dsky

wel kids, after two weeks of rough idle and pinging, i've found my problem,
lets re-cap:
1. i wash the engine compartment.
2. black smoke, poor idle, engine stall.
3. with 90K on the orig optispark i determine it must be bad opti spark (it was filled with water)so i;
4. replace opti, wires and plugs and while everything is out, the water pump. then assemble.
5. pinging on start rough idle, alomst bucking while running at speed.
6. bring car to chevrolet, tell them to put it on the scope, tell me whats wrong.(they also install 2 o2 sensors that i supply.
thier diagnosis....FOULD PLUGS< EVERYTHING ELSE IS OK!...i tell them i just installed bosche platinum, they dont foul. they stick with thier diagnosis.
5. get home ,pull plugs, they are as pretty as when i put them in.
6. replace fuel filter and PVC valve , also new water temp sensor.
7. bring car to "corvette specialty shop"
they have never seen a car act this way. with all the sensors sending info within specs to the ECM, the ECM must be bad right?
wrong.
8. i replace ECM, same symptoms.
9. i think to myself have the laws of physics stop exisiting in my engine compartment. i ponder, i must have done something wrong.
10. so i dissassemble entire project.
11. i find my problem.

so ya know that little splined shaft that connects the opti to the cam, know how it is idiot proof because of the key(it can only go on one way)? WRONG with only the slightest bit of effort, you can defeat the keyway. i was off one spline, so with 14 splines, the timming was advanced almost 25 degrees. cool huh? the engine still ran!

the moral of the story, make something idiot proof and they'll build a better idiot!

thanks for help though guys, because the one thing i have learned is how that freakin system works, and that pretty valuable information

regards
doug

PurpleC4

Congratulations on finding your problem. Some dealerships are good, but most are just parts changers (as you have found out). Most answers can be found here on the Forum. A little time and patience will reap dividends. Good communications as to what you have done, and what the symptoms are ~~~ really helps speed the process.
Purp

dsky

a lot of good suggestions came from this group, once again, thanks guys!

Hendej

Wait a minute. A Corvette specialty shop and GM dealer both failed to do a routine check of the timing on a complaint of pinging? Amazing! You deserve a refund. Two refunds! The moral I get from this is don't always trust the "expert opinion" you pay for (like you learned).

jfb

I had pinging and on level road, bucking and I found the timing too far advanced. I told the mechanic I found what he couldn't. At least tell the two places you took it to what you found so they get the benefit of your perserverence.

dsky

in all fairness the corvette shop, assumed i did the job correctly. while they said it was the ECM, they also said it was a timimg problem within the ECM.
the chevrolet dealer took the shotgun approach, they wanted to replace everything for $1,900.00 (ya can always tell when someone is confident of their diagnostic skills)

so the end result, wit 93k on the clock, the car breathes fire now!

regards
doug