Steve85

I decided to drive the vette to work today and just a few miles from home check engine light comes on and the car will idle but not accelerate. So I grab a piece of wire and pull code 33.

I called work and my friend looked up code 33, MAF sensor signal high. So we decided the thing to do is unplug the maf and let the ECM substitute values. Well, that didn't really work, still zero throttle response but I manage to drive the remaining 20 miles at 3100 RPM where it ran OK.

We pulled the schematics, I find it very helpful to work in the bay right next to our Corvette specialist. He's on vacation but the books are just a few feet away. No power to MAF so my doomsday mind goes to burnoff module. No power to burnoff module which is powered through the 10AMP gauges fuse. Fuse was blown, this fuse does not actually power the gauges, my dash was always fine.

With a handful of fuses we start connecting and disconnecting. Turns out that the overdrive relay was shorted, we noticed the light would come on for a second then the fuse would blow. Taking the burnoff module out of the loop reduced the draw enough to check other devices on the circuit. We disconnected the OD relay and all was good, except for that off idle flat spot....

We started throwing timing at it. And at 7:45 tonight there were four very experienced techs wondering how a small block could be taking 55* of total timing, not pinging, and now running like mad. It's like a whole new engine, throttle response is quick and amazing. I always knew there was power, but this is great. So sparked was the conversation about the 12* timing mark differences between some 400 blocks. You might remember that Jesse and cork built identical motors and ran within a 1/10 of a second with a 12* difference in timing. Even if that is the case, 43* is still alot of timing.

I tried lugging the engine in 6th to force a ping and heard nothing. It's a little hard to swallow but if that's what it wants, that's what it wants. I definitely need to make sure my knock sensor is in good working order though.

So, on the way home, as I passed by the place I was stuck in the morning I dropped into fourth at 70 and found myself celebrating at 118 shortly thereafter. Very shortly therafter.

I think I'm glad I broke down this morning :confused:

NightRyder

woha, thats amazing, atleast to me.

vinnies87

:eek: :crazy:

CORKVETTE1

how do you know its 55 degrees timing :cheers:

Curveit

The outer ring on your harmonic balancer may have slipped, giving you a false reading. You might want to check TDC on #1 cylinder with a tool(piston stop or such) and see if it is correct.My $.02.

:chevy

esapee

Is Your Vette -85?

CORKVETTE1

a piston stop will stop it at some degree before top dead center will we know this degree no so that is useless the only way to know for sure with out pulling the heads and or motor out of the car is to pull the ballencer and lay it up to a known good ballecer to see if it spun any and 12 degrees is not that much to spin to the naked eye not to mention do we all remember when jesse used a piston stop on his motor and the stop broke off in the cylinder and it took him hours and hours to get it back out and i seem to remember a wrench going through a wall at some point also :cheers:

Steve85

As read with a MAC tools timing light, against an ATI 360 degree marked damper. I'm curious why you ask...

edit:Just read the above posts, I don't know that this damper could seperate like that. What you guys speak of did happen on my old motor with the stock balancer. Took me some to figure out why my readings were out in left field.

Talked to another tech at wotk today, in his experience (20yrs with chevy) he had two similar hot rod motors, one that took 58 degrees and one that took 45. "Turn'em till they ping then take out 4 degrees" These were either oval or dirt track motors he and a friend used to run, 434's I believe.




[Modified by Ski2Tee, 7:44 PM 12/12/2003]

CORKVETTE1

the only way to check total timing on that would be on a wheel dyno so you can load the car and then check the timing other wize you are not checking right total timing right :cheers:

Steve85

I guess the question is then, what am I seeing when the throttle is cracked and how will it differ from on the dyno? Would it generally show more or less?

CORKVETTE1

you are looking at no load there are about 24 different tables the computer go through from no load to full load so a static timing test like you did tells you nothing :cheers:

CORKVETTE1

on the dyno it will be in a full load enviroment so you will be seeing how much timing you actually have :cheers:

CORKVETTE1

these cars arent like a carbed car to tune if it was only that easy :cheers:

Steve85

Thank you!! I now understand better what goes into tuning these things.

Funny how you can spend years diagnosing driveability concerns on various engine control systems and not ever have to be concerned with such details necessary for maximizing output.

CORKVETTE1

BUT IT IS FUN OR WE WOULDNT BE DOING IT :cheers: