cold timing a 1999 7.4l vortec

[gertsch]

So my dad has replaced everything on his 99 burb with 7.4l. He had to replace the distributor because the tabs broke when reolacing the cap. He went through and cold timed it likebyou normally would. No1 at tdc timing mark at 0 onthe compressiin stroke. It would fire up and Iidle great but any hard throttle It would bog out annd die. It doesn't matter if it's in park or gear. Ive heard a wire that is suppose to be disconnect for setting up timing. Is this true? Is there something he has missed? Any help appreciated.

 

[Tacoma]

on prior models there's a... tan wire if I remember, that has to be disconnected prior to setting timing. But that's for TBI stuff. I would suspect that they generally kept things the same as the architecture of the big block stuff didn't change too much, and the Vortec setup wasn't that huge a tech leap. May want to verify that though hahah

... and apparently that is NOT the case w/Vortecs, no wire to disconnect first.

Only found this: http://www.pacificp.com/forum/viewtopic.php?t=7057&view=next&sid=007a6eac919ef737fdf09a6a1aa4121e with any detail so far.

 

[gertsch]

That helps a ton I will verify that been done. Thanks Tacoma!

 

[boogie_4wheel]

If it is like the small blocks, you will need a scanner to see the variance on the crank/cam correlation (timing).

On the 5.7L Vortec (I'm going completely from memory now, got rid of mine almost 3 yrs ago and didn't have to do this for at least 5 years), the rotor needs to be +/- 2* TDC or it will throw the CEL. After I replaced the dist on mine I got it close and it would stumble at startup for a few engine revolutions till the computer caught up with the abnormality. I took it to Tunex to get it dialed in for (I think $50). If I remember correctly it needed to be dialed in (rotating the dist left/right like you would to time an older rig) while spinning the engine at 1500rpm. I do not know if the 7.4L is the same way; do a search online for crank cam correlation for the big block and see if there is a procedure...

 

[gertsch]

Thanks that is good to know. I will be working on it tonight so I will post up my findings

 

[gertsch]

So I pulled the dizzy. It was off a few teeth. So I followed the procedure Tacoma posted. It worked great! Thanks Tacoma. All that's left is to have it finished of like boogie said. My scan tool won't do it so the old man will take it in tomorrow to have it dialed in.


thanks guys!