been at service 4 weeks.

[Tyler Townsley]

Originally Posted by Mika73

I have emailed to Marc. There is not good spark on cylinders 2 & 7. And maybe thats why O2 reading did show max. But it runs when cats & exhaust is removed. Maybe that not regular spark is enought when there is no exhaust pressure at all when cats and exhaust removed. I been told that usually spark has kinda pulse.. My spark comes and goes, its not regular.
Mark thinks that there might be two bad coils, but Corvette service here says he did change coil places.. and it didnt help. I have no idea whats wrong.. Car has been at service 4 weeks.

Have him perform the checks I recommeded with you watching or a friend who is knowledgable about car ingnition systems. I agree with Marc H its something in the 2 7 spark ckt. You take a known good ckt from coil to plug and place it in the bad ckt on item at a time until the defective item is found.

Tyler

[Mika73]

Problem FOUND:

There was broken valve spring..

I heard from Marc that this is really uncommon. He saw one 5 years ago..

[cuisinartvette]

Boy, you sure had to work to find that one! Good luck on the fix

[Z Factor]

Originally Posted by Mika73

Problem FOUND:

There was broken valve spring..

I heard from Marc that this is really uncommon. He saw one 5 years ago..

I have never heard of one breaking until yours. Any ideas as to the cause?

[Patton]

Wait,... on BOTH cylinders?? Talk about "winning on lotto"

Congrats! Boy do I know how great seeing the light at the end of your plenum feels.